Chapter 8: Dynamic Earth

Question 1

Plate tectonics

Answer 1

the theory concerning the movement of the continental plates

Question 2

Mantle

Answer 2

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 3

Convection currents

Answer 3

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

Question 4

Continental Crust

Answer 4

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

Question 5

Oceanic Crust

Answer 5

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 6

Subduction

Answer 6

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 7

Destructive plate boundaries

Answer 7

a convergent boundary where two plates collide

Question 8

Constructive plate boundaries

Answer 8

plate that creates new land from cooling magma

Question 9

Ocean ridges

Answer 9

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 10

Conservative plate boundaries

Answer 10

Solid crust is neither created nor destroyed at these boundaries. The San Andreas Fault is perhaps the best known example of a boundary between sliding plates.

Question 11

Laurasia

Answer 11

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

Question 12

Gondwanaland

Answer 12

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

Question 13

Hotspots

Answer 13

regions in the crust where rocks in the upper mantle melt and magma surges upwards into the crust. Hotspots occur within plates. The active volcanoes in the Hawaiian Islands are caused by hotspots. The old volcanoes of Australia are also the result of hotspots.

Question 14

Folding

Answer 14

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

Question 15

Anticlines

Answer 15

folds that bend upwards

Question 16

Synclines

Answer 16

folds that bend downwards

Question 17

Fault

Answer 17

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

Question 18

Rift Valleys

Answer 18

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

Question 19

Horst

Answer 19

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

Question 20

Slip fault:

Answer 20

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

Question 21

Tremors

Answer 21

vibration on the Earth’s surface caused by an earthquake

Question 22

Epicentre

Answer 22

the point on the Earth’s centre directly above the site where an earthquake originates

Question 23

Focus

Answer 23

the point at which an earthquake begins

Question 24

Triangulation

Answer 24

finding a location by using at least three different sources of detection

Question 25

Seismograph

Answer 25

an instrument used to detect and measure the intensity of an earthquake

Question 26

Richter scale

Answer 26

a scale that measures the amount of energy released during an earthquake

Question 27

P-waves/Primary waves

Answer 27

compression waves that move through the Earth in the same way that sound waves move through air

Question 28

S-waves/Secondary waves

Answer 28

the second set of waves to be detected after P-waves. During seismic activity, secondary waves or S-waves travel in the form of transverse waves.

Question 29

Surface waves

Answer 29

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.

Question 30

Body Waves

Answer 30

waves that travel through the interior of the Earth; P-waves and S-waves are said to be body waves

Question 31

Tsunamis

Answer 31

a powerful ocean wave triggered by an undersea earth movement

Question 32

Volcano

Answer 32

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

Question 33

Magma

Answer 33

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

Question 34

Lava

Answer 34

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

Question 35

Active Volcanoes

Answer 35

describes a volcano that is erupting or has recently erupted

Question 36

Extinct Volcanoes

Answer 36

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

Question 37

Dormant Volcanoes

Answer 37

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

Question 38

Seismic waves

Answer 38

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

Question 39

Continental Drift

Answer 39

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

Question 40

Pangea

Answer 40

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 41

Panthalassa

Answer 41

the vast sea surrounding the supercontinent of Pangaea