Key Words-Tectonics

Question 1

Sea Floor Spreading

Answer 1

A process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge.

Question 2

Continental Drift

Answer 2

The Earth’s continents have moved over geologic time relative to each other, thus appearing to have “drifted” across the ocean bed.

Question 3

Palaeomagnetism

Answer 3

Magnetic rock reveals a pattern of spreading away from the centre, away from the Atlantic Ocean.

Question 4

Slab Pull

Answer 4

Older, cooler plate sink at subduction zones because as they cool, they become more dense than the underlying mantle. The cooler sinking plate plus the rest of the warmer plate along behind it.

Question 5

Ridge Push

Answer 5

Newly formed plates at oceanic ridges are warm, and so have a higher elevation at the oceanic ridge than the colder, more dense plate material further away ; gravity causes the higher -plate at the ridge to push away the lithosphere that lies further from the ridge.

Question 6

Mantle Convection

Answer 6

The slow creeping motion of Earth’s solid silicate mantle as convection currents carry heat from the interior to the planet’s surface.

Question 7

Subduction

Answer 7

As two plates move towards each other, one slides into the mantle in a subduction zone. The denser plate slides under the less dense plate.

Question 8

Low Velocity Zone

Answer 8

Occurs close to the boundary between the lithosphere and the asthenosphere in the upper mantle

Question 9

Subduction Zone

Answer 9

Where two of the planet’s tectonic plates collide and one dives, or subducts, beneath the other.

Question 10

Gravitational Sliding

Answer 10

Constructive margins have elevated altitudes because of the rising heat between them, which creates a ‘slope’ down which oceanic plates slide. This occurs at destructive margins.

Question 11

Plumes

Answer 11

Magma plumes are areas of hot, upwelling mantle