Dynamic Earth

Question 1

Seismic Waves

Answer 1

waves of energy that travel through the Earth’s crust, caused by earthquakes

Question 2

Continental Drift

Answer 2

movement of the plates of the Earth’s crust in relation to each other

Question 3

Pangaea

Answer 3

a super-continent that existed about 225 million years ago. All of the landmasses that existed at this time were joined together to form this super-continent.

Question 4

Panthalassa

Answer 4

the vast sea surrounding the supercontinent of Pangaea

Question 5

Plate tectonics

Answer 5

the theory concerning the movement of the continental plates

Question 6

Mantle

Answer 6

thick layer inside the Earth, below the crust. Most of the mantle is solid rock, although the upper part is molten rock called magma.

Question 7

Convection current

Answer 7

circular movement that occurs when warmer, less dense fluid particles rise and cooler, denser fluid particles sink

Question 8

Continental crust

Answer 8

circular movement that occurs when warmer, less dense fluid particles rise and cooler, denser fluid particles sink

Question 9

Oceanic crust

Answer 9

one of the types of crust that makes up the Earth’s outer layer. Oceanic crust is thinner than continental crust and made up of dense, heavy rocks such as basalt.

Question 10

Subduction

Answer 10

process in which two tectonic plates push against each other, and oceanic crust sinks below the less dense continental crust

Question 11

Destructive plate boundaries

Answer 11

a convergent boundary where two plates collide

Question 12

Constructive plate boundaries

Answer 12

plate that creates new land from cooling magma

Question 13

Ocean ridges

Answer 13

an area where the tectonic plates move apart, allowing magma from the mantle to rise, forming underwater volcanoes and creating new oceanic crust as it is cooled and solidified by sea water

Question 14

Laurasia

Answer 14

one of the two smaller continents created when the supercontinent Pangaea broke apart about 200 million years ago

Question 15

Gondwanaland

Answer 15

one of the two smaller continents created when the supercontinent Pangaea broke apart about 200 million years ago

Question 16

Hotspots

Answer 16

a localised place where an activity occurs

Question 17

Folding

Answer 17

buckling of rocks caused when rocks are under pressure from both sides

Question 18

Anticlines

Answer 18

folds that bend upwards

Question 19

Synclines

Answer 19

folds that bend downwards

Question 20

Fault

Answer 20

a break in a rock structure causing a sliding movement of the rocks along the break

Question 21

Rift Valleys

Answer 21

a sunken area where two blocks of crust have dropped down between faults

Question 22

Horst

Answer 22

a block of the Earth’s crust, with faults on either side, that has been pushed upwards by the forces below

Question 23

Slip Fault

Answer 23

a geological feature where movement along a fault is sideways—that is, where the blocks of crust slip horizontally past each other

Question 24

Volcanoes

Answer 24

natural opening in the Earth’s crust connected to areas of molten rock deep inside the crust

Question 25

Magma

Answer 25

a very hot mixture of molten rock and gases, just below the Earth’s surface, that has come from the mantle

Question 26

Lava

Answer 26

mixture of molten rock and gases that has reached the Earth’s surface from a volcano

Question 27

Volcanic bombs

Answer 27

large rock fragment that is blown out of erupting volcanoes; also known as a lava bomb

Question 28

Active

Answer 28

describes a volcano that is erupting or has recently erupted

Question 29

Extinct

Answer 29

describes a volcano that has not erupted for thousands of years and is effectively dead

Question 30

Dormant

Answer 30

describes a volcano that has not erupted for more than 20 years but is not considered extinct

Question 31

Conservative Plate Boundaries

Answer 31

when plates slide past each other in opposite directions, but without creating or destroying lithosphere. … those that link a destructive boundary with a constructive boundary.

Question 32

Tremor

Answer 32

a slight earthquake.

Question 33

Epicentre

Answer 33

the point on the earth’s surface vertically above the focus of an earthquake.

Question 34

Focus

Answer 34

the point of origin of an earthquake.

Question 35

Trilateration

Answer 35

the process of determining absolute or relative locations of points by measurement of distances, using the geometry of circles, spheres or triangles

Question 36

Seismograph

Answer 36

an instrument that measures and records details of earthquakes, such as force and duration.

Question 37

Richter Scale

Answer 37

a numerical scale for expressing the magnitude of an earthquake on the basis of seismograph oscillations. The more destructive earthquakes typically have magnitudes between about 5.5 and 8.9; it is a logarithmic scale and a difference of one represents an approximate thirtyfold difference in magnitude.

Question 38

Body wave

Answer 38

a seismic wave that moves through the interior of the earth, as opposed to surface waves that travel near the earth’s surface. P and S waves are body waves.

Question 39

Surface wave

Answer 39

A seismic wave that travels across the surface of the Earth as opposed to through it. Surface waves usually have larger amplitudes and longer wavelengths than body waves, and they travel more slowly than body waves do. Love waves and Rayleigh waves are kinds of surface waves.

Question 40

Tsunami

Answer 40

a long, high sea wave caused by an earthquake or other disturbance.

Question 41

Primary Wave

Answer 41

Primary waves are alternatingly compressional and extensional, and cause the rocks they pass through to change in volume. These waves are the fastest traveling seismic waves and can travel through solids, liquids, and gases.

Question 42

Secondary Wave

Answer 42

An earthquake wave in which rock particles vibrate at right angles to the direction of wave travel. Secondary waves can travel through solids but not through liquids.

Question 43

Love Wave

Answer 43

A type of seismic surface wave in which particles move with a side-to-side motion perpendicular to the main propagation of the earthquake. The amplitude of this motion decreases with depth. Love waves cause the rocks they pass through to change in shape.