Dictionary

Igneous: Igneous rocks are formed when magma or lava cools. The process can either occur within the Earth’s crust as magma (molten rock) cools (intrusive) or on the surface of the earth where lava erupts (extrusive).

Sedimentary: Sedimentary rocks form where grains of minerals are eroded away and re-deposited in a different location. Sedimentary rocks are commonly deposited in the ocean as rivers erode the source rock and transport the minerals out to sea.

Metamorphic: Metamorphic rocks occur when either igneous or sedimentary rocks are exposed to high pressure and temperatures, and chemical processes. Exposure to such conditions changes the mineral composition, texture and and chemical composition of the rock.

Crust: Outermost, solid, layer of the Earth. Continental crust is the less dense ‘floaty’ version of crust and Oceanic crust is denser, therefore usually makes up ocean basins.

Mantle: A layer of the Earth making up about 84% of the Earth’s entire volume. The material making up the mantle is heavy in silica content and is able to flow viscously. This means that the mantle is a large driver behind plate tectonics.

Plate Tectonics: The movement of the Earth’s crust around the surface as continents. Continents may collide or drift apart from each other depending on push and pull factors determined by movement of magma in the mantle.

Subduction Margin: When two plates collide and one gets pushed underneath the other. The Himalayas are a mountain range caused by the Indian Plate subducting beneath the Eurasian Plate
Divergent Margin: When two plates drift apart from each other
Transform Margin: When two plates move beside each other, in opposite directions. This is occuring right now along the San Andreas Fault in California.

Basalt: An Igneous rock type, basalt is important because it is the type of magma that creates dense oceanic crust. Common to find along mid-ocean divergent margins.

Mineral Assemblages: The minerals that make up a rock type – rocks are defined by their mineral assemblages. Mineral Orientation is also important because mineral orientation can show if the rock was subjected to pressure during formation, and can also record the direction of magnetic north in some minerals during formation.

 

 

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