Geology: Plate Tectonics

Plate tectonics

A theory stating that the Earth's surface is broken into plates that move

Pangaea

The most recent supercontinent, which formed over 300 million years ago and started breaking apart less than 200 million years ago.

Continental drift

Alfred Wegener's hypothesis that the continents have moved relative to each other over Earth's history

Seafloor spreading

The process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge

tectonic plates pull apart at divergent boundaries, allowing hot magma from the Earth's mantle to rise, cool, and solidify into new oceanic crust

Divergent boundary

Place where two plates are moving apart

Mid-ocean ridge

A divergent boundary between two oceanic plates

Continental rift

A divergent boundary between two continental plates

geological features formed where tectonic plates are pulled apart, causing the Earth's lithosphere to stretch and thin, eventually leading to the formation of new ocean basins

Convergent boundary

Place where two plates come together

Continental volcanic arc

Chain of volcanoes that form on continental crust where oceanic crust subducts at an ocean-continent convergent boundary

Island arc

Chain of volcanic islands that form on oceanic crust where oceanic crust subducts at an ocean-ocean convergent boundary

Subduction

A process where an oceanic plate descends below a less dense plate, causing the removal of the plate from the surface

Transform boundary

Place where two plates slide past each other, forming strike-slip faults

Ring of Fire

A major area in the basin of the Pacific Ocean where many earthquakes and volcanic eruptions occur

Partial melting

The process that occurs when only certain minerals in a rock melt, while others remain solid

Hydration melting

A type of partial melting caused by addition of water to the mantle, which lowers the melting temperature (occurs at subduction zones)

Decompression melting

A type of partial melting caused by a reduction of pressure, which lowers the melting temperature (occurs at divergent boundaries)

Rock cycle

The process of changing rocks on Earth into different forms, namely igneous, sedimentary, and metamorphic

Igneous rock

Rock formed through the cooling and solidification of magma or lava

Sedimentary rock

Rocks that are formed through sedimentary processes, including sediments lithifying and precipitation from solution

Metamorphic rock

Rocks formed through increased temperature and pressure which changes the minerals within the rock

Lithosphere

The outermost physical layer of the Earth, made of the entire crust and the top of the upper mantle; forms the tectonic plates

Asthenosphere

A ductile physical layer of the Earth, below the lithosphere; movement in the asthenosphere drives plate motion

Orogenesis

Mountain building due to the convergence of tectonic plates

Paleomagnetism

Branch of geology concerned with magnetism in rocks that was induced by the Earth's magnetic field at the time of their formation

Magnetic striping

Symmetric patterns of magnetism formed by ocean floor rocks recording changes in Earth's magnetic field