The Restless Earth Flashcards

1
Q

What are the 4 layers of the earth?

A

Crust (solid)
Mantle (mostly solid)
Outer core (liquid)
Inner core (solid)

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2
Q

What are the two types of crust?
What are their differences?

A

Oceanic.
Very dense (mean density is 3000kg/m3)
Thin 5-10km
Can sink into mantle
Easily destroyed
Young crustal material

Continental.
Less dense (mean density is 2,700kg/m3)
Thick 30-70km
Does not sink easily into the mantle
Hard to destroy
Old crustal material

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3
Q

What are the 13 tectonic plates?
(Use a diagram)

A

1 North American plate
2 Pacific plate
3 Nazca plate
4 South American plate
5 Cocos plate
6 Caribbean plate
7 African plate
8 Eurasian plate
9 Arabian plate
10 Indian plate
11 Australian plate
12 Philippine plate
13 Antarctica plate

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4
Q

What makes plates move?

A

Convection currents

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5
Q

What is Pangea?

A

250 million years ago, a supercontinent slowly broke up and drifted apart creating the continents as we know them today.

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6
Q

What are the four main types of plate margins?

A

Constructive
Destructive (oceanic + continental or oceanic + oceanic)
Collision
Conservative

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7
Q

What happens at a constructive plate boundary?

A

Plates are pushed apart, so they move away from one another and new crust is created. Magma wells up from the mantle to plug the gap, so there is often frequent volcanic activity here. This movement causes regular, but weak earthquake activity.

The rising of material pushes up the crust slightly at either side of a plate margin, thus creating a mid-oceanic ridge

Mid Atlantic ridge (in the Atlantic Ocean). Here, the North American and Eurasian plates are being pulled apart, moving away from one another.

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8
Q

What happens at a destructive plate boundary? (Oceanic + continental)?

A

Where an oceanic plate crashes into a continental plate and the oceanic crust is pushed into the mantle and destroyed. This movement is not smooth, because of the friction between the rough surfaces. The plates may become stuck until pressure is suddenly released, causing an earthquake.

When the heavy oceanic crust is pushed downwards into the mantle it creates a deep ocean trench.

Peru-Chile trench - this has been created where the Nazca plate (oceanic crust) is disappearing below the South American plate.

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9
Q

What happens at a destructive plate boundary? (Oceanic + oceanic)?

A

Where an oceanic plate crashes into another oceanic plate. As the oceanic crust sinks into the mantle it melts and creates a less dense material than the surrounding rock.

When the heavy oceanic crust is pushed downwards into the mantle it creates a deep ocean trench. Magma may also rise up and erupt through the crust to create an arc of volcanic islands.

Mariana ocean trench in the Pacific Ocean.

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10
Q

What happens at a collision plate boundary?

A

Two sections of continental crust crash into each other. The crusts both plates buckle and fold upwards

When the continental plates collide, fold mountains are formed (as both plates are the same density). The two sets of mountains overthrust one another, creating a large range of high mountains.

Himalayas and the Andes

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11
Q

What happens at a conservative plate boundary?

A

Plates slide past each other. Crust is neither created or destroyed. When friction causes the two plates to sick, pressure to move builds up. This pressure is eventually released as an earthquake when the plate move suddenly.

No landforms. As crust is neither creates nor destroyed at conservative margins, there are no volcanic eruptions.

San Andreas fault in California.

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12
Q

What are the shield volcano characteristics?

A

Large, wide, cone shaped volcanos with gentle slopes. Made from layers of runny lava flows.

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13
Q

Give some examples of shield volcanos

A

Mauna kea in Hawaii

Galápagos Islands.

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14
Q

What are the characteristics of a composite volcano?

A

Tall, mountain shaped volcanos made of hardened ash and lava. Often have multiple vents.

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15
Q

Give some examples of composite volcanos.

A

Helka in Iceland

Mt St Helans in USA

Mt Kilimanjaro in Tasmania.

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16
Q

What are the characteristics of a super volcano.

A

Create wide depressions called calderas.

Calderas form when A volcano erupts so violently it collapses in on itself.

Magma and pressure build up over time, causing a bulge to form in the land and creating an eruption that could disrupt the entire planet.

1000km3 of material must be erupted during explosion to be classed as a super volcano.

