Thursday, December 27, 2007

Pressure and Stress in the Earth's Crust

Mammoth Creek, east of the Sierras, exhibits a N-S Anomaly, with Steam and active Faulting

Pressure and Stress in the Earth
All of you are familiar with the term pressure, since your faucet delivers water to you because of the pump pressure. Whenever the pump fails, or whenever too many neighbors use the water at the same time, you hear a gurgling noise from your faucet, and you phone the water company complaining of “Low Pressure”.
The use of the term stress may not be so recognizable, since it is used to connote bodily discomfort, how you feel in your auto on the freeway, or poor relations between family members. The usage of pressure and stress terms in the Earth’s Crust is defined below.

When you are lucky enough to drill a water well which has artesian flow, you have encountered a rare occurrence of fluid in rock- which is being squeezed by an Abnormal Force, causing water to flow out on the ground on its own impetus (no pumping necessary).
Both pressure and stress are defined by the force, F, exerted over an area a (either static or dynamic):
P, S = F/a,
usually in pounds per square inch, psi, but also in dynes/square centimeter, or Newtons/square meter- in universal physical units. Notice that force or weight, not mass, is the entity measured.
The convention for Petrophysics or Rock Science is to categorize pressure as being a fluid measurement and stress as being a solid force exerted over an area of rock. These should be distinguished in three categories:
a. The fluid pressure is only exerted in the porous part of the rock (usually no more than 30% of the total volume), and it is exerted omni-directionally- that is, in all directions, since fluid works outwardly from a source without regard to direction. For Static conditions at equilibrium, this pressure is determined by the height of a column of fluid, e.g. .433 psi./foot x height for pure water (unheated and containing no minerals- one atmosphere is 14.7 psi or 33.95 feet of pure water, hence when water is put under a complete vacuum it will rise about 34 feet: 14.7psi/.433psi per foot = 33.95);
b. The solid stress is directional, and it is exerted on the rock frame, but may transmit itself to the fluid phase also, when the fluid cannot escape or relieve the pressure. Consequently, fluids in the earth may exhibit a pressure greater than that from a static column of fluid, and this may be:
S = density, ρ (Greek Rho or r), x gravitational constant g x height, or S.G. (specific gravity of rock, which is that density relative to water, as a ratio) x pounds/volume of water x height, or

S = S.G.(rock) x .433 psi./foot(water) x height of column of rock.
In the literature, you may see stress symbolized by σ (Greek sigma or s).

This last relation shows the stress exerted along the rock frame, which is transmitted to the fluid for the abnormal case. This again is a static stress, and is not the maximum stress which may be exerted on rock (the static overburden on rock is about 1 psi/foot thickness in sedimentary rock). Rock may temporarily exhibit stresses which are unstable, which are very large- sufficient to cause failure (earthquakes, sliding, or other movement). S.G. of rock is determined by its density, ρ = 2.65 for quartz x S.G of.433 for water = 1.15; clays are lighter:

S.G.(rock) = ρ(rock)/ρ(water) = density of rock(physics cgs or cm, gram, second units-
grams/cubic centimeter)/1.0, approximately.

An abnormally large rock stress usually results locally in faulting or slumping and creep, but if unrelieved completely may be observed directionally along fractures (jointing as indicated by geological terminology). It is usually very difficult or impossible to determine the original magnitude or rate of relief of stress, but the orientation easily may be seen in fractures or fault movement. A clue to regional stress on rock is noted by parallel fracture lines in flat rock, and these may occur consistently over hundreds of kilometers.
c. The stable column of rock may contain two stress indications:
i. the pressure on the fluid phase
P = S.G. of water x .433psi/ft x height;
whereas the rock stress:
ii. S = S.G. of rock x .433 x height of rock, psi. S.G. of rock is at least 2.5 (gypsum is an exception, with 2.3) and normally S is approximately 1.0 psi/ft. At 10,000 feet, normal water head is 4330 psi, whereas it may be confined in rock with normal overburden at 10,000 psi. But
iii. S > greater than S(static rock) may accompany water at normal hydraulic head, whenever there is an active solid stress such as in volcanic areas (with water unconfined). The > symbol connotes greater than, with < meaning less than.
Hot Springs near Tofino, Vancouver Island, Canada exit on a peninsula near the Pacific Ocean

This all sounds strange, but consider your auto windshield- which may have free-flowing water rolling down its flat surface, while the solid glass is under extreme stress from its curved configuration.
Now consider these other rare occurrences:
1. A lens of sediment, surrounded by impermeable shale or clay, contains water with no possibility of quick escape. Whenever this lens is squeezed by the overburden or other force- either lateral or vertical- the water will carry the total stress of the confinement, which may be about 1 psi/foot (double the normal hydraulic head expected). This yields a blowout in an open or water-filled drill hole, whenever the lens is drilled (since the water now has an exit- right into the borehole). Oil Drillers are aware of this case, and it is overcome by putting high density materials in the drilling mud.
2. An isolated lens of rock may have sufficiently high temperature, such that Methane or CO2 gas is being generated faster than it can exit the lens. This is a fairly normal case in the deep earth, (greater than 5 kilometers depth), since there is high temperature everywhere. This is abnormally-high pressure, named Geopressure. Even in intrusive rock, such as granite, there is sufficient bacterial and organic activity to generate gas release. An interesting case occurring at this writing is located in East Java (near Surabaya), where a driller for oil encountered high pressured hot shale which has been flowing over several square miles for many months without stopping. The mud has flooded many houses.
3. The strangest case, which I have investigated- publishing a professional paper about it- is that of under-pressure. This occurs whenever there is CO2 baked out of deep limestone- by a hot intrusion- which remains in the gaseous phase, and when the gas percolating upward encounters fresh water not saturated in the carbon-dioxide. In this case, the gas quickly dissolves in the fresh shallow water and the volume of gas plus water shrinks- reducing the pressure when the permeability is abnormally low. For the Rocky Mountain area, this is not too rare, and the borehole fluid may be sucked into the permeable zones containing under-pressured fluid (P< .433psi/ft x depth). Pressure at 10,000 feet depth is less than 4330 psi, for this case.
4. Even in normally-pressured areas, where the water table is deep (as near the Grand Canyon), the pressure at the bottom of a drilled hole will be much less than .433 psi/foot x depth, since most of the borehole is filled with air or light weight fluid. In this case,
P= .433 psi/foot x height of water in the well bore, from water table to bottom hole. This is normal pressure with abnormal depth of water, since the water has drained out into the canyon. This will occur on mountains also where the water has percolated toward springs near the base of the terrain. In the western USA, it is common in the desert for the water table to occur many feet below the ground surface, where water pressure is normal wherever it is found. Only in abnormally hot or stressed rock will there be abnormal water pressure. The stress may derive from tectonics, from movement along faulting, and from generation of gas from organics abnormally heated.
Summing all of this, the pressure of the fluid in the Crust is unknown until it is measured. It can be estimated from gradients measured in nearby wells, or taken to be the normal pressure dependent upon the depth where it is found, but it is never known precisely until it is measured. The main reason for this uncertainty is that the Earth stress generating the pressure other than normal is unknown and cannot be determined in advance. This further illustrates the dilemma for Geologists, that since they never know with certainty what lies below their feet, they cannot know what the stresses will be there either.
How one can overcome this dilemma is to make regional maps and isolate the areas which are anomalous in some property which can be determined in advance- for example, gravity, temperature, acoustics, or spontaneous potentials (resulting in terrestrial, sometimes named Telluric, currents) in the earth. Anomalous geological, geothermal, or geochemical areas can be expected to exhibit anomalous stresses and pressures.

