Chapter 9: Plate Tectonic Vocabulary Flashcards

Front

Continental drift

Back

A hypothesis that originally proposed that the continents had once been joined to form a single supercontinent; The supercontinent broke into pieces, which drifted into their present-day positions.

Front

Pangaea

Back

The proposed supercontinent that 200 million years ago began to break apart and form the present landmasses.

Front

Sonar

Back

An electronic depth-sounding mechanism. Sonar is an acronym for sound navigation and ranging. Sonar calculates ocean depth by recording the time it takes for an energy pulse to reach the ocean floor and return.

Front

Deep-ocean trench

Back

A surface feature in the seafloor produced by the descending plate during subduction.

Front

Mid-ocean ridge

Back

A continuous elevated zone on the floor of all the major ocean basins and varying in width from 1000-4000 kilometers. The rifts at the crests of ridges represent divergent plate boundaries.

Front

Rift valley

Back

Deep faulted structure found along the axes of divergent plate boundaries. Rift valleys can develop on the seafloor or on land.

Front

Sea-floor spreading

Back

The process by which plate tectonics produces new oceanic lithosphere at the ocean ridges.

Front

Subduction

Back

The process by which oceanic crust sinks beneath a trench and back into the mantle at a colliding plate boundary.

Front

Paleomagnetism

Back

The study of changes in Earth’s magnetic field, as shown by patterns of magnetism in rocks that have formed over time.

Front

Plate

Back

One of numerous rigid sections of the lithosphere that moves as a unit over material of the asthenosphere.