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GEOGRAPHY > Hazardous Earth > Flashcards

Hazardous Earth Flashcards

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1
Q

What are the 3 main parts that make up Earth?

A

Core, mantle and crust.

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2
Q

What is the asthenosphere?

A

The semi-molten layer that forms the top part of the mantle.

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3
Q

What is the lithosphere?

A

The layer found between the crust and asthenosphere that breaks up into tectonic plates.

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4
Q

What separates the mantle and crust?

A

the Mohorovičić discontinuity, also known as ‘Moho’.

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5
Q

The 2 types of plates are called…

A

Continental and oceanic.

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6
Q

Properties of oceanic crust?

A

Thin, made from basalt, density - 3.0kg/m3, SIMA.

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7
Q

Properties of continental crust?

A

Thick, made from granite, density - 2.6-2.7kg/m3, SIAL.

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8
Q

The 3 theories for tectonic plate movement?

A

Convection currents, slab PULL & ridge PUSH.

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9
Q

Why is continental fit weak evidence for continental drift?

A

Coasts of continents have been exposed to geomorphological processes (eg. erosion).

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10
Q

What is palaeomagnetism?

A

The idea that the magnetic poles switch and metal minerals in rocks change alignment - magma will cool in the direction of the magnetic north pole.

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11
Q

What happens at the 3 different plate boundaries?

A

Convergent - collide.
Divergent - move away.
Conservative - slide past each other.

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12
Q

What happens at convection currents?

A

Decay in core heats mantle, magma rises and spread to asthenosphere and sinks = friction in crust.

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13
Q

What happens during ridge push?

A

Magma rises through the crust, cools and forms underwater. Dense mountains slide away from each other (gravity).

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14
Q

What happens during slab pull?

A

Oceanic plate subducts into hot mantle due to gravity.

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15
Q

The 3 different plate boundaries found at convergent plate boundaries…

A

Oceanic-continental = fold mountains
Oceanic-oceanic = island arcs
Continental-continental = mountains

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16
Q

What are the 2 categories of eruptions?

A

Explosive and effusive.

17
Q

Features of composite/strata volcanoes…

A

Found mainly at convergent plate boundaries.
Steep.
Explosive eruptions.
Have long periods of inactivity.
Erupt gases, ash, lava bombs.
Acidic lava type of rhyolite and andesite.
55% SiO2 (silica) - more viscous.

18
Q

Features of shield volcanoes…

A

Found mainly at divergent plate boundaries.
Shallow.
Effusive eruptions.
More frequent eruptions that last for longer periods.
Erupt gases and lava flows.
Runny lava type of basalt.
45% SiO2 (silica) - less viscous.

19
Q

The six types of volcanic eruptions…

A

Icelandic (the least violent), Hawaiian, Strombolian, Vulcanian, Vesuvian, Plinian (the most violent).

20
Q

The seven hazards that can be caused by volcanic eruptions…

A

Lava Flows, Pyroclastic Flows, Tephra, Tsunamis, Toxic Gases, Lahars, Flooding.

21
Q

Why do volcanoes erupt?

A

As magma collects within the magma chamber, pressure increases and causes fractures, where the magma will be released through a volcanic eruption.

22
Q

How has the Hawaiian chain of islands been formed?

A

Formed at a hotspot. Basalt accumulation on the ocean floor caused the islands to move from the hotspot and become extinct.

23
Q

What is VEI and how is it calculated?

A

Volcanic Explositivity Index - calculated using magnitude and intensity (can only be used for explosive volcanoes).

24
Q

What are earthquakes?

A

A release of stress that has built up in the Earth’s crust due to tension, compression, shearing of rocks.

25
Q

Where is the epicentre?

A

Above the earthquake focus at the Earth’s surface.

26
Q

Where are earthquakes mostly concentrated?

A

Mid-ocean ridges, ocean trenches/island arcs, collision zones, conservative plate boundaries.

27
Q

Features of a P (primary) wave…

A

Fast-travelling.
Low frequency.
Vibrate in the direction of travel.
Travel through Earth’s interior (solids + liquids).
Cause least amount of damage.

28
Q

Features of a S (secondary) wave…

A

1/2 of P-wave speed.
High frequency.
Vibrates at right angles to direction of travel.
Can’t pass through liquids.

29
Q

Features of a L (love/surface) wave…

A

Slowest.
Low frequency.
Rolling vertical movement and right angles to direction of movement.
Displaces crust.
Travel through outer crust only.

30
Q

Features of a deep focus earthquake…

A

70-700 km deep.
Extremely high temperatures.
Minerals change type and volume of deep focus.
Occur at subduction zones, and are measured on Moment Magnitude Scale.

31
Q

Features of a shallow focus earthquake…

A

Around 70 km.
Occur in cold, brittle rocks from fractured rocks and stress of crust.
Release low levels of energy.

32
Q

Pro and con of Richter Scale…

A

+ Has no upper limit and represents 30-fold increase in release of energy.
- Doesn’t show impacts on people and can’t express physical movement of the crust.

33
Q

Pro and con of Modified Mercalli Scale…

A

+ Qualitative assessment, based on observation/description.
- Damage caused may not represent the earthquake’s overall strength. Many people will have different opinions of the destruction that occurred.

34
Q

Pro and con of Moment Magnitude Scale…

A

+ Uses physical movement and energy equivalents.
- Can’t be used to measure small earthquakes.

35
Q

The four hazards that can be caused by earthquakes…

A

Groundshaking, Liquefaction, Landslides/Avalanches, Tsunamis.

36
Q

What is ‘modifying the event?’

A

Mitigating hazards generated from the tectonic activities.

37
Q

What is ‘modifying vulnerability?’

A

Reducing how vulnerable people are when exposed to a tectonic event.

38
Q

What is ‘modifying loss?’

A

Reducing loss of life and damage to properties after the tectonic event.

GEOGRAPHY (9 decks)

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