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Geography > Restless Earth > Flashcards

Restless Earth Flashcards

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1
Q

What is the core?

A

The centre of the our planet.

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2
Q

What is the outer core?

A

Fluid and mostly made of iron and nickel.

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3
Q

What is the inner core?

A

Solid.

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4
Q

What is the mantle?

A

Composed of very hot, dense rock.
Almost 3,000km thick.
Accounts for 84% of Earth’s mass.

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5
Q

What are the characteristics of oceanic crust?

A

Very dense (heavy). Mean density 3,000kg/m3.
Thin, 5-10km.
Can sink easily into mantle.
Easily destroyed.
Young crustal material.

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6
Q

What are the characteristics of continental crust?

A

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

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7
Q

What makes the plates move?

A

Convection currents with mantle move heated rock upwards from core towards crust. It cools and sinks back to core, where the cycle starts over.

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8
Q

How do constructive plates work?

A

The Eurasian and North American plates being pulled apart, moving them away from one another. Movement causes regular, but weak earthquake activity. Magma wells up,from mantle to plug gap so often gentle volcanic activity. This rising of material pushes up crust slightly at either side of plate margin, creating a mid-oceanic ridge.
Also found where continental plate is splitting apart and rift valleys are seen.

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9
Q

How do destructive plate margins work?

A

Have subduction zone where oceanic crustal material is pulled into mantle, where it melts and is destroyed.

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10
Q

Describe an oceanic-continental crust margin.

A

Plates moving towards each other.
Oceanic plate is denser so is forced underneath as they move together.
Called subduction zone.
Oceanic plate melts to form magma and earthquakes are triggered. Melts due to friction and heat from mantle.
Magma collects to form magma chamber, which then rises through cracks in continentals crust.
As pressure builds up, volcanic eruption may occur causing composite cone volcanoes.
At point where plate is forced down, an oceanic trench forms as deep gap in sea is created.

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11
Q

How do form mountains form?

A

Due to pressure from colliding plates, which causes continental crust to crumple.

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12
Q

Describe an oceanic-oceanic crust margin?

A

As oceanic crust sinks into mantle, it melts and creates less dense material than surrounding rock.
Deep ocean trench forms where more dense material pushed down into mantle and can be very deep.
No fold mountains as no continental crust to buckle upwards.
Magma rises and may erupt through crust to create volcanic island. A chain or arc of such can be formed and are aligned to boundary of where plates moving towards each other.

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13
Q

What is an example of an oceanic-continental crust margin?

A

South American-Nazca plate margin.

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14
Q

Describe a continental-continental crust margin?

A

Meet at collision zone.
Crusts of both buckle and fold upwards.
Two sets of fold mountains overthrust one another, creating large range of high mountains.
Little material melting, and what does melt cannot rise through high mountains so no volcanoes. Instead forms large intrusions into mountain range, called batholiths.
Magma cools slowly to form granite cores to mountain.

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15
Q

Wha it’s an example of a continental-continental crust margin?

A

Himalayas and Andes ranges.

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16
Q

Describe processes and landforms at conservative margins.

A

Two plates try to slide past one another.
Friction causes plates to stick, pressure builds up.
Pressure eventually released as earthquake when plates move suddenly.
Crust neither created or destroyed so no volcanic eruptions.

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17
Q

What is an example of a conservative margin?

A

San Andreas fault line.

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18
Q

What are the 3 basic rock types?

A

Igneous.
Sedimentary.
Metamorphic.

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19
Q

How do igneous rocks form?

A

If magma gets above surface, called lava, cools quickly, making tiny crystals. Known as extrusive igneous rock. Basalt made this way.

If magma cools underground, cools slowly, making large crystals. Known as intrusive igneous rock. Granite made this way.

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20
Q

How do sedimentary rocks form?

A

Small particles of rock or dead plants and animals deposited under sea as sediment, builds up over in layers. Squeezed and turned into rock. Limestone made from dead sea creatures. Sandstone made from sand particles.

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21
Q

How do metamorphic rocks form?

A

Other rocks changed by heat or pressure. Limestone under pressure turns to marble, mudstone heated turns to slate.

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22
Q

What are the characteristics of basalt?

A

Dark grey/black.
Glittery speckles.
Igneous.

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23
Q

What are the characteristics of granite?

A

Speckled grey, white, black, pink.
Very hard, large crystals visible.
Igneous.

24
Q

What are the characteristics of limestone?

A

Grey, white or yellow.
May have fossils, fizzes when a drop of acid is added.
Sedimentary.

25
Q

What are the characteristics of sandstone?

A

Yellow/orange.
Often see grains of sand, May rub off.
Sedimentary.

26
Q

What are the characteristics of slate?

A

Dark grey.
Layers split apart easily, smooth, can be marked.
Metamorphic.

27
Q

What are the characteristics of marble?

A

White, swirls of colour.
Can be highly polished for fireplaces and floors.
Metamorphic.

28
Q

How do earthquakes occur?

A

Along plate margins.
Plates move past, towards or away from each other.
Movement not smooth so friction causes plates to get stuck.
Pressure builds up.
Earthquake occurs when pressure released.

29
Q

Where do earthquakes occur?

A

At plate margins where friction occurs and stresses build up as sections of crust move past each other. Stronger earthquakes happen at destructive and conservative margins.

30
Q

Name places where earthquakes occur.

A

Around Pacific Ocean.
Roughly in north-south line in middle of Atlantic Ocean.
Roughly in east-west line across shorthorn Europe, Himalayas and south-east Asia.

