Cache la Poudre River The Cache la Poudre River or the Poudre River as locals refer to it originates in the Rocky Mountain National Park in Colorado and flows into the South Platte River. Located east of the continental divide in the northern front range of Colorado, the river travels 126 miles east through Roosevelt National Park and descends over 7,000 feet. The canyon has been home to native Americans for centuries. Evidence of their presence such as: fire hearths, burial sites, tipi rings, and rock shelters have been located in the canyon.
Igneous Rocks Igneous rock is formed by the cooling and solidification of magma or lava. Igneous rocks can form below the surface as intrusive(plutonic) rocks or they can form on the surface as extrusive(volcanic) rocks.
I believe this to be an igneous rock. It has the characteristics ofbasalt. Basalt is an intrusive rock which is fine grained and typicallydark in color.
Sedimentary Rocks Sedimentary rocks are formed by the deposition of material at the Earth’s surface and within bodies of water. Sediment is produced when preexisting rocks are broken down by weathering processes. This sediment then moves by various forces such as: gravity, water, wind, and glacial ice. Over time the layers of sediment succumb to the forces of compaction and cementation to form rock.
I believe this to be a sedimentary rock. The various layers ofsediment are easily scene. The rock appears to be a dark sandstonewith rings or clay.
This appears to be heavily weathered sandstone. The rockcontains uniform sand sized grains throughout.
Metamorphic Rocks Metamorphic rocks are formed when an existing rock is subjected to intense heat and/or pressure. The parent rock of a metamorphic rock may be an igneous, sedimentary, or even a metamorphic rock. Pressure from within the Earth or tectonic processes may cause a rock to change.
I believe this to be a metamorphic rock. Gneiss is what this rocklikely is. Gneiss are medium to course grained banded rocks. I cansee this rock once had clear bands but it appears these bands havebeen broken by forces of heat and pressure.
This rock is weathered and dull in appearance, however I do believeit is a type of quartzite. Sandstone is the parent rock to quartzite.This one seems to contain iron oxide.
ReferencesNational and Wild Scenic Rivershttp://www.rivers.gov/wsr-cache-la-poudre.htmlWikipediahttp://www.wikipedia.org/Tarbuck and Lutgens, Earth: An Introduction to Physical Geology, 10 th Edition, Prentice Hall (2011),