Rocks and Roles in Earth's History

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Three Types of Rocks

The three types of rock are sedimentary, igneous, and metamorphic. Sedimentary rocks are types of rocks that are formed by the deposition of material at the Earth's surfase and within bodies of water. Sandstone and shale ar both examples of sedimentary rocks. Igneous Rocks are formed through the cooling and solidification of magma or lava. Basalt, obsidian, and granite are some examples of igneous rocks. Metamorphic rocks are from the transformation of existing rock types, in a process called metamorphism. Schist, slate, and gneiss are examples of metamorphic rocks.


The process by which materials form or are deposited in layers, as in sedimentary rocks and some igneous rocks. This is formed at the Earth's surface, as from the lava flows and volcanic fragmental deposits ( The atmosphere and the ocean also exhibit stratification,with the warmer air or water ccupying the upper layers.

Stratification in Rocks

Age of Rocks/Landforms

One way to determine the age of a landform is by looking at the fossils inside of the rocks and finding what age period those fossils are from. The age period that those fossils are from determines how old the landforms are.  Another way to measure the age of a landform is by the number of layers of rock so that when there are more layers of rock the landform will be older since more sediment had piled over time. Also, you can find the absolute age of a rock by studying nuclear decay of the radioactive isotopes in the rock.

Rock Cycle

Rock Cycle

Rock Layers

Huge layers of horizontal sedimentary rock could be tipped if there was an earthquake that would cause the tectonic plate underneath the rock to shift and cause the layer of sedimentary rock to be tipped. Older layers of rock will go above younger layers of rock if subduction occurs so that two tectonic plates will collide to cause one plate to go under the other so that the older layers of rock will be above the younger layers of rock.

Living Organisms in Landforms

Some of the ways that living organisms effect the formation of landforms is by when an animal dies and its skeleton will turn into sediment that forms the layers of rock. Another way that living organisms effect the formation of landforms is by fossils slowly turning into fossil fuels such as oil and the landform forming around the oil deposit. Also, coral islands will form from the decomposed fish skeletons and coral that cause a landform or island above the ocean.

Rock Cycle Video

By Ethan Hagmann