31
Q

What is the focus?

A

Point where earthquake starts.
Energy waves race rapidly from point.

32
Q

What is the epicentre?

A

Point at ground level, directly above the focus, where the shockwaves are felt first.

33
Q

How are earthquakes measured?

A

Seismograph records shockwaves from earthquake.
Magnitude of earthquake measured on Richter Scale.

34
Q

What damage would a magnitude 3 earthquake cause?

A

Just felt by people sitting still.

35
Q

What damage would be caused by a magnitude 5 earthquake?

A

Damage poorly constructed buildings.

36
Q

What damage would be caused by a magnitude 9 earthquake?

A

Near total destruction.

37
Q

What type of scale is the Richter scale?

A

Log scale.

38
Q

What is liquefaction?

A

When rock or soil contains water is shaken by earthquake.
Water rises to surface and turns soil to liquid mud.
Any building resting on this sink into mud and collapses.

39
Q

What is a tsunami?

A

Large wave of seawater caused by earthquake.
Shock waves from plate movement create small waves (30cm high) in ocean surface.
As move towards shore, come into shallower seawater, become larger (up to 30m high).

40
Q

What are the stages of a tsunami?

A
  1. Plate shifts abruptly, causing earthquake, displacing water.
  2. Waves generated and move out in all directions across ocean, some travelling as fast as 600mph.
  3. As waves enter shallow water, compress, speed slows, and build in height.
  4. Wave height increases, associated currents intensify, becoming threat to life and property.
41
Q

What are the signs of a tsunami?

A

Dramatic fall in sea level from shore, exposing areas normally underwater.

42
Q

When and where was the Indian Ocean earthquake?

A

26 December 2004.
Magnitude 9.2.
Off west coast of Sumatra, Indonesia, in Indian Ocean.

43
Q

What were the causes of the Indian Ocean earthquake?

A

Fault line exists where Indo-Australian plate pulled (sub ducted) under Sunda plate, which lies on southern edge of Eurasian plate.
Sudden slip of 15m along 1600km section of fault p, lifting seafloor several metres and triggering tsunami.

44
Q

What were the short term impacts on people?

A

66% Sri Lanka’s fishing boats destroyed.
At least 125,000 people injured.
1.1 million people left homeless.

45
Q

What were the long term impacts on people of the Indian Ocean earthquake?

A

187,000 people dead, 43,000 missing.
17 low-lying Maldives islands freshwater supplies contaminated, uninhabitable for decades.
Emotional distress of losing relatives, no body found.
Rebel group GAM declared ceasefire with Indonesian government and singed peace agreement in 2005.

46
Q

What were the short term impacts on the environment of the Indian Ocean earthquake?

A

30m high tsunami from epicentre to all countries around Indian Ocean.

47
Q

What were the long term impacts on the environment of the Indian Ocean earthquake?

A

Damage to coral and mangrove ecosystems on coasts.
Worldwide rises in sea level of 0.1mm as water spilled out from Indian Ocean after seafloor raised.

48
Q

What was the preparation for the Indian Ocean earthquake?

A

No official warning system in place.
One island evacuated to higher ground.
10 year old girl in Phuket, Thailand on holiday saw water receding and warned parents, beach evacuated, saving about 100 lives.

49
Q

What were the immediate and long term responses to the Indian Ocean earthquake?

A

International aid and expertise from around world - over US $7 billion.
State of emergency delcared in Sri Lanka, Indonesia and Maldives to allow distribution of aid.
Indian Ocean Tsunami Waring System set up by UNESCO, 25 new seismograph stations to detect future tsunamis and warn countries in region via national tsunami information centres.
Community-bases centres set up - evacuation areas, food and water supplies, and search and rescue plans.

50
Q

What are the 3 types of volcanoes?

A

Shield volcanoes, composite volcanoes and super volcanoes.

51
Q

What are shield volcanoes?

A

Large, wide, cone-shaped.
Have gentle slopes as made from runny (basic) lava flows that hardened on top of each other.

52
Q

What are composite volcanoes?

A

Classic mountain-shaped where cone made up from hardened layers of ash and lava created after eruption.
Occur at destructive plate boundaries.
High cone, main and secondary vents.

53
Q

What are supervolcanoes?

A

Create wide depressions called calderas, with ridge of high land encircling them.
Forms when volcano erupts so violently it collapses in on itself, covering magma chamber under layers of rock. Magma and pressure build up over time, ending in violent eruption which can disrupt whole world.
E.g. Campi Flegrei.

54
Q

Name a supervolcano.

A

Yellowstone supervolcano, Yellowstone National Park, Wyoming, USA.

55
Q

What are the impacts of Yellowstone supervolcano on people?

A

Everyone killed within 1,000km - inhaling ash, creating concrete-like substance in lungs could kill approx. 90,000.
Many buildings destroyed by 30cm of ash. As far as Los Angeles and Chicago.
Vehicle filters clogged by ash - air and road travel severely disrupted.
Water supplies undrinkable.
Usual global rainfall and temp patterns upset, cause harvests to fail and famines around world.

56
Q

What are the impacts of Yellowstone volcano on the environment?

A

Global climate change for at least 6 to 10 years, reducing average temp by 10oC due to sulfureic aerosols in atmosphere.
All mammals in Yellowstone Park Likely to die, including bison and wolves, disrupting local ecosystem for many years.
Monsoon rains in Asia May fail, drought conditions.

Geography (5 decks)

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