4 Plate Tectonics Free Online FlashCards

What is a tectonic plate?

A tectonic plate is a moving slab of lithosphere: rigid crust and the strong uppermost mantle beneath it.

How do continents move across Earth?

Continents are embedded in moving plates, so they travel with those plates rather than plowing independently through ocean floor.

What happens at a divergent plate boundary?

At a divergent boundary, plates move apart. Magma rises and cools to form new crust, especially at mid-ocean ridges.

What is ridge push?

Ridge push is gravity-driven sliding of oceanic lithosphere away from an elevated mid-ocean ridge as it cools and becomes denser.

How does seafloor spreading renew oceanic crust?

Seafloor spreading adds new oceanic crust at mid-ocean ridges, moving older seafloor away; older oceanic lithosphere is recycled at many subduction zones.

How does ocean-floor rock age vary with distance from a ridge?

Oceanic rocks are youngest near a mid-ocean ridge and generally become older farther away, supporting seafloor spreading.

What evidence supported Wegener's idea of continental drift?

Wegener supported continental drift with clues including the fit of some continental margins and similarities in rocks, fossils, and ancient climates across separated continents.

What lies beneath tectonic plates and allows slow movement?

Plates move over the hotter, weaker asthenosphere, which can flow slowly over geologic time.

What is subduction?

At a convergent boundary, dense oceanic lithosphere can sink beneath another plate; this process is called subduction.

What can happen when two continental plates converge?

When two continents converge, their buoyant crust resists sinking and is compressed and uplifted into mountains.

How do plates move at a transform boundary?

At a transform boundary, plates slide horizontally past one another, so crust is neither created nor consumed. The San Andreas Fault is an example.

What is slab pull?

Slab pull occurs when the weight of old, cold, dense oceanic lithosphere sinking into the mantle pulls the rest of its plate behind it.