Thursday, June 25, 2009
Coriolis Influence on Moving ice- Glaciers
Coriolis Influence on Moving Ice
Coriolis Forces are omni-present on the moving Earth- occurring due to the differential velocities of moving mass positioned across Latitude lines. The further away from the Equator a mass is positioned, the slower the horizontal velocity from Spin- becoming zero at the North or South Poles. Equatorial movement is greatest, since the spin of the Earth creates the fastest surface movement there. Consequently, moving mass tends to turn to the right in the Northern Hemisphere, since the velocity is greater on the south side than the north. As a result, weather cells with low pressure incur winds which blow to the center of the cell and are forced to the right, or Counter-Clockwise. High pressure moves outwardly and, with right movement, winds spin CW. As a result of all this, continents and large islands incur rotation everywhere except exactly at the Equator- where there is maximum velocity due to spin of the Earth. A photo of South America shows that the continent has spun CW, creating a “tail” trail of islands and arcuate coast line at Tierra del Fuego:
This rotation of mass occurs at small time intervals, so that we dn't have to have millions of years of history for a recognizable geometry on a map. I have found that volcanoes with emerging lava incur rotation CCW, and later present CW rotation as cooling and shrinking occurs- even on the 100 kyear scale. Such a case has been documented in southern Utah for the Grass Valley and other young volcanoes, which are cooling and rotating CW (from slickensides and cracked slabs of concrete).
Above is a photo of Mt. St. Helens- a recent volcano, that is obviously still active and therefore rotating CCW (for rising features). A small stream has been diverted by the rotation- shown on the lower right side. Since this stream probablly has been photographed before the eruption, this represents a case which could be documented for rate of movement along the stream bed (the eruption has increased the rotation rate). I have found 5 mm/yr, for cooling vulcanism, and this case is probably faster. Try your hand at finding old photos of the stream and then measure the displacement to calculate the rate of movement.
Below is the expanded photo of the stream shift. Although the westward extension is not obvious, the shift of the east stream is clear. Some field work should be performed here to confirm the movement age.
A corollary to all this Coriolis movement is pertinent to the Equatorial Bulge, EB. Since there is an extra thickness of the Earth due to centrifugal force slinging mass outwardly there and to the attraction of the moon, there is added Coriolis influence in this zone. This is an observation, since it appears from case studies that the movement laterally of the Crust is independent of the Mantle- the movement being unable to be transmitted across the Asthenosphere. Consequently, continents rotate more rapidly in this 40N to 50S latitudinal EB zone than further away for the Equator. The thin Crust of the ocean basins incur less rotation than thick crust of the continents, and exhibit almost-straight lines of shear (transforms), rather than obvious circular features.
How about ice from Glaciers? This is a classic case, where ice moves downhill with measurable horizontal velocity- which should incur movement to the right. An expected complication occurs due to vertical velocity of weight-incurred ice movement- sinking while ice builds up and rising due to rebound with melting.
The first case is a simple one- that for Holmes Harbor- which exhibited movement southward during the last Wisconsin glacier stage. The trace of the ice may be seen on LIDAR maps as N-S linear traces creating river ways and with etches on large boulders on Whidbey Island (Examples include Goose Rock and Rocky Point). Below is shown a Google Photo of Holmes Harbor, which lies alongside N-S creeks such as Chase Lake and Honeymoon Lake drainage. Maxwelton Creek in the south of the island is a perennial stream which flows along a south drainage, except for a lower NW-SE tributary under the influence of faulting.
Notice that Holmes Harbor has a circular appearance, turning to the west as the ice moved to the south. The termination of this lobe is at the town of Freeland, where moraines and drainage ways can be seen there to document that the ice moved no further and was the last of the glaciation to move southward. If we assume that the glacier moved over a measurable time interval, the rate of diversion to the right can be calculated (about 2 km/10k years, or 20 cm/year). This is no more than an estimate, but could be measured accurately for precise dating and lateral distance determination. This estimation is large compared to that measured in connection with volcanism. One principal reason for this is the viscosity of ice, compared to that of rock surrounding a rising magma (as much as 20 kilometers distant, rock is found to have shear and horizontal slickensides occurring in a circular pattern). Even common limestone, which is visibly plastic- moving noticeably in a lifetime- is much more resistant to shearing stress than ice, salt, or shale. Consequently, movement of cm/year rather than mm/year for sandstone can be expected. The time scales are the main variable- being less than 50k years for glaciers, compared to 100k years for the volcanoes studied.
A more complex case is that for Penn Cove- which is the next glacial depression to the north. Penn Cove moved 250 degrees form north or almost westward. This can be seen from LIDAR maps, as an overlay onto older southerly traces of glacial movement, and from orientation of the waterway itself. Since the fresher track obviously obliterates the N-S traces, it is younger, and it terminates at Ebby’s Landing waterways and near glacial Kettles to the west. This ice movement created an arcuate depression as it moved westward, but is complicated by a reversal (left diversion) near the middle of Penn Cove. I have found that sinking (cooling) magma chambers exhibit CW rotation (versus CCW for heating and expanding volcanoes). It is possible that sinking ice lobes- due to their weight- would accentuate the CW rotation exhibited in the photo, on the east side. The reverse on the left (west) side would be a CCW rotation for rebound or uplifting areas, and this could explain the reversal noticed for Penn Cove. Rebound would not be expected for increasing weight of ice, so that uplift would have to be documented (incurred during westward movement of the lobe). We will try to document this effect by cliff study west of Monroe’s Landing on the north side of Penn Cove.
Added information is shown below for the east part of Penn Cove, where an iron spring indicates that exotic behavior occurs.
