A Bit of Southern Utah in California EarthCache
A Bit of Southern Utah in California
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This earthcache shows the diverse geology of the Sierra foothills and the central valley.
The central valley was formed when the coastal ranges were formed by fault action. Before this it had been the bottom of the young pacific ocean. The rising hills to the west cut the valley off from the rest of the ocean and eventually it dried up. The bottom of this sea was made up of limestone and sandstone.
To the east, the area of the sea there was also pushed up the colliding tectonic plate about 130 MYA (million years ago). This caused a volcanic range made up of mainly granite with some basalt to form.
As the two plate collided here, the now dry valley floor was forced up against young Sierra Nevadas causing the rocks along the borders of these plates to form new kinds. This can be observed at nearby Merced Falls were both shale and slate are visible.
At this location we can observe a very interesting formation that shows these forces at work. It appears to be a combination of granite and sandstone. It also shows that the sandstone here has a high amount of iron in it. As the iron becomes eroded to the outside of the formation, a process called oxidation occurs and turns that iron into iron oxide. Giving this formation a redish tinge.
To get credit for this earthcache e-mail me an answer to the following questions:
1) The name and GC code of this cache.
2) The number of people in your group.
3) What is the common name for Iron Oxide?
4) Post a picture of yourself or your GPS at the formation.
5) What color are the border regions between the sandstone and the granite?
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