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science > The Earth > Flashcards

The Earth Flashcards

1
Q

Seismic waves

A

waves of energy that travel through the Earth’s crust, caused by earthquakes. The behave differently when passing through different materials allowing us to identify the chemical composition of the different layers.

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2
Q

Continental drift

A

movement of the plates of the Earth’s crust in relation to each other. Proposed by Alfred Wagner and stated that the earth was made up of different plates in which continents floated and moved on.

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3
Q

Pangea

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.

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4
Q

Panthallasa

A

the vast sea surrounding the supercontinent of Pangaea

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5
Q

Plate tectonics

A

the theory concerning the movement of the continental plates. The earths crust is divided in thirty plates which move on a layer of magma in the upper mantle.

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6
Q

Mantle

A

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

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7
Q

Convection current

A

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

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8
Q

Continental crust

A

the plates of the Earth’s crust that make up the land and are between 30-70 km thick.

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9
Q

Oceanic crust

A

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. Has a thickness of about 6km.

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10
Q

Subduction

A

process in which two tectonic plates push against each other, and oceanic crust sinks below the less dense continental crust. This creates powerful earthquakes and destructive volcanoes when oceanic crust meets cold sea water.

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11
Q

Destructive plate boundary

A

convergent boundary where two plates collide

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12
Q

Constructive plate

A

plate that creates new land from cooling magma

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13
Q

Ocean ridges and sea floor spreading.

A

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

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14
Q

Laurasia

A

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

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15
Q

Gondwanaland

A

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

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16
Q

Hotspots

A

localised place where an activity occurs. They are areas where the mantle is hotter causing rocks in the upper mantle to melt allowing magma to surge upwards.

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17
Q

Folding

A

buckling of rocks caused when rocks are under pressure from both sides. As the plates of the arts slowly move the solid rocks is pushed pulled bent and twisted. The forces are huge and can fold them into rolling hills and valley and can move them up down and sideways.

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18
Q

Anticlines

A

folds that bend upwards

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19
Q

Synclines

A

Folds that bend downwards

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20
Q

Fault

A

break in a rock structure causing a sliding movement of the rocks along the break. Created when tectonic plates move and fracture the rocks that make them up.

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21
Q

Rift valleys

A

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

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22
Q

Horst

A

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

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23
Q

Slip fault

A

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

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24
Q

Tremors

A

vibration on the Earth’s surface caused by an earthquake

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25
Q

Epicentre

A

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

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26
Q

Focus

A

the point at which an earthquake begins

27
Q

Triangulation

A

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

28
Q

Seismograph

A

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

29
Q

Richter scale

A

Scale that ensures the amount of energy released by an earthquake

30
Q

P waves

A

Compression waves that move through the Earth in the same way that sound waves do. They move very fast

31
Q

S waves

A

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.

32
Q

Body waves

A

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

33
Q

Tsunami

A

powerful ocean wave triggered by an undersea earthquake. When waves approach land they become shallower allowing the waves to build up to heights of 30m

34
Q

Volcano

A

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

35
Q

Magma

A

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

36
Q

Lava

A

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

37
Q

Volcanic bombs

A

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

38
Q

Active

A

describes a volcano that is erupting or has recently erupted

39
Q

Extinct

A

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

40
Q

Dormant

A

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

41
Q

Conservative plate boundary

A

Plates that in which crust is neither created nor destroyed

42
Q

evidence for continental drift

A

The main piece of evidence for the idea of Pangea and continental drift was the fact that the same fossils were found in areas on opposite sides of the globe meaning that at one point they must have been connected.

43
Q

What are the purpose fo convection currents in plate tectonics

A

Convection currents allow the plates to move slowly. The magma rises and expands towards the surface until it is cool and falls back down . The causes the plates to slowly move sideways.

44
Q

What happens when two continental plates collide

A

When two continents collide huge mountain ranges form as the crust crumbles upwards such as the Himalayas which continues to grow and the Indo-aus plate and Eurasian plate collide.

45
Q

Convergent plates

A

When two plates collide

46
Q

Sliding

A

When two neighbouring plates slide past each other earthquakes occur. More severe quakes occur when something prevents the plates from sliding causing pressure to build up in order to restart movement. These are conservative plates.

47
Q

Where does folding occur

A

Folding usually occur below the surface are exposed by erosion

48
Q

How do earthquakes occur

A

They result from movement in the earthquakes up to 700km below. These cause vibrations or tremors on the surface. Most occur at; areas where plates are subduction, spreading to form mid ocean ridges and slipping and sliding to from jolts.

49
Q

Power of earthquakes

A

The power of earthquakes depends on distance from the epicentre.

50
Q

L waves

A

Are surface waves and they they travel slower than others they travel on the surface of earth meaning that their energy is the most destructive during an earthquake

51
Q

How do volcanoes form

A

They are formed when molten rock from the mantle burst through weaknesses in the crust.

52
Q

What happens when volcanoes erupt.

A

As pressure builds up ash and steam emerge. When it erupts the lava flows from vents and fragments of rock dust ash and steam shoot out.

53
Q

Plutunic/intrusive

A

Igneous rocks formed by gradual cooling below the surface

54
Q

Volcanic extrusive

A

Igneous rock formed above the surface by rapid cooling.

55
Q

Metamorphic rock

A

Rock formed in the earth by intense pressure and heat

56
Q

Contact meta

A

Metamorphic rocks that come into contact with magma and are changed by heat.

57
Q

Regional meta

A

Rocks buried deeply and formed by pressure

58
Q

Outer Cora nad inner core

A

Made up of iron and nickel with the outer being liquid and the inner solid

59
Q

Magnetic striping and pole reversal

A

As minerals in rock form there are certain parts which point to the North Pole. However, in some cases the rocks show striping where the pole are pointing to different ways. This suggest s that the magnetic pole have reversed in the past years supporting hess’ theory of sefloor spreading

60
Q

Lithosphere

A

Top part of earth where we ;live. Is very stiff

61
Q

Asthenosphere

A

Moves Below the lithosphere and is a bit softer

62
Q

Normal fault

A

Occur when two plates move away from each other and over time one side moves down. This movement causes rocks to be horizontally offset and can impact railways, fences and water pipes

63
Q

Thrust fault

A

Occur when two plates move toward each other

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