17
Q

Give an example of a super volcano.

A

Yellowstone national park.

18
Q

What would be some impacts on people if a super volcano erupted.

A

Everyone within 1000km would be killed.

90,000 may die from inhaling ash, which forms a cement like mixture in the lungs.

Many buildings would be destroyed- only takes 30cm of dry ash to cause a roof to collapse.

Water supplies would be undrinkable.

Ash would clog air filters on all vehicles, transport would be disrupted for weeks.

19
Q

What would be some impacts on the environment if a super volcano erupted.

A

2000 million tonnes of sulphur would enter the atmosphere, forming sulphuric acid that would cloak the earth in 2-3 weeks, cooling the planet.

Global temperatures could drop by up to 10 degrees Celsius.

67 mammal species would die, disrupting the ecosystem for decades.

It could take 10 years for vegetation to Reestablish.

20
Q

What is a tectonic plate?

A

A large segment of the earths crust.

21
Q

What is subduction?

A

The process of one plate being pushed under another.

22
Q

What are some types of rock?

A

Igneous (e.g. basalt and granite)
Sedimentary (e.g limestone and sandstone)
Metamorphic (e.g slate and marble)

23
Q

What is liquefaction?

A

When an earthquake shakes wet soil, liquid rises to the surface and turns the ground to mud.

24
Q

What is the Richter scale?

A

Units seismographs use to measure earthquakes.

Ranges between 0-10
Each point on the scale 10 times the magnitude of the previous

25
Q

What is a seismograph?

A

A piece of equipment used to detect earthquakes and measure their strength.

26
Q

When did an earthquake strike Tohoku, Japan?

A

March 11 2011

27
Q

Where did the Tohoku earthquake fall an the Richter scale?

A

9.0

It’s epicentre was 43 miles east of Tohoku at a depth of 20 miles.

It creates a tsunami that reached heights of over 40 metres.

28
Q

What plates were involved in the Tohoku earthquake?

A

Pacific was being subducted under Eurasian

29
Q

What were the short term impacts of the Tohoku earthquake on people?

A

15,894 people died, 6,152 were injured, 130,927 were displaced and 2,562 remain missing.

332,395 buildings were damaged. 300 hospitals were damaged and 11 were totally destroyed.

A 9m high wave flooded the generators of nuclear plants. People lost power immediately. 4.4 million households experienced blackouts.

30
Q

What were the short term impacts of the Tohoku earthquake on the environment?

A

Tsunami of up to 40m devastated towns and brought pollution up to 6 miles inland.

Some coastal areas experienced land subsidence as the earthquakes dropped the beachfront by over 50cm.

31
Q

What were the long term impacts of Tohoku on people?

A

The earthquake cost $235 billion US

Damage caused by the earthquake caused the meltdown of 7 reactors, causing radiation at one point to reach over 8 times normal levels.

Transport network suffered huge disruptions.

32
Q

What were the long term impacts of the Tohoku earthquake on the environment?

A

The pacific plate shifted eastwards by between 20 and 40m

Liquefaction occured on areas of reclaimed land.

The earthquake moved the earths axis by between 10 and 25cm, shortening the day by 1.8 microseconds

33
Q

What is the focus of an earthquake?

A

The point underground where the earthquake originates, from which the shockwaves spread from.

34
Q

What is the epicentre of an earthquake.

A

The point on the surface directly above the focus, where the shockwaves are strongest.

35
Q

How did Japan prepare for earthquakes?

A

Earthquake and tsunami drills take place every year on September 1st.

Buildings made earthquake resistant through non-shattering glass, weights on buildings that counter the sway and shock absorbers in foundations

Has a tsunami warning system and a complicated network of seismographs.

36
Q

What were the immediate responses to the earthquake in Tohuku?

A

Army helped to build emergency shelters quickly for the 300,000 left homeless.

Field hospitals set up and doctors and nurses flown in from other parts of the country. Many patients flown out of the emergency area for treatment.

Rescue services and army moved quickly to create access paths and clear roads.

37
Q

What were the long term responses to the earthquake in Tohuku.

A

Original 12m tsunami barriers increased to 18m. Though scientists say this would not help.

Government set up a Reconstruction Design Council who has a budget of over 23 trillion Yen to rebuild houses.