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Physical Geography > 9.1 Hazards resulting from tectonic processes > Flashcards

9.1 Hazards resulting from tectonic processes Flashcards

1
Q

What is a hazard?

A

A threat that could injure people or damage the built environment.

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2
Q

What is a hazard event?

A

The occurrence or realisation of a hazard and its effects.

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3
Q

What is a disaster?

A

A hazard that causes so much damage and injury that help is needed to recover.

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4
Q

What is risk?

A

The probability of a hazard causing harmful consequences.

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5
Q

What is resilience?

A

How well a population recovers from disaster.

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6
Q

What is soil liquefaction?

A

When weak rocks act as a liquid and flow, due to ground shaking. Leads to the sinking of buildings. It occurs when groundwater is near the surface and soft sediment mixes with water.

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7
Q

What are tsunamis?

A

High, long period waves in the ocean, resulting from a sudden displacement of the seabed along a fault. They have long wavelengths so are hard to monitor.

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8
Q

What are primary earthquake hazards?

A

Shaking - sends out P, S and surface waves.

Surface faulting

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9
Q

What is a hotspot?

A

Volcanoes which sit above isolated plumes of rising magma. A jet of hot material rises from deep within the magma.

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10
Q

What is partial melting?

A

When some minerals melt before others, altering the composition of molten rock.

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11
Q

Why does viscous magma create more explosive volcanoes?

A

In fluid magma, bubbles rise to the surface.

In viscous magma, gases are trapped so pressure is built up more.

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12
Q

What is a mantle plume?

A

Stationary area of hot mantle which rises. The plume is narrow but the top spreads out under the plate to form a bulbous head.

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13
Q

What is seismic tomography?

A

An ‘x-ray’ of the earth to give an image of areas where shock waves pass through slowly or quickly.

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14
Q

What is a seismometer?

A

Records the elastic vibrations of seismic waves and creates a graph called a seismogram.

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15
Q

What is the richter scale?

A

10 point logarithmic scale

Measures the height of the largest wave.

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16
Q

What are the advantages of the richter scale?

A

Easy comparison of EQ magnitudes.

Highly accurate of magnitudes less than 4.

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17
Q

What are the disadvantages of the richter scale?

A

Relative measure - compares one size of EQ to another.

Becomes inaccurate at large magnitudes.

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18
Q

What is the moment magnitude scale?

A

Uses elements of Richter scale. Logarithmic.

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19
Q

What are the advantages of the MM scale?

A

Independent of recording instruments. Highly accurate for EQs above magnitude 4.

20
Q

What are the disadvantages of the MM scale?

A

Not accurate for EQs with magnitude less than 4.

Takes longer to determine.

21
Q

What is the Mercalli scale?

A

A 12 point scale that measures the intensity of the event and the physical damage it creates.
Very subjective.

22
Q

What is the focus?

A

The point of origin of an EQ underground.

23
Q

What is the epicentre?

A

Point on the earth’s surface that is directly above the focus.

24
Q

What is sheer stress?

A

When pressure and stress build up as the plates are forced to try to move.

25
Q

What is a P wave?

A

A primary body wave that travels underground and arrives at the detector first. Its waves are longitudinal and push-compressional.

26
Q

What are S waves?

A

Secondary body waves that travel underground. These waves are transverse, several times larger than P waves, and arrive at the detector second.
They travel through material by shearing or changing its shape in the direction perpendicular to the direction of travel.

27
Q

What is a love wave?

A

A surface wave. It has horizontal movement and a long wavelength.

28
Q

What are surface waves?

A

Waves that travel just below the surface. They move more slowly than body waves, but are often the more destructive type of wave.

29
Q

What is a Raleigh wave?

A

A surface wave with rolling vertical movement. Very destructive.

30
Q

What are seismic waves?

A

Waves of elastic energy.

31
Q

What is an Icelandic eruption?

A

Fluid basalts issue quietly from fissures at mid-ocean ridges.

32
Q

What is a Hawaiian eruption?

A

Fluid basalts issue from vaults and volcanoes. Gases escape easily and quietly with occasional gas spurts.

33
Q

What is a strombolian eruption?

A

Less fluid lava and gases escape with moderate explosions. Lava bombs.

34
Q

What is a Vulcanian eruption?

A

More violent eruptions as more viscous lava solidify quickly and trap gases. Ashes and cinders emitted.

35
Q

What is a Vesuvian eruption?

A

Viscous magma gains high gas content during long inactivity. Violent eruptions send wide ash cloud.

36
Q

What is a Plinian eruption?

A

Very violent explosion of gas, ash and pumice. Results in narrower cloud.

37
Q

What is a Pelean eruption?

A

Highly viscous magma and long inactivity cause an explosion out of weakness in the side of the volcano. Top gets blocked due to dormancy and solidification.

38
Q

What is Aa?

A

Thick but fast basaltic lava, formed when a lot of lava erupts quickly. Surface breaks into rough clinkers as it moves. Moves with sudden surges of speed, destroying anything it touches.

39
Q

What is Pahoehoe?

A

Slow flowing lava, formed when low volumes are ejected more slowly. Solidifies while moving and flows further than aa lava.

40
Q

What is a nuee ardente?

A

A very hot, incandescent cloud composed of gas and tiny fragments of solid material. Moves rapidly down slopes.
Categorised by their ashes which glow in the dark.
Caused when viscous magma causes a solid plug to grow in the vent of a volcano so that lava has to explode sideways out of a weakness if the flank of the volcano.

41
Q

What is pyroclastic material?

A

Solid particles that reach the ground in pyroclastic falls.

42
Q

What is tephra?

A

Airborne pyroclastic material.

43
Q

Give the names for the different types of solid material in size order.

A

Ashes, cinders, lapilli, volcanic blocks

44
Q

What are volcanic bombs?

A

Round fragments of solid lava, formed as molten lava cools while spinning through the air.

45
Q

What are pyroclastic flows?

A

When hot, dry rock fragments and gases move rapidly away from the vent down slopes by gravity. Very dense.

46
Q

What are lahars?

A

Volcanic mudflows.

Physical Geography (17 decks)

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