GCSE Restless Earth Denfintions

Question 1

Volcano

Answer 1

An opening in the earth’s crust through which molten lava, ash, and gases are ejected

Question 2

Earthquake

Answer 2

A sudden movement of the earth’s crust creating seismic waves

Question 3

Plate boundary

Answer 3

The border between two adjacent lithospheric plates classified by the direction in which the plates move

Question 4

Oceanic crust

Answer 4

Lithosphere found under the oceans primarily composed of basalt; thinner but denser than continental crust ranging from 7 to10 km thick

Question 5

Continental crust

Answer 5

Lithosphere which forms the continents and the areas of shallow seabed close to their shores made primarily of granite, ranging from 25 to 75km thick

Question 6

Lithosphere

Answer 6

The outer part of the earth, consisting of the crust and upper mantle, approximately 100 km thick

Question 7

Hotspot

Answer 7

A portion of the Earth’s surface that experiences volcanism due to a rising mantle plume usually far from tectonic plate boundaries.

Question 8

Convergent plate boundary

Answer 8

A tectonic boundary where two plates collide. Plates of equal density form fold mountains; plates of unequal density form volcanoes as a result of subduction

Question 9

Divergent plate boundary

Answer 9

A tectonic boundary where two plates separate and new crust is formed

Question 10

Conservative plate boundary

Answer 10

A tectonic boundary where two plates move sideways past each other at different speeds. No volcanoes form

Question 11

Pyroclastic flow

Answer 11

A fast-moving avalanche of superheated gas, lava, ash and rock ejected explosively from a volcano with speeds of 700km an hour and temperatures of about 1,000 degrees

Question 12

Lava

Answer 12

Molten rock that reaches the earth’s surface through a volcano or fissure

Question 13

Focus

Answer 13

The point below the Earth’s surface where seismic waves originate during an earthquake. It is where the energy stored in the rock is first released

Question 14

Epicentre

Answer 14

The point on the Earth’s surface directly above the focus of an earthquake

Question 15

Plate tectonics

Answer 15

A theory that explains the global distribution of earthquakes, volcanoes, continental drift Plate tectonics and mountain building caused by the interaction of the earth’s lithospheric plates

Question 16

Mantle

Answer 16

A layer between the crust and the outer core, about 2,900km thick. Consists of magma which is viscous

Question 17

Magma

Answer 17

Molten material beneath or within the earth’s crust, from which igneous rock is formed

Question 18

Mercalli scale

Answer 18

Measures the effects of an earthquake through observational methods

Question 19

Richter scale

Answer 19

Measures the magnitude of an earthquake using seismometers and seismographs

Question 20

Magnitude

Answer 20

A measure of the strength of seismic waves

Question 21

Sesimometer

Answer 21

An instrument that measures ground movements, usually placed underground

Question 22

Seismograph

Answer 22

An instrument that displays the readings of seismometers in graphical form

Question 23

Ocean trench

Answer 23

Deep, long and narrow depressions 3-4km from the sea floor located at subduction zones

Question 24

Fold mountains

Answer 24

Mountain chains formed as a result of the collision of twotectonic plates

Question 25

Fumarole

Answer 25

An opening in the earths crust through which steam and gases pass.

Question 26

Geyser

Answer 26

An opening in the earths crust through which hot water and steam is intermittently ejected

Question 27

Seamount

Answer 27

A volcano that rises from the ocean floor but does not reach to the water’s surface

Question 28

Island arc

Answer 28

A chain of volcanic islands that have formed as a result of the convergence of two oceanic plates

Question 29

Convection current

Answer 29

The movement of molten rock in the mantle driven by temperature differences between the lower and upper mantle

Question 30

Mid-ocean ridge

Answer 30

An underwater mountain chain that is normally found along a divergent plate boundary. A rift runs along its spine where new sea floor is created