Tectonic Plate Boundaries and Associated Phenomena

Vocabulary flashcards covering key terms from the lecture on tectonic plate boundaries, associated geologic processes, and related features such as subduction zones, hotspots, and earthquake distribution.

Tectonic Plate

A rigid segment of Earth’s lithosphere that moves slowly over the asthenosphere.

Plate Boundary

The region where two tectonic plates meet and interact through divergence, convergence, or lateral sliding.

Divergent Boundary

A plate margin where two plates move apart, allowing magma to rise and create new crust.

Convergent Boundary

A plate margin where two plates move toward each other, leading to subduction or continental collision.

Transform Boundary

A plate margin where plates slide horizontally past one another, often producing earthquakes.

Spreading Ridge (Ocean Ridge)

An underwater mountain chain formed at a divergent boundary where new oceanic crust is created.

Continental Rift

A divergent boundary within a continent that forms a linear valley, e.g., the African Rift Valley.

Mantle Convection Cell

Circulating flow of mantle material that drives plate motion by rising and sinking due to temperature differences.

Mantle Plume

A column of hot mantle rock rising from deep within Earth, potentially feeding hotspot volcanism.

Hotspot

A long-lived zone of volcanic activity fed by a mantle plume, independent of plate boundaries.

Subduction Zone

A convergent boundary where dense oceanic lithosphere sinks beneath another plate into the mantle.

Subducting Slab

The descending portion of oceanic lithosphere in a subduction zone.

Mantle Wedge

Mantle material above a subducting slab that partially melts when hydrated, generating magma.

Rift Valley

A linear depression formed by continental rifting; the East African Rift is a prime example.

Mid-Atlantic Ridge

A major oceanic spreading ridge running down the center of the Atlantic Ocean.

Iceland

An island straddling the Mid-Atlantic Ridge where a divergent boundary and mantle plume create intense volcanism.

Continent-Continent Collision

Convergent interaction of two continental plates, producing large mountain belts.

Himalayas

Mountain range formed by the collision of the Indian and Eurasian plates.

Mountain Range

A series of connected mountains formed chiefly by tectonic processes such as continental collision.

Continent-Ocean Collision

Convergence where oceanic lithosphere subducts beneath continental lithosphere, generating volcanic arcs.

Andes

South American mountain belt formed by subduction of the Nazca Plate beneath the South American Plate.

Ocean-Ocean Collision

Convergence of two oceanic plates where one subducts beneath the other, forming trenches and island arcs.

Trench

A deep, narrow depression in the ocean floor created by subduction.

Mariana Trench

The world’s deepest ocean trench (≈11 km) formed by Pacific Plate subduction beneath the Mariana Plate.

Pacific Ring of Fire

A horseshoe-shaped zone of frequent earthquakes and volcanism encircling the Pacific Ocean margins.

Lithosphere

The rigid outer shell of Earth, comprising crust and uppermost mantle, forming tectonic plates.

Asthenosphere

The ductile, partially molten layer beneath the lithosphere on which plates move.

Deep Focus Earthquake

An earthquake occurring at depths greater than ~300 km, typically within subducting slabs.

Earthquake

A sudden ground shaking caused by abrupt release of energy along faults, often at plate boundaries.

Volcano

A vent or opening through which molten rock, ash, and gases erupt, commonly at plate margins or hotspots.

Oceanic Crust

Thin, dense crust forming the ocean floor, mainly basaltic in composition.

Continental Crust

Thick, buoyant crust composing Earth’s continents, primarily granitic in composition.

Oceanic Lithosphere

Oceanic crust plus the underlying upper mantle portion that behaves as a rigid plate.

Transform Fault (San Andreas Fault)

A major strike-slip fault in California marking the transform boundary between the Pacific and North American plates.

Volcanic Island Chain

A line of progressively older volcanic islands formed as a plate moves over a stationary hotspot.