Section 2: Plate Tectonics & Geological Processes

GES 108

Geothermal Energy: Heat energy originating from within Earth’s interior.

Continental Drift: The theory proposed by Alfred Wegener in 1912 stating that Earth’s continents are constantly moving across the surface due to convection currents within the asthenosphere. Evidence for this includes matching mountain ranges and rock types, glacial deposits, and the geographic distribution of fossils.

Plate Tectonics: The modern theory that builds upon continental drift, explaining the origin, movement, and recycling of lithospheric plates and the landforms they create.

Supercontinents: Massive landmasses that form when most or all continental plates merge together.

Amasia: The predicted future supercontinent that may form in about 200 million years when Eurasia and the Americas collide.

Pangea: The most recent supercontinent, which existed about 330 million years ago, when all continents were joined together like puzzle pieces.

Rodinia: One of the earliest known supercontinents, which existed around one billion years ago.

Lithospheric Plates: Large, rigid segments of Earth’s crust that move independently over the semi-fluid asthenosphere. There are 14 major plates.

Primary Plates: The largest and most independent tectonic plates that move on their own.

Secondary Plates: Smaller plates whose movements are influenced by the motion of nearby primary plates.

Asthenosphere: The semi-fluid layer of the upper mantle beneath the lithosphere that allows tectonic plates to move due to convection.

Ridge Push: A tectonic process where rising magma at mid-ocean ridges creates new crust, pushing older crust away and driving plate movement.

Mantle Drag: The process by which convection currents within the asthenosphere pull and drag lithospheric plates along their flow patterns.

Slab Pull: A tectonic force where the dense, sinking portion of a subducting plate pulls the rest of the plate downward into the mantle, accelerating its movement.

Plate Boundaries: The zones where two or more tectonic plates meet and interact, producing earthquakes, volcanoes, and mountain ranges.

Divergent Boundary: A boundary where two plates move apart, allowing magma to rise and create new crust.

Ridge: A long, elevated mountain chain formed when magma from below the crust rises and solidifies along a divergent boundary.

Rift: A deep crack or fissure formed when the crust is stretched and split apart.

Rift Valley: A long, narrow valley formed by the downward displacement of land between parallel faults, often containing volcanic activity.

Ocean Basin: A depression formed when divergent rifting occurs underwater, allowing seawater to fill the space between separating plates.

Island Arc (Divergent Context): A chain of small volcanic islands formed when magma solidifies along diverging oceanic crust.

Convergent Boundary: A boundary where two tectonic plates collide, often resulting in subduction, earthquakes, and mountain formation.

Subduction: The process in which one tectonic plate (usually oceanic crust) moves beneath another (usually continental crust) and sinks into the mantle.

Wadati-Benioff Zone: A deep zone of earthquake activity corresponding to the subduction of an oceanic plate beneath a continental plate, such as along the west coast of South America.

Tsunami: A large, powerful ocean wave caused by undersea earthquakes, volcanic eruptions, or landslides, often resulting from subduction events.

Oceanic Crust Recycling: The process where old oceanic crust sinks into the mantle at subduction zones and new crust forms at mid-ocean ridges, keeping most oceanic crust younger than 150 million years.

Continental Arc: A chain of volcanoes formed on a continental plate above a subducting oceanic plate.

Island Arc (Convergent Context): A curved chain of volcanic islands that forms on oceanic crust above a subducting plate.

Pacific Ring of Fire: A major area encircling the Pacific Ocean characterized by frequent earthquakes, deep ocean trenches, and active volcanoes caused by subduction zones.

Collision Boundary: A type of convergent boundary where two continental plates collide, forming large mountain ranges instead of volcanoes because magma cannot reach the surface.

Mountain Range: A long chain of mountains formed when continental plates collide and crust is forced upward, as in the Himalayas.

Transform Boundary: A boundary where two tectonic plates slide horizontally past each other, creating zones of intense shearing and earthquakes.

Zone of Shearing: The region along a transform boundary where crustal plates scrape against each other, generating friction and seismic activity.

Earthquake: A sudden release of energy in Earth’s crust caused by movement along faults or plate boundaries, producing ground shaking and sometimes tsunamis.