The iron springs obviously contains double valent iron- which is oxidized upon contact with the air (changing into the tri-valent insoluble form). This has formed a cemented gravel ramp at the edge of the tidal zone.
More likely, the left deviation seen for Penn cove occurs due to ENCOUNTER OF THE MOVING ICE with a sinking subsurface CW-rotating Coriolis cell (which could still be rotating). Estimating that at least 10 kyears have transpired since the lobe moved westward, this yields a left movement of about 2 kilometers. This is estimated from the Holmes Harbor case, with 20 cm/yr displacement. The total rotating cell movement can only be extrapolated, since only the underwater portion can be seen. EXTRAPOLATE THE SHOWN PORTION, USING A CONSTANT DIAMETER, and the projection would have influenced the western wall of the previous ice lobe.
Above photo shows only the west portion of Penn Cove- where there is a left diversion. This portion is subject to a different action compared to the east side.
This area is a popular location for hiking, viewing the glacial kettles (a half kettle may be seen north of Perego Lake, from the trail there), and viewing the rich soil found on the north, south and east sides of the Cove. The old drainage from the glacier was to the south- avoiding the highlands of the Kettle area. This area is still rising from hints I have found walking the beaches to the west. Conversely, the area to the south has lowlands, sinks, and peat beds.
Above is shown a photo of the cliffs at Coupeville- which is near the intersection of the two ice lobes. The Holmes Harbor is a south-trending glacier, and the Penn Cove is a result of a later movement to the west. There is interference between the later thrust and sliding ice and the earlier southern movement.
This may all be seen by walking a few hundred meters to the west below the boardwalk near the museum in the town of Coupeville.
The solution to the left deviation in Penn Cove is shown above, if you can interpret the trace underwater. My analysis, considering cases I have analyzed from the SW USA, indicates that a rotary cell to the west of the Cove has caused the Crust to move laterally. The direction must be checked with measurements on the scarp, but the incipience appears to be on the west side (CW).
Looking at the photo above, an extrapolation toward the east can be made for the portion of a rotating cell shown on the west. For this scenario, the west side of the ice lobe would have been shoved to the south- yielding a left diversion for the western portion of the Penn Cove ice lobe.The new presentations are much younger than those studied previously. We are dealing with only 10-50 kyears, for these last ice movements, and rotary movements are only partially presented- they are ongoing, with active rotation incomplete (compared to Tertiary or Mesozoic portraits).
Information from the Great Lakes glacial region:
Before carrying this to its extreme, look at the larger expression of glaciation- the Great Lakes, which had more episodes of ice advance than the NW Puget Sound area. Notice that the rotation is to the left for Lake Michigan and Superior. Is this evidence of a failure of the Coriolis Theory? Remember that rotation is CW (this case) for sinking or shrinking Crust, and CCW for rising earth. This is a larger picture, encompasssing several states, and more is going on here than just right deviation of a single lobe of ice.
Niagara Falls is the simplest expression of rebound (rising Crust), since the Crust is rising faster than can be eroded. This is the present condition, with rebound occurring AFTER the ice has retreated. The rotation would be CCW for rising earth, but during the ice age with active advance, the Crust would be depressed below the ice lobes. Sinking earth should rotate CW, the opposite of normal tectonics. Sinking (depressions, sinks and downward movement) should exhibit the opposite of uplift, volcanoes, and salt domes.
My conclusion is: the multi-state region is rotating, or has rotated while ice was forming, in a CW movement- offsetting the rightward movement of individual lobes while advancing- and resulting in apparent ice movement to the left (spiraling of ther Great Lakes is CW- dragging the Crust and its overlying ice.) In other words, the Coriolis rotation of the Crust (the whole region which was covered with ice) was not effected only in single lobes (which are a small part of the "Big Picture"). The overall effect was larger than the rightward movement of one ice lobe (which is shown in the photo, trending left-ward).
Above is one scenario for erosion, river formation, and rotation of the general area.
A photo of Lake Michigan is rotated 90 degrees, so that you can see the effects of glaciation and rotation for yourself. Etches in the bottom sediments and rock may be due to shear, siltation, currents, or movement of the Earth.
Below is a photo of the Mendocino, CA location- showing the area of my next investigation (I will visit it this August). This is an important area for clues for the tranistion of Coriolis rotation to shear, going westward under the Pacific Basin.
Part of the interesting features near Mendocino is the Fern Canyon State Park, near the mouth of hte Klamath River. The rver is part of a Coriolis cell, evidently sinking- causing CW rotation. We will check this along the K. River, to see whether slickensides have fornmed on the canyon walls.
Below the photo is rotated at right angles to show more of the canyon area. Notice that there is a partial cell, which seems to be dragged CCW (I'll check this in the field, since this is my greatest source of error- finding drag and rotation direction.
If my analysis is correct, there is counter-rotation crossing the klamath River (so that there is no shear and subseqaunt metamorphism or heat produced- since the cells rotate as gears with no interference).
The photo below is used to investigate whether a subtle change such as sufficient uplift to cause a meander to silt up can be noticed on the Google Earth map. There is indeed a small circular portrait for half of a rotation. This is only for a one meter uplift or siltation, so that little credence can be attached to it. But the feature requires further investigation, since this may have enough upward movement for the Coriolis Forces to create a discernable effect.
Another feature to investigate this summer 09 is that of a rotating cell near an oilfield- Petrolia, CA (which is near Mendocino and Fernm Canyon). We will hike this area with a view of finding any evidence of slickensides, fracture parallelness, and shear in the rocks. This is shown below:
TO BE CONTINUED