Science Earth Terms

Rift Valley

A rift valley is a low land region that forms when 2 continental plates diverge/move apart from one other. They are created through sea floor spreading. Over a long period of time they can change into a basin. The basins can transition from a continental rift to oceanic rift over time. They are created by tectonic activity instead of erosion.

Subduction Zone

A subduction zone is where 2 plates collide and one dives/sinks below the other because of the density difference. This occurs when a oceanic and continental plate meet and the denser/thicker oceanic crusts dives underneath the less dense continental plate. Oceanic crust is more dense than continental crust which is why it sinks into the mantle. They are located around the edge of the Pacific Ocean also known as the "Ring of Fire," these subduction zones cause very strong earthquakes, tsunamis, and volcanoes.

Transform Boundary

A transform boundary occurs when 2 plates grind/slide past each other in a horizontal direction so neither plate is added to or destroyed. (Not tearing or crunching) This results in a fault which is a crack in the earths crust. This produces many earthquakes due to the jagged tectonic plate edges grinding against each other creating stress that's quickly released in the form of a earthquake. Most transform faults are found in ocean basins and connect mid ocean ridges. Volcanoes do not occur due to there not being any subduction. They are also known as a strike-slip fault.

Continental Crust

Continental Crust is made up different types of granite and is also created by plate tectonics. This type of crust is less dense than oceanic crust and so doesn't sink in subduction. It's actually thrusted up like in forming mountain in convergent plate boundaries. Continental crust is always much older than oceanic since it is rarely destroyed/recycled in subduction. (Some nearly as old as the earth itself)

Convergent Boundary

Convergent Boundary occurs when 2 or more plates move towards each other and collide. This boundary can cause mountain ranges, volcanoes, and ocean trenches. There are 3 types of convergent boundaries; continent to continent collision, continent to oceanic crust collision, and oceanic to oceanic collision.

Divergent Boundary

Divergent boundaries are where 2 plates are diverging or pulling/moving apart from each other. They produce mid ocean ridge systems & rift valleys. They also create new lithosphere and contribute to sea floor spreading due to how magma oozes to fill in the space between the plates forming a mid ocean ridge and spreads outwards forming new ocean floor & crust.

Mid Ocean Ridge

Mid ocean rides are underwater, extensive mountain ranges. They are formed by plate tectonics, uplifting the ocean floor. This creates magma due to their convection current rise in the mantle. New sea floor is created when the magma cools as divergent plates move apart.

Oceanic Crust

Oceanic crust is made up of different basalts, 3-6 km beneath the ocean floor. It is constantly being formed at mid ocean ridges where tectonic plates are diverging and magma is filling the space becoming young crust. This is why oceanic crust is much younger than continental. It can also be destroyed in subduction zones since this crust is more dense/thick than continental and so sinks into the mantle beneath the continental.

Asthenosphere

The asthenosphere is a weaker part of earths upper mantle below the lithosphere. It is made up of a soft/fragile plastic like material that is much less rigidity than the lithosphere above it. Convection currents also generate/flow here pushing magma up and creating new crust. It has temperatures ranging from 300-500 degrees Celsius.

Lithosphere

The lithosphere is the solid outer part of the earth that includes the upper most solid part of the mantle and the crust. The lithosphere is the most rigid and coolest of all the layers. There are 2 types of lithosphere, oceanic and continental.