Location of Anomalous areas, by use of Geochemical Maps

I have mapped properties obtained from well logs and springs over regions as large as a county. The physical parameters which may be found from well log libraries and water chemistry may be plotted on a map- regardless of the uncertainty of depth of origin. These include;
1. Spring and wellbore temperatures;
2. Spring and well logged water salinity concentrations, TDS or total dissolved solids:
3. Formation Resistivities and Spontaneous Potentials (SP);
4. Radioactivity Magnitudes and individual elements’ gamma ray magnitudes;
5. Temperature Gradients, or temperature change from ground surface to bottom hole depths, Gt = Tbh –Tsurf/Depth, in hundreds of feet (This number will generally be 1.0 degrees/hundred feet, F change/hft or larger). This is better than using T alone, since temperature regularly increases with depth in the earth, and gradients can be compared from well to well. However, springs temperatures have no depth and must be used directly. The temperature of springs does vary with elevation in the mountains, and with latitude, so that one must compare T with others in a given latitude and elevation. A graph may be made at any latitude, showing the variation with elevation, and an extrapolation for the elevation of interest is simple. The normal temperature is near the annual mean temperature of the shallow subsurface (100 feet deep);
6. Concentration of any ion of interest must be normalized for evaporation or concentration caused by handling- the most trusted anion is Cl¯ , which does not interact with other ions or solids significantly (Cl ion has a half life of millions of years), and it is used in the following way:

K(normalized) = K+/Cl¯, using similar units for both ions; and,

7. Soundings of resistivity variation with depth, to locate Water Tables (lowest resistivity) or Rock with unusually high resistivity.

When a map is made on any one of the above parameters, any anomalous magnitude will stand out- showing that it is significantly different than the trend. This allows it to be inspected on its own merits, so that it may be confirmed as being anomalous. An example is that for SP, which varies with water salinity, water movement (Electro-kinetic Potential), and chemical oxidation-reduction (Redox) reactions. A map made on this parameter, countywide, will show sudden changes, which indicate either moving water, unusual chemical activity (such as reactions involving Uranium, Sulfur, or noxious gases), or strong brines (which are associated with oil, evaporites, or salt domes). Other means must be used to determine which of several possibilities are involved, but the anomaly is definitely located using this process.

Mammoth lake, CA has many indications of active movement of the Crust, including Steam, Water, Vulcanism, and Fissures

Thursday, December 13, 2007

ShalElog- an Electric Log for Wellbores

ShalElog- a Geochemical Log, made from cuttings retrieved from well drilling
Information is vital, when drilling a well for water, for hydrocarbons, or for steam. Not only should the one investing in an expensive borehole (twenty dollars or more per foot) have an estimate of the risks of failure or success, but he should have an accurate appraisal of the earth penetrated (in terms of encountered rock and fluids). He may find the fluid is obscure, even when it is present.
Water wells are usually drilled by individuals interested in finding water as shallow and as inexpensive as possible, on their properties. After all, water should be cheap, since it seems to be available wherever there is life. However, in the desert water is more elusive- for the quantity man needs, the amount found may prove to be skimpy.
The water table in desert areas (below which water saturates the rock) may be thousands of feet deep. People living near the Grand Canyon find that the gash in the earth has allowed water to percolate (drain down) into the canyon at 5000 feet depth or more. This fact makes domestic water in The Strip very dear. These expensive wells require as much information as possible from drilling, since the total cost is large, and the information found from drilling may incur only a small part of the total cost.
Landowners are reluctant to ask commercial well loggers to log shallow wells (measure rock properties continually from near the top to the bottom of the hole), since it may double the cost of the well to do so. However, they can get a log from the cuttings brought to the surface by the driller. This represents free information, providing it is analyzed or measured later.
Shale cuttings, made into a ShalElog
(patented shale Electric Log)

provide one method of analyzing the rock penetrated while drilling the hole. This may be valuable whenever the hole appears to be dry (there is no readily available fluid in it), and the owner has to decide on abandoning the hole.
The driller should wash and bag cuttings each 10 feet from the well, for use in evaluating the well whenever fluid is not found (this can be done if requested in advance, at no extra cost). These cuttings will keep indefinitely, and if they have been washed and dried they will not be contaminated when stored. The fine material, such as clay, silt, and fine sand stores both organic and inorganic chemicals and these may be measured later should the rock penetrated not be understood. Low Conductivity water (low salt content, with high Resistivity) can be found in zones with thick sands, suitable for drinking, using this log.
These chemicals may be flushed from the cuttings by means of making a mud or slurry from them. This is done by dis-aggregating the dried and heated (in a kitchen skillet) slivers of rock with a mortar and pestle (or stirring dish and mashing tool- not grinding), so that they appear to be clay-like. These then can be mixed with equal weights of distilled water to make a mud or slurry, which can be measured for several properties:

a. Electrical resistivity, R, or recipocally the conductivity of the mud, in ohm-meters or mho/centimeters (Mho is the inverse of Ohm- but not the WHO!);
b. The rate of fluid flow from the slurry, by means of a filter press, in minutes per cubic centimeter. This may vary from one to ten minutes per cubic centimeter, min/cc;
c. The color of the filtered fluid, called effluent, which can easily be graded into clear, slightly yellow, yellow, amber, and gold or brown visual colors;
d. Resistivity of the effluent or filtrate, ohm-meters;
e. Contents of the filtrate, Cion (ionic concentration) , such as Na+, K+, Ca++, or other dissolved chemicals, using an ion-sensitive membrane (measured in electrical millivolts); and
f. Trace elements, such as Boron or other constituent of interest. All of these operations may be made in ten minutes, to keep up with the driller collecting the drilled samples, and a record (Graph presentation) later can be made to present these data- which is called a Log.
Other parameters or calculated terms may be found from the above data, which can be used to evaluate the rock and fluids encountered. These include a factor F= Rmud/Rfluid, where R is resistivity, which is sensitive to the solids found in the cuttings (e.g. limey solids compared to silt). Some of these terms are shown in the following ShalElog, which was made in Turkey by me.

The Presentation of ShalElog is similar to Electric logs made for drilled wells
The left-hand curve, which presents the Na+ content (read left-ward), is a measure of the saltiness of the fluid. In oil wells, this saltiness increases with depth, and is particularly interesting around oil deposits, since the salt water and black oil seem to have an affinity for each other. It is somewhat similar to the SP log, which is conventionally made for oil wells, but the contents pertain to shales or fine sediments, and this is not necessarily the same as with sandstones which contain both salt water and oil (sometimes).
Potassium, K+, is an interesting ion, and it is not common in subsurface waters in large amounts. It is normally some one-twentieth to one-tenth of the concentration of Na+. I have found that it is present more so whenever an active fault or fracture allows fluid to rise vertically from a hotter zone in the earth. This occurs because of its small ionic size, its relatively small hydration with water (recall that physicians prescribe it in lieu of sodium for heart patients, who take on water with ordinary salt), and its increased solubility with higher temperatures. Generally, geologists do not agree that it indicates anything abnormal, so you may want to get other opinions. But I have mapped this ion on county-wide maps, and found that it occurs in linear map presentations in springs, in subsurface wells, and whenever there is abnormal temperature. It travels much more easily when the fluid is warmed, compared to Na+, and consequently may be mapped or measured in boreholes for anomalous geological circumstances. It is known to derive from weathered potash feldspars, shales with illite in them, and from granites. It may be more common whenever evaporites such as playa lakes occur, since it is more soluble than most other salts and occurs whenever the lakes completely dry (as in the desert).

Notice that K+ is highest on the Thrace log, near an amber filtrate, and that it generally increases with depth (temperature).

ShalElog in Geothermal Logs indicates abnormal K+ and anomalous Geology
Notice that K+ (following Photo) is plotted occasionally on the geothermal log shown below, and it indicates abnormal temperature or open fracturing or faulting. Again, it generally increases with depth in this hot hole in an area which produces steam and has fumaroles at the ground surface. In this case there is also an anomaly near the surface (60- 70 meters), and there is steam emission from the nearby area. Again, K+ is a small ion, which has small hydration, compared to Na+, consequently it moves easily through small fractures found at faulting or which are over-pressured.

