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Hazardous Earth > Key words > Flashcards

Key words Flashcards

1
Q

Lithosphere

A

The section of Earth’s profile which includes the crust and upper (solid) mantle

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2
Q

Asthenosphere

A

The uppermost part of the mantle roughly 80-200 km beneath the Earth’s surface. This is the layer than tectonic plates rest and move.
Below the lithosphere

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3
Q

Plate tectonics theory

A

Theory that the crust is divided up into smaller sections which all float on top of the mantle, and all move

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4
Q

Sea-floor spreading

A

Process by which oceanic plates split apart and new crust is formed through the rising of basaltic magma

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5
Q

Convection currents

A

Material in the mantle rises up and down. Hot material, which is less dense, moves upwards. As it cools, density increases and it sinks once again

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6
Q

Ridge push (gravitational sliding)

A

Secondary form of plate movement, caused by the heavy weight of new oceanic crust at ocean trenches
As the crust moves away from a mid-ocean ridge, it cools and becomes denser and thicker. This causes the lithosphere to slope away from the ridge and gravity pulls the lithosphere down this slope, pushing it forwards.

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7
Q

Slab pull

A

Process by which dense and old oceanic crust is pulled down under less dense continental crust at subduction zones
The pulling force exerted by a cold, dense oceanic plate plunging into the mantle due to its own weight. The theory is that because the oceanic plate is denser than the hotter mantle beneath it, this contrast in density causes the plate to sink into the mantle

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8
Q

Convergent boundary

A

Land is destroyed as two plates collide. The denser (oceanic) plate is forced (subducted) below the lighter plate and melted in the mantle

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9
Q

Divergent boundary

A

Two plates pull apart creating new land- ocean ridges or rift valleys (constructive)

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10
Q

Conservative boundary

A

Plates move past each other, but no land is destroyed. Pressure builds and is suddenly released, often as powerful earthquakes

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11
Q

Magma plume

A

Upward flow of hotter magma, than the surrounding mantle

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12
Q

Young fold mountains

A

Mountains made of thick accumulations of sedimentary rock which form along the edges of continents where two plates collide e.g. the Himalayas

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13
Q

Rift valley

A

Narrow depression between an upland area on each side, sometimes seen at divergent plate boundaries as the two plates pull apart

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14
Q

Ocean ridge

A

Area of raised seabed, where the two tectonic plates are spread apart at a divergent plate boundary

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15
Q

deep-sea trench

A

Deep depression found along the seaward edge of convergent plate boundaries.
Trenches are formed through subduction, which occurs when tectonic plates collide and push one plate beneath the other. Trenches can be found all over the surface floor of the ocean at subduction zones

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16
Q

Island arc

A

Often crescent shaped line of volcanoes protruding from the ocean along a convergent plate boundary

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17
Q

Plate boundary

A

The boundary between two tectonic plates

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18
Q

Hotspot

A

Site of a volcano away from a plate boundary as hot magma rises and melts through the crust

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19
Q

Shield volcano

A

Landform with a central vent and gently sloping sides, built up by layers of basaltic lava flows e.g. Mauna Load, Hawaii

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20
Q

Composite volcano

A

Steep-sided, pyramid-shaped landform built up from alternating layers of ash and lava flows e.g. Mount Vesuvius, Italy

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21
Q

High-viscosity magma

A

Underground material that is very sticky and silica rich e.g rhyolite and andesite, formed from melted crust at convergent boundaries

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22
Q

Low-viscosity magma

A

Underground material that flows relatively freely, with low silica content e.g. basaltic, often formed of mantle material, not melted crust

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23
Q

Effusive eruption

A

Low-magnitude volcanic ejection, such as runny basaltic lava which flows away from a vent- little height of ejecta is maintained

24
Q

Explosive eruption

A

Violent ejection of volcanic material due to a great build-up of pressure, trapped gases and viscous magma often at a convergent plate boundary

25
Q

Super volcano

A

Volcano capable of the largest type of eruption- 1,000km^3 or more of material is erupted

26
Q

Volcanic Explosivity Index (VEI)

