My Sediments Exactly EarthCache

My Sediments Exactly!!

First and foremost: Access to the cache site is not recommended during the Spring months where snowpack runoff is high. This Earthcache is located along the creek which can be hazardous during high water flow, but the area is very impressive non the less. The site is accessible from either side of the creek during the summer months when the water flow is low. The easiest access is from the Pioneer Trail on the West side of the creek (Some rock scrambling required). Parking is available where Bowman Road crosses the creek to the south of the site. This is also a VERY POPULAR swimming hole so bring your suit!!

The formation of the Earth is a slow and complicated process. But you can find a record of the process just about everywhere, if you know what you are looking for. In the case if this earthcache, the results of sediment deposition can be observed.

Sedimentary rocks contain important information about the history of Earth. They sometimes contain fossils, the preserved remains of ancient plants and animals. Coal is considered a type of sedimentary rock. The composition of sediments provides us with clues as to the original rock. Differences between successive layers indicate changes to the environment which have occurred over time and sometimes the type of material deposited. Sedimentary rocks can contain fossils because, unlike most igneous and metamorphic rocks, they form at temperatures and pressures that do not destroy fossil remains.

Formation of Sedimentary rock is an easy process to understand. Very small particles of materials are suspended in water, like a river or stream, and are carried down stream until the water flow can no longer carry the material. This sediment can be smaller pieces of broken rocks, sand, or pieces of lighter materials, like dead animals or plant parts. When the water flow slows to the point on not being able to carry the material it settles to the bottom in a layer. (See Diagram for an illustration) Sediments can also be carried by the wind if light enough. The only difference is that the sediments get deposited in an area where the wind current slow to the point of not being able to carry the material anymore.

The sedimentary rock cover of the continents of the Earth's crust is extensive, but the total contribution of sedimentary rocks is estimated to be only 5% of the total. As such, the sedimentary sequences we see represent only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks.

About this site: At this Earthcache location you can observe the resulting sedimentary rock formation created by the process above. This example has been brought to the surface thought the formation of the Sierra Nevada Mountains. The formation has been further exposed by the creek bed in which it resides. The water from the creek has washed away the loose rock (continuing the cycle of creating a new generation of sedimentary rock further down stream) to expose the layers of this location. The layers of rock at this location are of a higher density than typical sandstone, however, you can observe that the hardness of the layers varies. This is evident from the erosion present due to the water flow of the stream. The softer the layer, the deeper is it eroded. You will also notice the "orientation" of the layers. This was caused by the rising of the earth crust in the formation of the surrounding mountains.

To log this cache: (Email me the answers)

1. At the given coordinates you can see three main layers of rocks. What is the difference between the middle gray layer as compared to the layers on either side? I am looking for anything but color here. Consistency/texture, the effects of erosion, etc.

2. Estimate the width of this layer.

3. Explain the "orientation" of this sedimentary rock formation in relation to the horizon. (Horizontal, vertical, diagonal?)

4. Do you think this orientation influences the direction of the creek flow. Yes, or no and why?

Remember, Practice "Cache In Trash Out"

While out geocaching, bring a bag with you to pick up trash along the way.

Visit the Cache In Trash Out page to learn more about CITO.

CITO Logo use granted 3/28/08 by Groundspeak BTG-708616