Geothermal Well Logs shows wide Variations of Dissolved Ions
Sodium Ion variation in the Earth
Sodium ion is the most common ion in groundwater and in seawater, the reason being that it is a result of the dissolution of feldspars and hornblende- the most common soluble minerals in igneous rocks. It is also a result of HCl acid from volcanoes reacting with alkali rocks to produce a salt plus water:

HCl + Na Rocks > H20 + NaCl + anions or other minerals

For limestone areas, Ca++ and Mg++ will predominate in near-surface waters, but again the Na+ ion will increase in importance with depth and temperature, until it is dominant.
This is shown in the Thrace log, but not in the geothermal case, since K+ has supplanted Na+. Sodium and Potassium ions seem to compete, similarly as they do in the human body. Living cells generally contain K+ =10x the Na+ inside, compared with the free fluid outside having 1/10x the Na+. This is mentioned because shales act as membranes in the earth, which cause an ionic concentration contrast across their boundary- similarly to the cell wall. I conjecture that Life is involved with this chemical change, at least in taking advantage of it- notice that the highest K+ in the geothermal well occurs near the bubbling cuttings emissions.
A Model is shown below, which indicates depths where the various waters occur in Large Basins; this indicates that there are four types of Water- somewhat stratified in the Crust, according to temperature and compaction of the Rocks (Permeability or ease of water movement):
1. Meteoric Water, which is potable or drink-able;
2. Ionized Water, which may be too salty to drink;
3. Chemically-Reduced Water, containing stinking compounds; and,
4. Acid Water, which has a pH less than 7.0, depending upon abnormal temperature.

Model for a Large Basin, for vertical distribution of Water Types

Tuesday, December 11, 2007

Happy Holidays!

The “Rights” of the Holiday Season
Aside from the necessity of conforming to the institutions arranged throughout Time by charismatic (and Epiphanatic) Leaders, what does the Earth Scientist have to offer, to determine the Truth of Man’s relation to his world- at the termination of another Solar Year? Nowadays, science has determined that Man is just a part of the World- not the master of it. He does seem to have the ability to disrupt the orderly progression of the Earth’s Evolution, but does he have the Wisdom and Knowledge to allow the tremendous expansion of Population and the Use of the Earth’s Crust to “jive’? Man does have the numbers and the ability to reason and organize the population to exploit the Crust of the Earth for his selfish benefit, but does he have the foresight to exercise restraint in his Exploitation?
When as a graduate student at Texas A&M, I remember the professor asking the class to concentrate on how to conserve oil and gas resources. The accentuation was on ways to produce the resources without waste- not bypassing large amounts of oil in the haste to make use of it. This would involve ways to use secondary recovery to bring more oil to the surface economically, but more importantly not to “waste” it by leaving pockets of oil in the earth. At that tender age of 29, I inquired whether it was not more wasteful to burn the oil (as auto engine gasoline) - rather than to use it for petrochemicals. That it would be less wasteful to leave the energy and chemicals in the earth, than to burn them- where they are gone forever, leaving ash and waste products instead. In those days, Saudi Arabia was flaring off all of the gas produced with the oil, since it was too much trouble to fiddle with the less profitable gas cap. And there was actually too much production of oil possible- so that the Railroad Commission of Texas restricted production to 10 days or so monthly. Of course, the world population has doubled since the 50’s, and everyone is entitled to his own auto- if he can muster the wealth to invest in and maintain it.
Although there has been a sea change in the attitudes towards our interaction with the Earth and its Resources- what with the population becoming excessive- nevertheless, all still want their personal autos and the garaging and land space to accommodate all of this. People in the cities are arrayed against those in open spaces of the world, in idealizing a view of the earth (its cosmetic and natural appearance) rather than the economical use of it.
How then can people working in the various Earth Sciences accommodate their source of income via employers (which is to exploit the Earth and its resources), with the desire of the thinkers to allow the Earth to proceed on its natural course- where most processes occur with gradual and small changes, instead of at large rates as determined by the desire for immediate returns on investment? Haven’t there always been Jeremiahs who prophesy doom as the results of man’s material activities?
How about myself, who has spent most of his professional career in developing techniques which are faster, less expensive, and novel to find and develop natural resources such as fluids in the earth? Working almost alone, I found techniques which would locate subsurface water in the desert, and sense gas from chemical changes according to pressure and chemical change in cuttings measurements from wellbores. Wasn’t the end result of all this just to encourage more people to turn to the desert or to waste areas where there were not sufficient resources previously?

A Log may be made in a shallow well, from Surface Cuttings thrown out on the Ground
“Man is known by his Rubbish Pile” is one assessment fondly made by Archeologists, where middens yield knowledge of what Man did in the past. Is this to be the legacy of our generation- packrats leaving artifacts saved by virtue of coating their possessions with urine, for the delight of the archeologists? What we exhibited were analyze-able piles of trash, including that in the atmosphere and in our waters?
Evidently, Life has always adjusted its environment to accommodate its desired goals- to propagate itself and to decrease the Entropy of the Universe. The great engineer- the Beaver- has long ago upstaged Man in re-arranging his streams to make lakes which reduce erosion, save resources, and allow for his progeny and other life forms to take advantage of his activities.
Now we find hints that early Life has done the same- rearranged its environment, for the benefit of its successors. As deep as we drill, we find that there is Life, in the form of bacteria which eat on the crust. Since the Proterozoic, this has reduced the crust to that of a habitat, gradually changing the mainly basalts of the early days to that of granite (after re-melting) which is re-cycled again and again through subduction to increase in mass with time (Life takes out what it desires and leaves increasing silicates as the heavy minerals and ions are concentrated in fine sediments). It appears that the crust has become thicker with time since the 3 billion ybp eon.
Regardless of Man’s desire to increase his material possessions, there is a great need to understand the Earth - which is Man’s only domain so far. Man’s leaders can choose to accommodate both of these pursuits, by encouraging an interaction with the Earth just sufficiently to meet the material needs (minimizing his “wants”, while accentuating interest in earth processes). Evidently some primitive cultures did similarly, developing astronomy or other observations of natural events which stimulated the population to develop understanding- rather than just for the accumulation of excessive material wealth.

Christmas as a Time of Reflection

“It’s Unnatural”, the Observer stated- “this scurrying about to transfer the results of my Labor to Purchase material goods for Satisfaction of my Emotions”

All have felt it- the feeling of Charity and Communion, which is suddenly thrust upon the crowd during the end of the year season. People are racing to and fro to accumulate presents for their companions (not necessarily their “loved ones”). And it is not really an expression of trade of gifts for expectations of return. I believe that they genuinely have compassion and a desire to instill good will. The normally selfish person contributes “something for the Pot”. This charitable effort is laudable, but don’t expect it to continue post-Christmas, since selfishness and rationality will again prevail, once the period of goodwill has expired.

Capture the Time Now, while our Emotions allow
Us to embrace our better selves temporarily;
Yield to the Group, while rejecting the coop
Of our rational and advantaged side, summarily.

Question for the day- rationality to allay-
Is whether this decile is Characteristic?
Are we to believe, that there’s no reprieve
For the other nine-tenths- opportunistic?

Even the Muse’s Rhyme, for most of the Time
Cannot easily be brought to the Fore;
Hence we’re stuck with the Fact that the majority Act
Hinges on the dominant Desire at our Core.

Merchants are Adroit, and quick to Exploit
This Coming-out- of-ourselves almost annually.
So manage yourself, using some of your Stealth
For your Spirit to channel positives most Manually.

Harold L. Overton

Monday, December 10, 2007

Rock Canyon, AZ (Arizona Strip)

The Canyon Entrance is simpler at Rock Canyon- Flexure-Created Intersecting Fractures?