A

Classification of volcanoes based on the volume of material ejected, the eruption height and duration of the eruption

27
Q

Pyroclastic flows

A

A mixture of volcanic rock, ash and gases, heated to upwards of 800degrees C which flows rapidly downslope, sometimes at 700km/h

28
Q

Lahar

A

Volcanic mudflow composed of pyroclastic material and water which flows down a volcano and along a river channel

29
Q

Tephra

A

Generic name for material ejected from a volcano; can be subdivided into size, from largest- volcanic bombs, to smallest-ash

30
Q

Volcanic gases

A

Sulphur dioxide and carbon dioxide and others ejected from a volcano

31
Q

Jokulhlaups

A

Glacial outburst flood caused by a heating or volcanic eruption below ice, releasing water from a subglacial lake

32
Q

Tsunami

A

High wave at the shore with potentially devastating consequences. Undersea earthquakes, volcanoes and landslides are triggers

33
Q

Focus

A

The point within earth’s crust from which a sudden pressure release occurs

34
Q

Epicentre

A

The point on Earth’s surface above the focus where an earthquake originated

35
Q

Benioff zone

A

Part of the subduction zone where the descending oceanic crust begins to melt into magma. The increased heat and friction at the region create a zone of earthquake hypocentres

36
Q

Seismic wave

A

Pressure oscillation propagating through the ground, as energy is released via an earthquake

37
Q

Shallow-focus

A

Earthquake with a focus depth of 0-70km

38
Q

Deep-focus

A

Earthquake with a focus depth of 300-700km

39
Q

Intermediate focus

A

Earthquake with a focus depth of 70-300km

40
Q

Magnitude

A

The amount of energy, for example, delivered by a seismic event

41
Q

Seismometer

A

Device used to measure earthquakes- the movement of the ground

42
Q

Moment magnitude scale

A

Scale of the amount of energy (magnitude) derived from an earthquake, a replacement of the Richter scale.
It is the main scale now used by seismologists
Includes additional parameters (size of fault rupture and rock strength)
Each increase on the magnitude scale represents a 10-fold increase in shaking and a 32-fold increase in energy released.

43
Q

Modified Mercalli scale

A

A 12 point scale which measures the impact of an earthquake.
Measures intensity, based on qualitative data
Ranges from level 1 (detected by instruments not felt by people) to Level XII

44
Q

Escarpment

A

Differential land height along a fault line caused by horizontal and movement; for example a high ridge remaining after an adjacent fall down

45
Q

Primary hazard

A

Damage and danger caused by the direct shaking of the ground
Includes ground shaking, liquefaction, landslides and avalanches

46
Q

Secondary hazard

A

Damage caused after the earthquake as a result of ground shaking
Includes tsunamis and flooding

47
Q

Liquefaction

A

Saturated or partially saturated sediments (such as soil) lose mechanical strength during an earthquake and act like a fluid

48
Q

Perception

A

The way that a person sees hazard risk- dependant on personal experience and circumstances

49
Q

Mitigation

A

Reducing the effects of a disaster- such as building strong earthquake resistant buildings

50
Q

Adaptation

A

Coping with the effects of a tectonic hazard and changing the way of life after the event

51
Q

Planning

A

Preparation for an event- covering responses to immediately spring into action as soon as a disaster occurs in order to deal with the event as quickly as possible

52
Q

Hazard risk equation

A

Risk=hazard likeliness x level of vulnerability

53
Q

Park model

A

Graph displaying the speed and magnitude at which quality of life declines after a hazard and the speed and level of recovery afterwards

54
Q

Viscosity

A

How well a substance flows. More viscous material is thicker and flows less easily

55
Q

Caldera

A

A basin-shaped depression, 2-50km in diameter formed by the collapse of a volcano following a highly explosive eruption

56
Q

Lava plateaux

A

Flat, elevated landforms created by extremely large volume effusive eruptions called flood basalts

57
Q

Richter Scale

A

Assesses energy release using maximum amplitude of seismic waves recorded on a seismogram.

Hazardous Earth (11 decks)

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