Tuesday, May 19, 2009
2009 Whidbey Island hikes and analyses
Above is a Google map of Whidbey Island, where 2009 summer hikes will be conducted. Our goal is to document the movements of the island in the various directions: rebound, shearing, uplift, rotation, sinking, and linear faulting.
This starts the summer hikes on Whidbey Island, where I have documented movements of the Crust- by weekly hikes along the beaches. These are seen mainly by parallel fractures in glacial till, but there are some visible faults. Introducing these via Google Photos, above is shown the BIG PICTURE- where the Mesozoic makes contact with Recent till (as young as 14k years, bp) on the north part of the island, via lateral faulting.
Items above are an unsolved enigma, showing plots for the numerical ALKALINITY in water wells. There is a regularity to the graph of Alk/Cloride on a geographical map. This is perpendicular to the faulting known to occur on South Whidbey Island. The plot is parallel to the inlet and eroded portion of the island. I have found that alkalnity, which correlates with bicarbonate in water, is a good indicator for solution of calcereous cement in soil or PRESTONE. When acidic rain dissolves the cement, preferentially via fractures at the ground surface, the soil is weakened and erodes further, and slumps in large blocks into the nearby sea. I have included a bare map, so that you can print and make your own interpretation. Since Dr. Eaton was shown this and he doubted the veracity of interpretation, and later plotted it himself without further admonitions, I assume that it is a good interpolation. However, if you find that there is a different interpretation, make a comment on the Blog below.
Notice that there is orthogonality presented- perpendicularity with the SE Maxweton fault. In addition, there are two circular presentations in the Bay bottom, indicating that Criolis rotation takes place there. This is more information to consider to form an analysis of the whole feature of HCO3 ion concentration, faulting, and rotation of the soft weak silt bottom sediments.
ITEMS BELOW WILL BE INCORPORATED INTO SUMMER 2009 HIKES ON WHIDBEY ISLAND
Admiralty Point to Baby Island fault zone
While walking the beaches near the village of Ledgewood (Central W.I.), several anomalies can be spotted:
a. To the north of the public access parking area at the Village of Ledgewood, about 100 meters, there was a house sliding into the fault zone for several years. During 2008, the debris was removed, and only a slump zone can now be viewed as the main evidence of a left-lateral fault. A nearby resident showed me her garage slab, which was separated form the house slab by a 2 x 4 horizontal wooden upright. The nails holding the 2 x 4 were bent southeastward- indicating that the northern portion of the house slab had moved NW-ward;
b. There is considerable evidence of sedimentary beds tilted down to the west, at the beach 1 km south of the downramp. These are thin siltstone or white beds with angular edges, indicating that a local fracture had opened, allowing the white beds to slide into the fracture (which was subsequently buried by glacial till and finally exhumed by wave erosion of the island inland);
c. Following a SE line toward Baby Island, first, a spring and wetlands are encountered on the eastern side of Whidbey Island. Refer to the Google photos to see all of these anomalies;
d. Hancock Lake is anomalous-a depression- and it continues to erode via its connection to the Admiralty Passage. At one time, cranberries were raised in the lowland, but seawater continually entered through the eroded and sinking inlet; NOTE: I have found that Coriolis forces act on a mass which is thinner on one side, compared to the other, by elevating the side with thicker mass and depressing the side with thinner Crust (in addition, the diameter of the rotating cell may be estimated- in this case, about a km or so);
Finally, at the beach near Saratoga Road, in the shallow waters toward Baby Island, there occur two parallel fault tracks, similar to subtle hogbacks (raised into the air by buckling). These indicate that Baby Island is separated from the main island by a fault zone. One may walk to the island during low tide, and can walk on top of these few inches-high scarps (see photos of thee features below):
My initial and current analysis is to place a fault line along the NW-SE orientation, from Admiralty Head (which exhibits a nearby saddle in the hilly land). The fault zone at Ledgewood is spread over a kilometer, with the slippage found over the entire interval- where considerable shear is caused by the left-lateral fault. From the accompanying photo, there occurs a line of shear near Hancock Lake, with no obvious connection with the fault at Ledgewood.
