Seafloor Spreading

Subduction

________ is the process by which the ocean floor sinks beneath a deep- ocean trench and back into the mantle;

mantle convection

The lithosphere gets shoved into the asthenosphere, the lithosphere gets melted, and becomes part of the ________ cycle.

Sea floor spreading

________ was discovered by Harry Hess in the 1960s.

Sonar

________- a device that bounces sound waves off underwater objects and then records the echoes of these sound waves.

Mid ocean ridges

________ are the longest chain of mountains in the world-- these are divergent plate boundaries.

Mariana Trench

The ________ is an example of a subduction zone.

Sea floor spreading

________ is the process that continually adds new material to the ocean floor while pushing older rocks away from the ridge.

Sonar

a device that bounces sound waves off underwater objects and then records the echoes of these sound waves

Mid ocean ridges are the longest chain of mountains in the world

- these are divergent plate boundaries

Crust

The thin, solid, outermost layer of Earth; Is either continental (landmasses) or oceanic (ocean floors)

Divergent Boundary

The boundary between two tectonic plates moving away from each other; if on land, it creates rift valleys; if on the sea floor, it creates new ocean crust and mountainous ridges.

Magma

Melted or molten rock material beneath Earth's surface; cools slowly to form rocks with larger crystals

Mid-Ocean Ridge

An underwater mountain system formed by plate tectonics; the largest single volcanic feature on Earth.

Seafloor Spreading

The formation of new areas of oceanic crust, which occurs through the upwelling of magma at mid-ocean ridges.

Subduction

The process in which a denser plate is pushed downward beneath a less dense plate when plates converge (come together)

Tectonic Plates

Huge pieces of crust that slowly move on the upper part of the mantle by convection.

Trenches

Deep and narrow depressions in the seafloor; Form where the sub-ducted plate moves into the mantle.

Convergent Boundary

Occurs when two tectonic plates move toward each other and collide.

Ocean Basin

A depression of Earth's surface in which an ocean lies

Divergent (spreading) Boundary

Where new seafloor is made and a plate "grows"

Convergent (come together) Boundary

Where plates collide

Oceanic Crust

Earth's crust below the seafloor.

Continental Crust

Crust below the continents