One Way of finding how the Hurricane fault Hf, originates is to look at canyons which cut it, so that it may be viewed in three dimensions.
We have found that the Laverkin Quarry introduces a double anomaly- there is the Hf in several splays (parallel presentations), simultaneously showing interference with Hf by grabens, slickensides, and beds dipping down in two different directions- to the west and to the north. This is an additional geological anomaly, since mostly the stratigraphy dips up to the west for local manifestations of Hf. This feature is near Pleistocene vulcanism, which might help explain the additional anomaly, but more likely both vulcanism and Hf are caused by the same phenomenon. The basalt ascends the near-vertical fractures opened by whatever pushes up the highlands to the east. It is instructive to look at canyons which represent the normal Hf- without the added complexity of the second anomaly (it is difficult to climb Hf for most of its scarp, but at Laverkin one may drive up the scarp face because of the gradually sloping multi-faulted terrain & switchbacks which allow road-building to the Colorado Plateau, CP above). We have several simple canyons cutting Hf nearby, and Rock Canyon is one just south of the AZ border. We will assume that it is more easily understood. This canyon may be approached most easily from Hurricane town, taking the airport road south, crossing the border of AZ, and proceeding south another two miles (avoiding roads to the right which connect with roads from St. George), and turning west then south again where the obvious arroyo crossing is reached. This same unmarked road eventually connects with Black Rock Canyon road- a deteriorating road towards Mount Trumbull along the Hurricane Cliffs.

Rock Canyon
(700 W from Hurricane, UT, south to AZ, just past border, four miles past the diagonal road in UT- west to connect with BLM 59), S1, 2, 11, and 12 T41N R10W, AZ:
Rock canyon
is a tributary of Fort Pierce Creek, and becomes Short Creek on the rim to the east above.
This canyon has Paleozoic Kaibab limestone, Pk, at the top and Toroweep, Pt, lower in elevation at the Hurricane cliffs. The dip of Pk is up to the west, at the present cliffs, but the red beds far to the west dip down to the west. Hike from the intersection of gravel road and arroyo, cross-country toward the canyon mouth- about one mile east.

The Kaibab and Toroweap Formations, occurring in the Grand Canyon, or upper Permian (Paleozoic) loom ahead of the canyon opening

The contact of Paleozoic vs. Mesozoic near Hf is covered with rubble over a 1/2 km zone E-W, so that the original fault plane cannot be seen. In this interval, some petrified wood can be spotted, so that one is certain that Mesozoic debris is at the ground surface, west of present cliffs.
Some small normal faults, falling down to the west, can be measured in the north wall of the canyon at the mouth in Pt or the underlying Queantoweap, Pq, with no more than 2 meters displacement.

Several small Normal Faults are easily measured at the Entrance of Rock Canyon

The fault planes are essentially vertical in all cases, parallel to N-S fracture surfaces in the creek bottom. Incidentally, N-S fractures in the creek bed cut older NW-SE oriented fractures and those at other angles, displaying horizontal displacement (shearing) of the older fractures. This demonstrates that the N-S shearing is younger, as would be expected for the N-S oriented Hurricane fault (and that some shear component is present, for the dominant normal faulting).
The conglomerates in the canyon walls appear to be young Pleistocene, Plc. The cementation is weak, and the boulders are mostly limestone. This Plc occurs in cross canyons west of the main cliffs, indicating very young N-S faults and associated washes.
Hike with Ben Everitt and Don Scholten, 12/5/07, eastward from the main gravel-Black Rock Canyon Road to the Rock Canyon Mouth:
Again, the fault trace is obscured by an outwash plain and alluvial fans, but splays on the east side of the main Hf can be measured as small displacement normal faults in the Pt or underlying Queantoweap, Pq (equivalent to Permian redbeds, or Supai).
Photo of Normal fault- buildup to Hf to the east

The North to South fractures and small faulting occur in a narrow band at the entrance to the canyon, but the main fault cannot be seen

Abrupt Terminations of westward-oriented outwash deposits may be seen in several outcrops to the north and south of the canyon, hinting that the youngest Hf is well west of the canyon mouth (but is obscured, except in one small outcrop of Pq at an abrupt outwash cutoff to the north). The 4 outwash terminations north and south of Rock Canyon do not align, and this can be expected if there is a discontinuity in the trend of Hf at the present scarp- canyon mouth. There seems to be a slight hinge across the Hf canyon, and this may have been the impetus for allowing Short Creek to exit at this weakness. An outstanding question concerning this feature is the presence of a few streams crossing Hf against the present topography (including this one- cutting through a hill), allowing creeks to exit across the Hf scarp when it dips up to the west. This present rise constitutes a barrier to stream flow, unless the water proceeded subsurface until it emerged as springs- which gradually increased in flow until a canyon was developed above them.
The hinge in the subsurface, allowing a flexure for fracture development, is rare near Ηf, and it has been investigated at the following locations: Laverkin quarry, Virgin River mouth, and Ash Creek. It is suspected that the exit of streams is dependent upon this geological anomaly- that hinges create subsurface fracture systems and this allows underground water to exit CP, when otherwise it would be blocked by a topographical barrier. With time, this subsurface flow creates channels (caves) and eventually creates canyons through the barrier. Laverkin quarry is the most prominent of these anomalies, while Rock Canyon is next- allowing the Short Creek to exit (but in a younger period of development).What needs to be confirmed is whether the NW-SE fracture systems were most necessary for this stream orientation (since the N-S fractures and their orthogonals do not show up in stream patterns (except for Rock Canyon). The Virgin River seems to follow NW-SE orientations and their orthogonals, allowing the river trace to zig-zag across the CP. Recall that I am testing the projection that the N-S fractures are younger than the NW-SE ones, and that they would have dominated drainage in the times since 2 mybp (Pleistocene).
The next projection is that these geological anomalies or weaknesses are accompanied by vulcanism- which allowed Mantle basalt to exit through the new fractures systems N-S and its orthogonal E-W weaknesses. This has happened near the Laverkin Quarry and the Ash Creek- Toquerville locations. This happens also at the Honeymoon Canyon, but it is not apparent at Rock Creek- which is a larger canyon carrying more water than Honeymoon. There is a vent SW 4 miles distant from the Rock Canyon mouth, but this seems too far for the magma to have been influenced by the suspected hinge. That Rock Canyon was created by a hinge is reinforced by the fact that Short Creek runs E-W, which would be on an orthogonal (perpendicular) to Hf fracturing.
We will proceed in this investigation, trying to determine whether:
1. Hf is initiated by a new stress system, which orients N-S, superseding the older NW-SE fracture system noticed over western outcrops from the CP into the B&R;
2. The new N-S system would be a normal faulting- dominated one, as contrasted with the older NW-SE shear stresses (from Pre-Pleistocene times);
3. Accompanying this new extensional system of normal faults would be vulcanism coming all the way from the Mantle. This would happen if the system is being initiated by equatorial bulge shrinkage, as the Earth slows (reducing the centrifugal force creating the initial bulge); and
4. A complication to all this conjecture about global shrinking is that of the type of stresses created by the reduction of centrifugal force as the Earth slows. The first result should be that of compression vertically, as the Crust shrinks vertically. Blocks of crust should move downward, as centrifugal force is replaced by gravitational attraction, and the relative movement would be determined by isostatic adjustment. Should blocks of crust be out of equilibrium with regional stresses (due to heating, subduction, erosion-rebound, or other slow stress-changing processes) this instability could be corrected simultaneously with the crustal shrinking. This would be similar to slinging a vial of mercury side-by-side with one of lower weight plastic hot rock altogether in a circular movement at the end of a string. As the circular swinging motion is reduced, the mercury would tend to drop back toward the center of swinging more than the lesser density rock. This would result in vertical shear between the two different materials, showing up as a normal fault. In a pure sense, there should be no lateral shear, but local density changes due to variations of stratigraphy could create shear. These effects should be minor and local- not regional.
This hike illustrates Hf for its simpler presentation, and no conclusions will be reached as to its incipience. Flexure of the crust, vulcanism correlation, updip-to-west stratigraphy, and broaching of Hf scarp by streams will be further cataloged.

