Plate tectonics key terms

Question 1

Crust

Answer 1

The outer most layer of the Earth, with two types:
a thin layer of dense basalt (oceanic)
a thicker layer of dense granite rock (continental)

Question 2

Mantle

Answer 2

The thickest layer of the Earth, made up of (semi) molten rocks with iron and magnesium. At a depth between 100-700km, the mantle becomes hotter and more fluid, known as the asthenosphere

Question 3

Core

Answer 3

The innermost part of the Earth, split into the inner and outer core, containing rocks made of iron and nickel alloys. The inner core is solid, while the outer core is molten at over 5000C

Question 4

Primordial heat

Answer 4

Heat left over from the Earth’s formation

Question 5

Radiogenic heat

Answer 5

Heat given from the decay of radioactive isotopes

Question 6

Lithosphere

Answer 6

The crust and the rigid mantle, divided into 7 large continental and oceanic plates

Question 7

Asthenosphere

Answer 7

Part of the Earth’s mantle that lies below the lithosphere at depths between 100-700 km

Question 8

Plate tectonic theory

Answer 8

The theory that states that the Earth’s crust is made up of several rigid plates moving relative to one another

Question 9

Sea floor spreading

Answer 9

The theory that the ocean floor is moving away from the mid oceanic ridge and across the deep ocean basin, to disappear beneath continents and ocean arcs

Question 10

Paleo-magnetism

Answer 10

A record of the history of the Earth’s magnetic field, preserved in magnetic minerals in volcanics rocks

Question 11

Subduction

Answer 11

The sideways and downward movement of the edge of the plate of the Earth’s crust into the mantle beneath another plate

Question 12

Constructive plate boundary

Answer 12

A plate margin where new crust is generated as the plates pull away form each other (found at mid ocean ridges)

Question 13

Destructive plate boundary

Answer 13

A plate margin where crust is destroyed as two plates converge (associated with island arcs or young fold mountains)

Question 14

Conservative plate boundary

Answer 14

A plate margin where two tectonic plates are moving past each other with no addition or destruction of plate material

Question 15

Deep sea trenches

Answer 15

Prominent, long, narrow topographic depressions of the ocean floor. Typically 50-100km wide and 3-4km deeper than the surrounding ocean floor

Question 16

Island arcs

Answer 16

A curved chain of volcanic islands located at a tectonic plate margin, typically with a deep ocean on the convex side

Question 17

Yound fold mountains

Answer 17

Mountains formed when two tectonic plates are pushed together

Question 18

Volcano

Answer 18

A mountain or hill, typically conical, having a crater or vent through which lava, rock fragments, hot vapour and gas are or have been erupted from the Earth’s crust

Question 19

Ridge push

Answer 19

A proposed driving force for plate motion in plate tectonics that occurs at midocean ridges as the result of the rigid lithosphere sliding down the hot, raised asthenosphere below

Question 20

Gravitational sliding

Answer 20

Another name for ridge push

Question 21

Slab pull

Answer 21

A geophysical mechanism whereby the cooling and subsequent densifying of a subducting plate produces a downward force along the rest of the plate

Question 22

Ocean ridges

Answer 22

A seafloor mountain system formed by plate tectonics

Question 23

Rift valleys

Answer 23

A steep sided valley formed by the downward displacement of a block of the Earth’s surface between the nearly parallel faults or fault systems

Question 24

Horst

Answer 24

A raised or elongated block of the Earth’s crust lying between two faults

Question 25

Wegner's theory of continental drift

Answer 25

Wegner believed that all continents once orgininated from one large continent, Pangea, 300 milion years ago. Pangea then split into two continents, Laurasia and Gondwanaland, which further drifted into the continents we have today