SLO3

Major Rock Types

The 3 Main Rock Types

Much knowledge about life has came from fossils and then published for the rest of the world to catch up. Fossils show us evidence of things such as footprints and physicality's of what was here before us and how evolution progressed. Fossils can be found in a sedimentary rock at the most preserved levels. The three main rock types are: igneous, metamorphic and sedimentary. Throughout earths history the same three rocks recycle into other types of rocks in a process known as the "rock cycle" (The Interactive Geology Project, 2022).

Igneous Rock

Igneous is formed by the cooling of molten rock at either surface which is lava, or underground as other rocks. The heat of the molten rock does not preserve organisms but with the exception of tree trunks surrounded by the lava form rare casts.

Metamorphic Rock

Metamorphic is formed when existing rock is transformed under high heat with pressure that destroys any fossils in the rock prior to its metamorphism.

Sedimentary Rock

Sedimentary forms with the accumulation of minerals plus other materials. Rocks at the core are broken down, a process called 'weathering'. Sediments are moved by water and wind that are deposited in other layers. Overtime the sediments build up and solidify to become sedimentary rocks. Organs can be preserved the best in the layers.

Permineralization Preservation

usually happens with bone and wood with tiny pore spaces
groundwater seeps through minerals deposit through
minerals crystalize, hardening and preserving the organisms

Trace Fossils

traces of marks left by organisms
evidence of the organism but not the actual organism itself
fine grained
footprints
found in places with water like swamps, lakes, floodplains

Weathering process

-mechanical (warm), physical (cold)

Chemical Process

-change in chemistry form different rocks

Rounding Process

-shape, transport distance

Sorting Process

-environment of where the rock came from

Deposition

-sediments pile up on land

Lithification

-compact and cementation

LA JOLLA CAVES

I recently visited the La Jolla caves in San Diego, Ca tying into our rock objective. For the geology aspect of these caves they just so happen to be made of fractured sandstones and mudstones. Sandstone is a clastic sedimentary rock made of sandy silica grains. It makes up almost 25% of all rocks. Most sandstone is compromised of quartz or feldspar and happen to be the most resistant minerals in the weathering process. The other component of this cave is the mudstone sedimentary rock that forms where clay has settled in calm waters such as lakes or deep sea. Lastly, over the years of the sandstone slowly eroding by the weather the creation of these caves have been created and have been a tourist attraction for non-locals to visit!

Earle, S. (2015). Physical Geology. Victoria, B.C.: BCcampus. Retrieved from https://opentextbc.ca/geology/

Geology background. Museum of Natural History. (2020, December 18). Retrieved November 3, 2022, from http://www.colorado.edu/cumuseum/programs/schools-and-groups/fossils-classroom/materials-and-resources/geology-background#:~:text=Mudstone,%20shale,%20and%20limestone%20are,are%20found%20at%20the%20top

Ballard, Michael F. “San Diego Geology – Sea Caves.” Southern California Regional Rocks and Roads, 28 Nov. 2016, https://www.socalregion.com/geology/san-diego-geology/sea-caves/#:~:text=The%20sea%20caves%20at%20La,%2C%20stalactites%2C%20and%20stalagmites%20exist.

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