Monday, December 3, 2007

Find out What's happening to the Ground Surface below your feet in Washington County, UT

A Pleistocene Volcano, named Crater Hill, is one that has "Popped Up" within the last one-third million years

The Ground is moving near Hurricane, Utah!

The surface of the Earth is moving noticeably in Washington County, and if one hikes regularly on the trails, it is detectable.
Upon arriving in the towns of Hurricane and St. George, the remaining basalt flows from ancient volcanoes are the first visible clues that geological processes have happened fairly recently. Several of these flows are in populated areas, and form the barriers to traffic across the towns. These basalt-capped mesas have had molten rock flow similarly to streams over the surface of the ground in old creek beds, in times less than one million years ago (sometimes, at times only 100,000 years past). These mesas are now covered with rock that is very resistant to erosion (black basalt), and the paths of the stream beds which they occupied in ancient time can now be followed to determine the direction of flowing creeks in that long-ago period. Looking on a map for these mesas, it is apparent that creeks moved mainly southward from the 21 million year Pine Valley Mountains PVM- which is the direction of the trend of the old basalt-covered mesas. Nowadays, the streams have carried away the soft surrounding sandstones, so that new streams move in other directions- sometimes similarly to the Virgin, which moves southwest or west in Hurricane. So, erosion is a prime factor in determining the movement of the Earth’s Crust in Washington County. But there are other independent movements, which may be subtle, but are important in understanding what’s happening in this rapidly-changing region, Geologically. These are listed below, so that one can focus on them while hiking the region:
1. The Colorado Plateau, CP, is uplifting east of Hurricane, relative to the Basin and Range, B&R, to the west, and this may be sub-divided into several components:
a. The Plateau is uplifting far from the Hurricane fault, and this can be seen with the following link: This shows a small upward movement, on the order of a centimeter, for the period of a few years of measurement. This may be due to the loss of mass removed by the Virgin and Colorado rivers, as sediment is carried away annually, and to the resulting reduction of weight pushing downward. This is called Rebound.
b. The CP is heated by several processes taking place now, and these result in thermal expansion upward (similar to an iron bar which expands when heated in a fire). This can be noticed when drilling wells, which are measured for abnormal bottom-hole temperatures. The usual suspects rounded up for explanation for this present heating include radioactive decay, heat given off by increase of density with forced deep burial of rock (similar to the heating of air in your tires, whenever you increase the pressure), and friction of one rock surface sliding over another.
c. Finally, there are places in CP which move much faster than others nearby, and these are under investigation. An example is the rising mountainous area east of Cedar City. It appears that the north-trending Hurricane fault is acting like the blades of scissors which move increasingly upward to the point of the scissors as one looks north of Laverkin.

2. The ground surface near previously hot volcanism reacts as the underground rock cools- reverse to that of thermal expansion- and the land above the volume with greatest cooling sinks. This is noticeable along the Hurricane fault, Hf, so that when the maximum cooling occurs at the fault exposure, there is tilting as the land above the cooling magma chamber sinks the most at the open fault surface, Hf. The western edge of the sinking mass remains relatively high in the form of a sharp edge of rock, known as a Hogback (since this mass incurred less heating in the first place). In this case there is not only vertical shrinking but also tilting locally- as much as one mile distant from the volcanic cone or plug (example: the Laverkin Hogback near the confluence park north of Virgin River).

Laverkin Hogback is Photographed between the two Hurricane Craters which helped create it
3. The Earth is shrinking as it slows, particularly at regions where an equatorial bulge developed in early days when the spin of the Earth was greater (days were shorter). This happens for the earth’s crust where the bulge is more noticeable- in the latitudes less than 45 degrees, This should be a continuing shrinkage and is thought to develop north to south, N-S, fractures in the crust. Accompanying these are perpendicular cracks, or those at 90 degrees, E-W, to the principal N-S ones (example: the N-S Hurricane fault).
4. Whenever masses of the earth’s crust collide with each other, particularly at small angles to each other, shear develops as the separate rock masses slide past. This causes shear laterally, of the rock masses, and this is noticed to occur mainly along northwest to southeast, NW-SE, orientations (and orthogonals- perpendicular- to these). Consequently, faulting occurs at 8 divisions of the circle of directions, or of the 360 degree compass rose- N-S, NE-SW, E-W, and NW-SE- 45 degrees apart. The diagonal directions should exhibit shear, while the others should exhibit normal faulting or simple downdrop. Normal faulting is by far the most common, while shear in the diagonal directions is the most difficult to observe- since it moves laterally along the earth’s surface with little noticeable displacement of geological formations vertically (example: the line of Wet Sandy and Santa Clara Creeks eroded into Pine Valley Mountains, PVM).
5. Finally, the earth reacts at irregular intervals, as adjustments to all of the above movements occur. This produces earthquakes, and these accompanying slipping at depth- above which is a place on the ground called the epicenter- in addition to violent movements at the earth’s surface. These locations tend to be found on lines of stress direction, frequently NW-SE orientations- called linears or lineaments, or open cracks in the ground surface. Springs and gases may issue along these linears, and chemical changes may be noticed at the surface of the ground (example: Pah Tempe hot spring and H²S gas near Sullivan’s Knoll).

Follow the sequences outlined above, so that you can see the result of movements occurring in the earth where you hike. This Washington County, Utah area has almost all types of Earth processes and movements known to Earth Scientists. Watching for these movements can help you in determining what to expect in the future for your Real Estate, your landscape, and your hiking trail.

Thursday, November 29, 2007

Comparison of Hurricane (City) Fault Canyons with that at Laverkin Quarry

Canyon Orientation is controlled by N-S Fracturing and Faulting in parts of the path

Comparison of Hf Scarp canyons to Laverkin Quarry Anomaly

One way of determining the anomalous character of the canyons leading eastward from Laverkin town is to compare them with other locations on the Hurricane fault, where there is only a simple erosional canyon (or wash). Almost all of Hf scarp consists of a massive wall, except near Laverkin, showing the upthrown older sedimentary rocks to the east, with the younger downthrown column buried beneath your feet. Only a wash leading from the Colorado Plateau to the east allows inspection of the rock, and normally there is no access by road or a simple ramp. Hiway 9 towards Zion NP is one of the rare exceptions, where switchbacks allow driving to the CP above.
Two of the canyons leading into CP are located within the town of Hurricane. Hikers may enter via Gould’s Wash (a significant drainage) and at the town airport- named Frog Hollow, a normally dry wash of only ½ km length. Access of these may be made via 700 West in Hurricane, where a left turn is made at 400 South to 160 East. Park at 400 S, since there is no parking on 160 E, for Gould’s Wash. To access the minor airport canyon, continue on 700 W to the 2300 South road at the airport entrance, turning left instead into a new housing area, and then right onto the last paved street. The Canyon mouth may be seen from the road, and the end of the pavement allows parking to walk the short distance to the canyon mouth.

