Tuesday, March 6, 2007
This is all "For the Birds"
Assessment of Death Valley Movements
There are several photos, shown in this Blog, which allow some evaluation of the current fracturing and faulting in the DV Park. The reader should evaluate all of these photos, with a view toward understanding the recent slicing of the Earth. First, since DV has a sink where the elevation is below sea level, this means that erosion from the nearby high mountains is unable to fill in the valley faster than it is being lowered. Normally, hills are rounded with erosion, since they are attacked by weather fairly rapidly. Since this is not the case for DV, the prominence of angular features accentuates that they are currently active, offsetting erosion. Active fracturing and faulting (fractures which exhibit lateral or vertical movement) revive the angularity of rock outcrops seen at the ground surface.
First, there is a young volcano (less than 1 m.y. age as measured independently by radioactivity), which has been cut by an on-going fault- shifting the west side of it to the north, relative to the east side. The erosion is still pronounced, since the extrusive ash and rubble is soft, but even so you can readily see that the volcanic mound has been shifted in a right-lateral manner (that is one can stand on either side of the fault and determine that the opposite side has moved to the right). This fault has a north-south slicing, showing that the current stress system is oriented similarly to that seen in the transition zone in Utah, for the most recent movements (refer to Coal Pits Canyon and the youngest orientation of the Colorado and Rio Grande Rivers- which is N-S in the website www.geocities.com/overtonharold/- this is a link shown o the right side of the Blog, or at the bottom for simpler dial-up connections).
Second Photo shows a map which allows the general orientation of DV to be examined. The south part of the park has an orientation of N-S, while north of Artist Drive it is more NW-SE (closer to 155-335 degrees from north). That is the north portion of the park has been subjected to shearing stresses which are some 30 degrees at variance to that in the south. This is generally observed in AZ and UT also, from field work performed by myself,
The question remains: Is there N-S orientation the younger, or are both of these stresses intermittent? In the Colorado Plateau transition zone CP, my assessment is that the N-S stress is the younger, but it may be that there are pulses of both stresses occurring at different times.
I was interested to find the outcrop of rock which would show the location on the ground surface which showed the transition from one set of stresses to the other, as seen by fractures. This serendipity was found not by me but by the ubiquitous Raven.
Whimsically, he is photoed sitting on the signpost to the entrance to Artist Drive in south Death Valley Park, announcing esoterically that “This is the Place-Evermore”. See the photo which has the ebony Bird, which was sitting, never flitting near the entrance of the park road and to my Serendipitous Camera Door. HLO