Of course, there is a zone of shear, which distributes the few millimeters of movement yearly along at least a kilometer of beach. On the south side of Hancock, almost horizontal thrusting can be seen in the cliffs- indicating beds sliding over the same beds. I initially was torn between classifying them as due to the latest glaciation (its surface moving southward) - shoving the older scarp to the south- or to shear from below (northward movement of the basement). Every year the thrusts become more faint, and it appears that the soft sedimentary beds and till do not show that there is significant penetration of the thrusting to the east- into the cliffs. These beds have enough strength to remain competent, but shear easily- leaving vertical cliff walls.
My main conclusion is that a wide zone of shear, caused by Coriolis rotation (see the circular dark zones on the Sound bottom) has created both Admiralty and Greenbank bays. We will hike all of these beaches again, to determine whether there are additional springs and anomalies, which bear on the analysis.
The map of Admiralty Point to Baby Island does not agree with my previous assessments found on the beach hikes (at least 10 over the years).
The first complication has to do with the time which is required to shear and leave a noticeable anomaly on the Google Earth map. In other western USA analyses, I had at least 200k years minimum time for the rotations to transpire (for the Hurricane, UT vulcanism to wax and wane- the simplest case). Whidbey Island and the latest gouges in Admiralty and Saratoga passages have been uncovered from the glaciers only 10k years or so. I see Coriolis rotation traces on the above map, but these are only part of the expected encirclement. Estimating the maximum Coriolis rotation at 5 mm/year, the movement since the glaciation would be no more than 50 meters in length. This photo demonstrates that the shear marks on the sea bottom are less affected by weathering and LIFE, compared to that on land. I expect that the deep water absorbs most of the Coriolis rotation (the water moves by tidal action, whereas land mass rotates- because it is available for Coriolis force and earth tides). We sill take informtion from all sources available, using beach observations tempered with the Google photos. Next we will hike the Greenbank and Lake Hancock beaches again, to find the latest developments.
The first reason why geologists cannot see Coriolis rotation is because of lateral shear leaving little displancement or trace in soft sediments. Note that the cliffs above show nothing but monotonous circular presentation- even though the offshore deep water exhibits a circular mark on the seafloor.
Below are remarks made for practical interpretation of the beach hike of 18 May/09 and of a Google Earth photo which allows for analysis of the dynamics of this young feature. The photo shows that there is only half of the Coriolis cell presented, and we will try to determine why the west half is obscure. The general rules I have found for all Coriolis rotations are followed for the half presented:
1. The side of the cell which has less mass rotates slower, and presents a sink due to the lag;
2. The side which has the greater mass rotates faster (F=ma) and presents an uplift. The diameter of the cell will be determined by the distance between these two contrasting entities- in this case about 3 km;
3. The presentation is circular, regardless of the diameter. Even continents are circular (note the circular configuration of CA coast or of northwest Africa), and the rate of rotation is on the order of mm/year; and,
4. The center of the cell will have a linear feature crossing the entire cell, e.g. the Hurricane fault divides a cell at the town of Hurricane, UT. In the W.I. case, there is an uplift which has springs seeping into the village of North Bluff.
Below are photos baken during previous years, showing the anomalous behavior of cliffs and faulting found about the Hancock anomaly;
Above photo shows the rise of the Esperance ss. in the low tide saddle between Baby Island and Saratoga Road, W.I. (in parallel tracks which point toward the main island and the Greenbank anomaly).
The rise and faulting shows up in a nearby bulwark as a vertical shear in the photoed wall.
The anomaly can be traced in the cliffs, where thrusts and shear faulting are photoed just south of Hancock Lake- a depression opposite an uplift, or scarp just north of the Greenbank store.
The buckling and thrusting is seen in the N-S cliffs just south of Hancock Lake, as gravel beds jammed against each other. Each year the portrait is different, due to spalling of cliffs after storms. The penetration of these obvious features into the beds to the east is scant- indicating that the shear vertically is predominant, while the lateral influence is minimum. This would be the case for curved plane vertical shearing, due to Coriolis cells rotating laterally- yielding thrusting along the vertical thrust plane. Further to the north, a house has slumped into the ravine created by the action of the fault system going from Baby Island to Ledgewood subdivision. There is a NW-SE left-lateral fault cutting through the area, as evidenced by a garage concrete slab being shifted relative to the main house slab.