Gould's Wash passes diagonally through Hurricane to empty into the Virgin River
Frog Hollow (below)exits at the local Airport, and rarely flows

Gould's Wash passes diagonally through Hurricane to empty into the Virgin River

Anomalous Behavior of Hf at Laverkin
Normally, Hf scarp dips up to the west- which prevents drainage from the east, but in both of the Hurricane canyons, slumping and faulting has occurred allowing flow during the rainy season. Hiking into the canyons over 200 meters shows that the rim has been disturbed by fractures and faulting- which allowed the drainage to capture the weaknesses of the rock and exit. This is not normally the case, and only a few streams or washes exit CP for the 50 km of scarp investigated.
Since slumping and faulting also have caused the anomaly at Laverkin Quarry, what is different about these Hurricane canyons to maintain the sharp scarp, and to prevent large erosion of the canyon mouth? Geologists mapping the stratigraphy would answer this simply, by saying that there are parallel faults for the quarry, while the stratigraphic change is entirely in competent limestone for the canyon mouths. This is insufficient for an understanding however, since something deep in the crust has created the multiple faulting- allowing the Mesozoic to slump down to the west for the quarry location. Furthermore, since there are indications from slickensides that there was lateral faulting, something is wrenching the CP at the quarry, but not at the limestone canyons. I have proposed that there is rotation of the CP at the quarry, and this is shown on both sides of a graben there- both sides showing that CP moved counter-clockwise relative to the Basin and Range, B&R.

Large active (unfilled by soil) Fissures exist on the north side of the Virgin, but not the south

After hiking in both canyons a few hundred meters, N-S fractures can be readily seen to have influenced the drainage from the east. Since the CP is to the east, this means that orthogonal (right-angle to the main openings) fractures are accessed also, for the drainage to proceed. This is easily seen for the Virgin River exiting between the towns of Virgin and Laverkin. In this case, the fracture pattern has changed from NW-SE to that of N-S (as with Hf) within the last two million years, 2 mybp, and the Virgin River found these new and old openings and used them to zig-zag westward. This may be seen by looking at the Google Earth geographic map below in an earlier Blog- focusing on the river path and its sharp turns.
Still again, What’s the difference?
The Virgin River shows that there are both NW-SE and N-S fractures operating on the topography, yielding openings for the river to work westward. There is the possibility that the older NW-SE fractures have extended from the large fissures seen in the ground surface above and to the west of the Virgin all the way to the Laverkin graben and quarry.

Large open unfilled Fissures exist near the north rim of Virgin River- some Spalling

Contrary to that in the limestone near the canyons to the south, the fractures near the north side of the Virgin are wide, obviously extending, and deepening (some are 2-3 meters deep, with hardly any soil in them). Some of this can be said to be due to gravity slumping into the nearby Virgin, but others are not parallel to the river trace, but at large angles to it. Most orient towards the splay of Hf at Black Ridge to the NW, which can be seen to align with them.
Another feature of the quarry arroyos is that they seem to have been mostly abandoned, after having deposited both boulders and fine sediments separately, compared to the Hurricane canyons. This hints that the lip up to the west of the CP near the scarp is a new feature, causing the streams which once were important to be abandoned now. Should the last rise of CP noticed at Hf have happened within the last 2 million years, this would have caused the up dip-to-the-west lip of CP to cut off most flow where erosion could not keep up with the dipping up to the west of the rim. In the case of the Hurricane canyons, there is no obvious dip-up-the-west, having been replaced by slumping and faulting- allowing the young streams to more easily exit.

CP, the Colorado Plateau, is bare, compared tp the green fields of Hurricane Valley

Why do the large fissures only occur on the north side of the Virgin River? Ben Everitt has proposed that there are evaporite beds (gypsum, in addition to soft limestone) below the Kaibab, allowing the river water to dissolve out caverns as it moved deeper into the earth. One of these sinkholes caused water to drop into the river bed when the new pipeline was installed (silt-free water would penetrate fractures more easily, after a dam was installed upstream). The weakness of this case is illustrated by the fact that the sinkhole taking the water was on the south side of the river, therefore the dissolution should have been strong on that side also. It is my opinion that both widening fractures and sinkholes were present before the river reached this deep elevation, and that a geological anomaly was doing its work before the river aggravated the erosion. The Virgin at the town of Virgin has no canyon, and has to eat through a 200 meter rise to exit the CP at the town of Laverkin. This rise must have occurred as the river was eroding rapidly, and fractures allowed for quick erosion by the river water.

Again, why does the Anomaly stop at the Virgin River?

Looking to the SE, a saddle occurs in the Mesa some 5 miles away, so that the anomaly continues, but dying out as indicated by the lesser erosion in that direction. The NW-SE fractures pattern is ubiquitous over the Colorado plateau, however, and does not terminate at the boundary of CP and B&R. I believe that the newer N-S fracture system is effective dominantly near the CP edge continuing on into the B&R, and is particularly noticeable near the normal faulting occurring west of CP (for example, in extensional basins across Nevada). The locations where I have investigated this occurrence are at Verde Valley (also in the transition zone), Coal Pits stream, and at Moreno Valley on the east side of CP.

Fractures above the compass (photo below) determine erosional path of Gould's Wash

N-S faint fractures are noted to control Stream Erosion and Orientation through the Hurricane Scarp

Tuesday, November 20, 2007

Stress analysis of the regime surrounding Pine Valley Mts.PVM

PVM igneous Intrusion (Monzonite) is shown in Red, as contrasted to surrounding sedimentary Rocks

Google Earth photo shows the SE edge of PVM and its draining Wet Sandy Creek. Quail Lake is at the SW corner of the map, and Anderson Junction is near the Center (Orient onto the Occidental I-15)

There are flat and level beds almost alongside the Monzonite melt, indicating that they have not been distorted by sliding of large masses of monzonite Pine Valley Mountain Foothills, PVM, sedimentary Carmel outcrop, or by the intrusion of the hot mass

Pine Valley Mountain Foothills, PVM, sedimentary Claron outcrop

The PVM rose as a melt in Miocene times (21 mybp, million years before present, laccolith-shaped, and oriented NE-SW), and developed a mushroom-shaped overhang at about the kilometer depth in its late stages. This overhang is due to the mechanics of stress changes, as the melt rose. At approximately 1 km, the resisting stress of overburden is less than that of splitting the rock vertically, and the melt works laterally, lifting the over-lying rock (this same result has been noticed for rising Salt Domes in the Gulf Coast, USA). This is noticed in the photo shown for the Oak Grove Campground area, where the flat and level Tertiary rock is un-deformed by the rising melt, while downhill there are remnants of melt which have fallen past the weak sedimentary beds. This means that the dropped Monzonite mass has not slid over the sediments; rather it was above and to the SE of them in days when there was a lot more Mesozoic and Tertiary rock (before erosion). As the mountain and its surrounding sedimentary rock eroded in the 21 million years just past, the detached Monzonite sunk further in elevation, now displaying portions SE of the older and once deeper sedimentary rock.

Tertiary Claron (pink to white youngest limey siltstone) within 200 meters of Tm Intrusion is almost flat and level- indicating that it has not incurred monzonite sliding past it .
Study the accompanying Google Earth geographic map, to notice several things:
1. Wet Sandy Creek traces SE, to point toward Toquerville and its large Ash Creek spring;

Though SE would be the normal eroding direction for streams falling off the NE-SW oriented Pine Valley Mts, the wash east of Oak Grove trends toward the south

2. While most creeks and washes descending from PVM are somewhat irregular, Wet Sandy is fairly consistently tracing NW-SE, making a linear trend with the headwaters of Santa Clara River on the NW side of PVM;
3. Large isolated portions of Monzonite outcrop near Anderson Junction, which are seemingly anomalous; and
4. The NW-SE fracture trend is not obvious, once the Hurricane fault is intersected.
Although the trend is strongly indicated, we have no proof that this is the same NW-SE trend noticed in the Fissures near the Virgin River, or of that noticed at the Laverkin Quarry.

