All three types of rock—igneous, sedimentary, and metamorphic--are found in Northern California. Igneous rock is formed from molten rock under the earth. If igneous rock is formed under the ground, it is called plutonic. If it comes to the surface it is called volcanic. The Sierra Nevadas are primary igneous—a mixture of both exposed plutonic and volcanic.
Sedimentary rock is layered rock formed usually underwater as either turbidite flows or materials precipitating or settling out of water. The Great Valley Sequence is an example of sedimentary rock. Upturned portions of the Great Valley Sequence are observed throughout the Coast Range mountains, including at Monticello Dam.
Metamorphic rock is either igneous or sedimentary rock which has undergone a change due to high pressure and/or temperature. The Francision shale is an example of metamorphic rock formed as a result of tetonic interaction between the continental and ocean plates and is found throughout the Coast Range mountains.
All of the tasks for this earthcache can be safely completed from the pulloff, without crossing the road. If you would like to learn more about the geology discussed in this earthcache, or need help on answering the below questions, check out the “Resources and References” section below. Be sure to send me the answers to the following questions through my geocaching.com profile, and please wait to log a find on this earthcache until via e-mail I confirm that your answers are correct.
OTHERWISE I WILL HAVE TO DELETE YOUR LOG!!
Enjoy and have fun visiting and learning about this awesome location! This earthcache is wheelchair-accessible. 
Questions:
1. What is the name of the formation of sedimentary rock observed in the roadcut at Monticello Dam?
2. What evidence is there that this formation is sedimentary in nature?
3. What is structural orientation of the strata at this location?
4. What was the structural orientation of this strata originally?
5. What is the difference between a formation and sequence, as used in geology?
6. Is this formation mostly carbonate or silicate?
Resources and References:
http://nrs.ucdavis.edu/stebbins/natural/geology/geo_report.htm
http://bioregion.ucdavis.edu/book/06_Monticello_Dam/06_03_moores_geo_gvs.html
http://science.kqed.org/quest/2012/01/26/geological-outings-around-the-bay-mount-vaca-and-the-monticello-dam/
http://en.wikipedia.org/wiki/Monticello_Dam
http://en.wikipedia.org/wiki/Igneous_rock
http://en.wikipedia.org/wiki/Sedimentary_rock
http://en.wikipedia.org/wiki/Metamorphic_rock
http://en.wikipedia.org/wiki/Rock_(geology)