THE PRINCIPAL DIFFERENCE BETWEEN OCEAN BASIN BOTTOMS (Deep water)AND LAND MASSES IS THAT OF MASS THICKNESS DIFFERENCES ABOVE THE ASTHENOSPHERE- continents have a much greater protrusion than does the thin crust of the ocean basins (and the great depth of water evidently absorbs most of the tidal influence of the moon). I am now investigating whether the effect can be found inland in shallow bays.
Red lines refers to assessments made during beach hikes, the purple arc is found from inspection of Google Earth, and blue refers to my analysis. A scarp and accompanying sink (such as exists at Laverkin, UT at the Hurricane fault, Hf) help define a Coriolis rotation boundary and diameter of the rotating cell. For Admiralty Bay, the radius of the Hancock-Greenbank scarp cell is small- several km or so- and not likely to pertain to the larger 10k year rotation seen on the map (only a fourth of a circle is seen on the sea bottom). This Coriolis cell is not definitive for the larger view, and has evidently been obscured by the fast tides and erosion occurring in the Admiralty passage- notice that there is no evidence of shear, except for the tidal grooves. Whatever was sheared or rotated has been eliminated from view by fast currents and siltation. However, Saratoga passage (to the east), similarly to Admiralty passage, has also incurred glaciation, siltation, and scouring.
Below are photos taken in May 09, which are different from those seen in 08. Thrust faulting has diminished from three to a single thrust today. Should the penetration laterally be scant, this could easily be sloughed off yearly. When circular lateral shear works along the beach, this could result in vertical shear planes along small mass thickness east to west (the plane of shear presented vertically, N to S). Sloughing woiuld remove the shear planes yearly, allowing a new vertical plane to be presented.
Hiking the west Hancock beach, from the south near LAGOON POINT, a thrust fault can be seen in the cliffs. These thrusts have appeared for ten years, but the cliff spalling, due to storms, present a different picture each year. It appears that the penetration into the cliffs is not deep. Should there be a vertical plane of shear, N-S, this would have the fault plane along the beach, with little penetration. This would be the case for circular shear parallel to the beach (creating the cliff orientation). We will follow up on this conjecture with hikes to other anomalies found in previous years.
Photos above and below show a known fault zone, at the beach at the village of Ledgewood, W.I.,which has caused a house to slide into a canyon (at the left lateral faulted ground surface). Although displacement may be measured via a concrete slab, it is difficult to appraise in soft Quaternary sediments (ESPECIALLY IN GLACIAL TILL).
The reason why Geologists can't see this, occurs because of the nature of the shear which creates it. The shear is vertical, actng as a rotating plane (the diameter of the rotation being large enough so that the shear appears to be linear), creating vertical cliffs which are in the plane of the faulting.
Above photo is a telephoto of the preceding one.
Further south, about 2 km, the same strata may be seen to be dipping oppositely, due to undulation along the fault plane.
A new photo shows my interpretation of the entire entity:
My appraisal on the photo is based on observations of other Coriolis cells and half-cells found on the young sediments in the cliffs at Whidbey Island (for the Ledgewood fault and its effect on surrounding soft sediments and seabottom):
a. Cells are formed and react to the shear or movement created by lateral faulting, with the fault being the driving entity (THERE HAS TO BE INDEPENDANT MOVEMENT FROM ANOTHER SOURCE, FOR CORIOLIS FORCES TO OCCUR):
b. Actively-moving fault planes create reactionary cells, rotating horizontally about the vertical expresssion of the fault plane, whenever there is a difference in elevation (Crustal mass thickness) between two locations along the plane;
c. The rotation AND DIRECTION will have to be measured in the field, using information from the cliffs, and in this case thrusting of beds over each other;
d. The movement is on-going, and is incomplete (for the total circular presentation) for these sediments younger than 100k years.
MANY CORIOLIS CELLS FOUND IN THE WEST USA HAVE A CENTER LINEAR FEATURE (SUCH AS THE HURRICANE FAULT, UT), WHERE A HORIZONTAL CIRCLE IS INSCRIBED (with arcuate river valleys) ABOUT VERTICAL FAULTING OR OTHER LINEAR FEATURE).
EXAMPLE OF A CLIFF SHOWING GLACIAL INFLUENCE OF MOVEMENT: Holmes Harbor is a glacially-formed indentation in the Crust. The weight of the ice has pushed the seafloor down, and Coriolis rotation has made an arc of the bluffs surrounding bluffs associated with the previous southward linear of ice. The movement, using at most 5 mm./year can be 50 meters laterally in 10k years.