Re-tracing the path to the Monzonite (PVM) outcrop east of the Oak Grove campground:
Hikers in November 07 returned to the arroyo just east of the campground, to view the contact of Tertiary Claron, Tc, with the 21 mybp laccolith- seen as pink sedimentary beds within a few hundred meters of the Monzonite, Tm, sheer cliffs.
Although rubble obscures the actual contact, the continuity of Tc can be seen over one hundred meters NE-SW, to determine that Tc has not been shoved or rotated significantly (the dip of Tc into the igneous uplift is not over 5 degrees, and the formation on both sides of the arroyo is concordant). This is shown in the accompanying photos.
Also shown is a photo with an outcrop of Tm which indicates that the arroyo yielding the bare Tc has been caused by a large fracture (insufficient displacement to classify as faulting) tracing N-S into and through Tm. This was surprising, since most of the fractures in the surrounding sedimentary rock show NW-SE orientation. The N-S fractures, and faulting, are considered to be less than 2 million years of age (similar to the latest Hurricane fault expression), as contrasted to the NW-SE older set in this area. Hence the stresses causing Hf are present in this area, some 10 km distant from the fault.

Notice the Vertical Fracture which extends upward as far as can be seen- this has allowed increased erosion (forming an arroyo or wash in a N-S orientation)

Those taking this hike should remain in the arroyo until getting close enough to touch Tc, because of the thickness of manzanita and scrub oak- which is essentially impenetrable. This is a boulder-hopping hike, which requires climbing and jumping over the outhouse-sized boulders.
Re-stating the conclusions noted from a previous hike:
1. Tc was relatively unaffected by the younger intrusion of Tm, remaining fairly flat and level. This eliminates the conclusion that Tm fragments slid over Tc, moving SE downhill with time, in this area. There are segments of Tm further to the SE near Anderson Junction of I-15 which evidently did slide over the soft sediments, using them as a lubricant and carrying some Tc with the younger Tm.
2. There is possibility that Tc slid somewhat downhill, moving along the curved face (starting almost vertically, but gradually moving horizontally with time), which results in Tc dipping-down to the cliff face as the whole sedimentary column dropped (rotating due to the smaller cliff slope angle). This yields a small dip into the monzonite- less than 5 degrees for this location. Other locations to the east have a more marked dip, strongly indicating that Tc and older beds slid- taking their overlying Tm with them.

Notice the Large Dip Angle of Mesozoic beds tilting into the PVM Monzonite
Mesozoic and later Tertiary Rocks border Tm, and the elevations of each must be measured to determine which have fallen from original high positions after being lifted and penetrated by Tm
3. Underneath the pink Tc lake limestones and siltstones, there are thick and hard conglomerates, which were searched for imbrication. These showed no flow direction indication, and appear to be storm-generated- leaving pebbles and cobbles dumped into sand or silt.

Southeast of the Tc outcrop, there are blocks of Monzonite which have obviously slid down to their present position.

Linear Slickensides were found SE of the Tc outcrop in Mesozoic rock, indicating that some sliding occurred downhill of Tc

Oncoliths were found in the Mesozoic downhill of the Claron Tc

Thursday, November 15, 2007

Fracture Influence on the Virgin Diversion Pipeliine

Ben Everitt scrambles to un-scramble the slickensides along a major splay of the Hurricane fault

The Canal Trail starts on the South Rim of Virgin River, accessed via Sheep Bridge gravel road south of Virgin Town

November Hiking into Virgin Gorge via Canal Trail

Morning Shadows Create Mystery in Virgin Gorge

Google Earth Map shows Fracture pattern influence on Virgin River

Fissures and Fractures near Virgin River and Town
Access to this Trail may be made by taking the Highway toward Kanab, from Hurricane, and turnng north after reaching the top of the switchbnacks (about 1-2 miles on top of the plateau). This is an improved road going to the town Of Virgin. After 2 miles on this gravel road there will be a trail marker for the Canal Trail. Turn left and proceed on the most used dirt road, until you reach a deadend at the Virgin cliffs.
Alternately, take the Virgin hiway 9 towards Zion NP and turn south across from Mesa Road onto Sheep Bridge road (mostly dirt) for 3 miles (past the flagstone quarry). Look for the Canal Trail marker where you turn right. You can see the Virgin gtorge in the distance, and you will have to feel your way to reach it by seeing an imposing outhouse on the north skylinie.

An interesting (unplanned) experiment occurred near the Hurricane Pipeline in the late 20th century, west of the town of Virgin. This involved the Diversion dam built there to divert water for a pipeline, the Pah Tempe hot springs, fissures in the earth, and The Virgin River flow.
Previously, the 19th century-initiated Hurricane Canal had carried water through an open flume on the south bank to the agricultural area of Hurricane Valley. Because of high maintenance necessary with this canal, a pipe was laid in the canyon of the Virgin valley toward the west, superseding the old canal. There was a large amount of spalling and rock fall annually, so that it was generally known that the cliffs would continue to deteriorate. A covered pipeline would minimize this problem, and the pipe would take water from approximately the same location as the canal- some 5 km west of the town of Virgin and deliver it to farmlands in the valley to the west. This metal pipe would not only eliminate the annual maintenance, but also deliver water more efficiently along the smooth interior of the pipe.
Here is the Third Party-communicated Sequence of Events
A holding reservoir upstream of the pipe was created via a dam across the Virgin, so that water would have time to drop some of its sediment load, and so that there would be a fairly stable flow into the pipeline. The process created an unstable subsurface with the operation of large machinery and with the diversion of water into the pipeline, the Virgin River downstream of the new dam diverted its water into the earth through a sinkhole in the river bed.
Within the first few months, an increased flow of water through Pah Tempe hot springs near the Hurricane fault, Hf, occurred, consisting at first of a slug of hot water. Then the springs delivered colder water (than the original 108 degrees Fahrenheit) making the springs unattractive for public baths. The loss of water near the dam occurred in one area assumed to be a limestone sinkhole, and this was filled with rock debris and isolated with a levee. This eliminated most of the problem of diversion of water into the earth, and allowed an analysis of the plumbing system of the near subsurface (underground water flow).

My analysis of all this (not having been present during the incident) is as follows:
1. Large Fractures were present (seen now in the cliffs and ground surface to the north of the river as fissures and fractures) in the earth below the river. These previously had been partly sealed off by siltation from the muddy river and cementation from precipitation of calcite cement;

Fractures are seen in vertical views as well as horizontally on the surface North of the Virgin (Pine Valley Mountains in the background).

2. Placement of the new dam not only decreased the sediment load in the river water (fluid viscosity decreased), but aggravated the ground surface by action of heavy machinery- both of which increased the movement of water into the earth;
3. The river water moved through solution channels and fractures in the earth downhill towards the Virgin River opening in the Hurricane Cliffs;

Review this Google Map to Notice the difference between Meanders and Fracture-induced river turns (Notice the Sharp Bends, compared to rounded Meanders, seen downstream of Hf- which you may study from a previous Blog entitled "Meanders")

Descent into the Gorge has been simplified by Trail Builders

Some Fractures cross the Virgin River, showing that they are not due to gravity spalling
4. There was a reservoir of hot water available in the caves and solution channels, which was flushed out in advance of the slug of cold river water. This yielded a temporary surge of hot water through Pah Tempe springs;
5. When the cold surge behind the hot water became faster than the upward movement of hot water, the spring temperature decreased; and
6. Finally, after isolating the sinkhole, the hot springs gradually re-heated the rock and the temperature rose to approximately the original equilibrated condition.

Conclusions pertinent to the Nature of the Subsurface near the Virgin River:
A. The Virgin River has a deep canyon (approximately 200+ meters) at this location and this has created spalling cliff walls, falling parallel to the river. But this is not the reason for the large fissures orienting at angles other than those parallel to the river channel in the plateau above; they are due to the similar circumstances for the fissures and sinkholes below the river- they pre-existed the river canyon. The path of the river seems to be determined by the two sets of fractures, seen by the perpendicular sharp bends in the river;
B. These fractures orient in two principal directions- NW-SE and N-S, as measured in the plateau above and in the river paths between bends;
C. That the river has found these (new? < 1 mybp) fractures is demonstrated by the occurrence of river gravels on the plateau above (on the south side, which orient to the SW) before the ancestral Virgin was captured by the present stream flow; and
D. Fractures seen now have been aggravated by spalling of the cliffs, regardless of orientation, but they were not necessarily initiated by the canyon formation.

Enclosed below is a report following a previous hike into the Timpoweap Canyon, describing the replacement of the old canal with a steel pipeline:

Page 1
April 2007 Field Trip Report, By Ben Everitt, DGS President
The April 28 hiking field trip in Timpoweap Canyon was a great success, even if it was a little quiet out there by myself. The route is well constructed and easily followed, except for one short section that seems to exist only in the mind of the cartographer. Recent geologic mapping by Bob Biek (Hurricane Quadrangle) and Janice Hayden (Virgin Quadrangle) provide good reference to stratigraphy and surface geology. Signage explains the history of the diversions and canals built to lead water out of the canyon to the Hurricane and LaVerkin benches.
The canals are an interesting example of pioneer engineering and sheer determination in the face of difficult topography and geology. The builders made use of breccia zones and open fractures, and the easy tunneling in the gypsiferous units. Irrigators paid dearly for these shortcuts over the next century in lost water and maintenance nightmares. The canals were abandoned in 1985 and replaced with a steel pipeline.
1) Hurricane canal routed through an open fracture in the Fossil Mountain Member
This tour continues the theme that “there is no such thing as bad geology, just different kinds of interesting geology”. The canyon exposes the Timpoweap limestone and Rock Canyon members of the Moenkopi Formation, and the gypsiferous Harrisburg and cliff-forming Fossil Mountain members of the Kaibab Limestone, and the upper gypsiferous Woods Ranch member of the Toroweep Formation. There are excellent exposures of local deformation and breccias associated with paleokarst (ancient collapse due to dissolution of gypsum), and much evidence of continued collapse in recent times. Both the Harrisburg and Woods Ranch members of the Kaibab
Page 2
formation are tilted and toppling toward the river from both sides, indicating that the thick gypsums in the underlying Toroweep continue to dissolve and undermine the canyon.
2) Just below the new diversion dam, open fractures extend from the top of the Harrisburg Member into the Fossil Mountain Member, but are not yet evident in the pipeline pad.
Above the canyon rim, remnant gravels resting on the lower red member of the Moenkopi mark the course of the Virgin River before there was a Timpoweap Canyon, and therefore before the Hurricane Cliffs were there. Bob Biek (2003, Geologic Map of the Hurricane Quadrangle) estimates the age of this gravel at middle Pleistocene. Since they contain basalt cobbles, they are probably younger than about 1.5 million years. Therefore the entire canyon and its interesting features are geologically quite young.
Test Drilling by the US Bureau of Reclamation in the 1950’s for the proposed Virgin Dam, named for the town of Virgin which it would have flooded, found rock so fractured, cavernous and permeable, that they walked away from it and never looked back. The sink-hole that swallowed the river for 3 months in the spring of 1985 and recharged Pah-Tempe hot spring is described in Everitt and Einert, 1994 (Utah Geological Association Publication 23, p. 189 – 194). These interesting geologic units underlie much of Washington County, and are sure to present challenges as future development moves out into the hinterland.

Tuesday, November 13, 2007

Volcanoes Near Hurricane Fault exit westward with time

Sullivan's Knoll, SK, west of Hf has basalt base age on order of 200 kybp, cone at 10 kybp

Grass Valley Flow (on Hf, Hurricane fault, south of town 15 km) is slightly less than 1 mybp in age

Cones and Domes are Generally older than 3/10 mybp (.3) East of Hurricane Fault; shown is Crater Hill, near Virgin Town

Monday, November 5, 2007

Slickensides in the Hurricane fault zone (scarp)

These Slickensides are more extensive on hiway 9 cliffs, east of the shoulder, on the north part of hte Graben
This is the most massive Slickensides found- you should study it to use as an
Example for Future Finds; notice the Linear Striations and Grooves of hardened surface (probably silicates) precipitated from warm water flowing along the previous Subsurface Fault Face (original composition was Limestone, CaCO3)

The South view of Graben shows where it started (Water tank sits on Graben Downthrown Block)

Westward, the Upthrown Block shows a 15 Degree departure from Vertical (West Edge of Graben wall moved northward, as well as Vertically)

Eastward, the Upthrown Block Has Almost-Vertical Striations, indicating that the Plunge to north has little influence on the orientation
Graben Slickensides show Direction of Crustal Movement

Shown above and below are photos of “Skid Marks” or slickensides in the walls and Scarps above the town of Hurricane, in the Hurricane Fault, Hf to the east. These are the result of the rasping of one block of the Crust, as it moved relative to another block which is more stationary. These are primarily the work of normal faulting, which is unknown as to origin, but they give details of the movement in one local area. They may yield understanding of the larger underlying event which has Hf as a final result. The movement which produced the slickensides is very deliberate and slow, so that the final product is slick and contains regular lines and a glassy portrait of the direction and type of movement.
First, notice that the surface of the slickensides is so well-polished that it shines in the sunlight. The two blocks which slid relative to each other are of similar composition, and therefore of similar hardness. This causes the honed surface to appear extremely fine-grained.
Secondly, the surface is discolored in the millimeter or so thickness which is preserved. This is caused by the heat which is generated by the friction of rubbing, which changes the solubility of compounds in the water which has found the fractured and faulted space. The drop-out of iron compounds and other solutes in the water makes the surface harder than it was originally- initially calcite or limestone, which is soft (3 on Moh’s hardness scale).
Thirdly, small grains of hard material entrained in the moving block remain un-dissolved long enough to leave a line or trough, which indicates the direction of the movement. For a graben, this movement should be vertical, since this is a normal fault, happening under extension. However, the deviation from vertical is striking and regular for the west wall of the graben, which is the upthrown block (the downthrown block cannot be seen, because it has fallen into the earth).

Preliminary Conclusions:
1. The west wall of the graben has slickensides with striations dipping down into the earth- Down-to-the-South. Since the graben plunges down to the north, part of this 15 degree angle is due to rotation of the graben as it plunges down to the north (look at the larger photo of the whole graben, where the incipience or start of the graben is shown to be less than a kilometer to the south).

A Closeup of east wall of the Graben shows Striations resulting from "Drag" of Downthrown Block hard pebble inclusions- which leave parallel grooves.

2. The east wall of the graben (again the upthrown block) has a few degrees dip down to the north. This is not significant, and may be approximated as vertical, but the importance is that it shows that the plunge of the graben to the north is not a significant contribution to the deviation from vertical.

The Detailed Closeup of Striations (East Wall) show the angle of deviation as less than 5 Degrees, indicating that Plunge of Graben is not the Primary Factor causing the movement away from Verticality in the West Graben Wall
3. Since the graben west wall is the one showing deviation from vertical of the drop of the downthrown block, this indicates that we are looking a phenomenon which is occurring closer to Hf proper. Although the entire graben is part of Hf, and there is transfer of stress to form the graben, the entire result can be interpreted as part of the total movement of Hf. In this case, generalizing, the rim of the graben is moving north with the time of fall of the graben relative to the downthrown block. This would be a right-lateral fault, with movement laterally caused by something other than gravity (a weight of rock simply falling- due to gravitational attraction- as the earth is pulled apart). The lateral movement would be due to a compressive force, such as rotation of the Colorado Plateau, CP.
4. This right-lateral faulting is representative only of the graben where it is found but could be an indication of further investigation to determine whether it is representative of CP as a whole (at least on the western side, near the Pine Valley Mountains and local volcanism which bear on it- all Post-Laramide features).

The Massiveness of the Slicks shows that they were the Result of a continuous Sliding, and the Regularity indicates a slow movement which was heated by the Friction- allowing Water to Rearrange its Chemical Contents over significant time (NOT lurching)

A Rare image shows that there was occasionally a Disruption in the Graben Sliding- an interference