Another curiousity on Whidbey Island, is that of Double Bluff, which erodes at least 1 ft/year with the winter storms. Nevertheless, it remains- protruding westward- throughout the years. It sticks out into Admiralty passage, accepting the worst of the storms. A photo of it is shown above, so that you can see how it is moving: Notice how the cliffs shear with winter storms- vertically, oriented almost E-W (260W). This indicates that Coriolis rotation has weakened the sandstone along the rotating direction- vertically, not horizontally!
My analysis of the movement is as follows:
Below is my appraisal, which allows for rotation and jutting greater than the storms can erode the protruding cliffs of Double Bluff:
Another interesting feature on W.I. is a tombolo- near to the mapped Utsalady fault on the NE side of the island. Polnell tombolo appears to be dragged by the fault plane- which is left lateral. that is, the Coriolis circle shown on the below map should be rotating CW. However, the newest-appearing scarp lies on the north side, which would make the rotation CCW. Furthermore, the "drag" on the beach to the north of the tombolo seems to indicate CCW rotation (although the tombolo indicates opposing CW drag). We'll do further research on this, since USGS mapping infers that the fault is a normal one, not a left-lateral as has been found for most of the island's large fault systems. Investigation of the basin east of Polnell tombolo may yield more information, since USGS PP 1643 shows several splays to the local fault system near this beach and on Camano Island.
Here is the undoctored photo, so that you can interpret it: Hiking on the beach of the tombolo (July 31/09), there occur a number of interesting feastures. the first is shown below: a large E-W fracture on the east side of the prominence, which disects the tombolo.
The photo above shows that the tombolo is a separate feature compared to the rotating seabottom trace. The centerline does not align with the E-W fracture orientation for the above-ground tombolo. Their rotation evidently meshes, there being no obvious hot springs or heat produced. Photos below show how the offshore Utsalady fault trace orients to the NW- where Crescent Bay occurs.
Compare the tombolo shown on Polnell with a protrusion on the Olympic Peninsula, WA, where there is a spit nearby, with faulting influencing both entities: There is a circular underwater scarp, which is concentric with the cape jutting into the Juan de Fuca strait. The west end suggests that the incipience occurs there, and the diversion to the west of the ELWHA river valley indicates CCW rotation (REBOUND,after the Pleistocene ice age). Further, the underwater trace of the NW-SE fault system can be seen just to the west of the circular trace. Although I have not plotted the known lateral faulting,it is published in various professional papers. The LINEAR feature in the center of Coriolis cells is common- being the entity creating the movement, upon which Coriolis forces act. NOTE: CORIOLIS IS A FORCE CREATED BY SHEAR (OR STRESSING)BETWEEN ADJOINING LATITUDE LINES, WHERE THE GREATER FORCE ON THE SIDE NEXT TO THE EQUATOR ACTS on that side MORE STRONGLY, AND WHERE THE GREATER PROTRUSION OF MASS (crust) IS DIRECTLY RELATED TO THE VELOCITY OF ROTATION OF AFFECTED CRUST.
Other observations found on the beach hike include:
1. Layering is regular and flat on the east side of the tombolo, compared to buckling and dipping on the west side;
2. Moraines previously lying higher in elevation (and now contrasting with siltstones nearby) have marked the edge of a glacier lobe. These lie near cliffs, which have fine-grained sediments which are layered (not till or random deposits); and.
3. The picture is one of a RC, reactionary cell, which is dragged adjacent to the main Utsalady fault as it moves westward on its north side (left-lateral).
The region I will analyze next is that of Mendocino, CA, where a major transform intersects the coastline (Petrolia), and which is modified by Coriolis rotation. This is seen above in a photo with an obvious cidrcular river valley presentation near the coast. I will attempt to find slickensides or other fractures in the rocks above the rivers, to determine the roatation of the large cell.
Below is a beach photo, taken from Google Earth, near the Klamath River. This Coriolis cell is partly shown by the River pattern (from erodable fractures), and partly by the trace on bare earth. Note the shaeared groundsurface:
We will hike the beach to the south, to determine whether there are scarp indications, or whether this is just an eroded beach front.To be continued.