Unit 2 - The natural environment Flashcards

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1
Q

Structure of the earth

A
  • Crust - 100km thick - oceanic & continental crust
  • upper mantle - 400km deep 100-1300˚C
  • Lower mantle - 700km deep 200-2500˚C
  • Outer core - 2900km deep 2500-3000˚C
  • Inner core - 5150km deep 4000-5000˚C
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2
Q

Oceanic crust

A

Thin but very dense

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3
Q

Continental crust

A

Thick but less dense

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4
Q

4 types of plate boundaries

A
  • Divergent
  • Convergent
  • Collision
  • Transform
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5
Q

Divergent plate boundary

A
  • Two plates move apart
  • Magma rises and fills gap - erupts as Laval and solidifies to make new crust
  • Also known as a constructive boundary
  • Example: Mid-Atlantic ridge - North American and Eurasian plate
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6
Q

Convergent plate boundary

A
  • Plates move towards each other
  • When continental and oceanic plates come together - denser oceanic sinks and continental rises - forms subduction zone
  • Friction between plates and the mantle melts oceanic crust
  • Magma rises and erupts as a volcano
  • Also known as a destructive boundary
  • volcanoes and earthquakes occur
  • Example: Nazca plate subjects under South American plate
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7
Q

Collision plate boundary

A
  • When two continental plates of similar densities move towards each other
  • Crust pushed up and forms fold mountains
  • Only earthquakes occur
  • Example: Himalayas growing with Indian & Eurasian plate
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8
Q

Transform plate boundary

A
  • Plates move pas each other in opposite directions or in same direction at different speeds
  • Also known as a conservative boundary
  • Volcanoes and earthquakes occur
  • Example: San Andreas Fault - USA
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9
Q

Convection currents in the mantle

A

Hotter less dense material due to outer core rises and colder denser material sinks

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10
Q

Cause of earthquakes

A
  • Convection currents cause movement of plates
  • Plates can get stuck and build up pressure
  • When pressure is too high the boundary suddenly moves
  • All stored energy is released in seismic waves
  • Waves move through the crust and cause shaking
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11
Q

Focus

A

The point underground where the release of seismic energy happens

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12
Q

Epicentre

A

The point above the focus on the surface of the crust

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13
Q

Scales of earthquake magnitude

A
  • Richter scale - energy released
  • Moment magnitude scale - distance the fault line has moves
  • Mercalli scale - visible damage
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14
Q

Causes of volcanoes

A
  • Formed when ruptures on the crust allow lava, volcanic ash and hot gases to erupt
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15
Q

Features of volcanoes

A
  • Magma chamber
  • Layers of ash and lava
  • vent
  • Crater
  • Lava flow
  • Ash cloud
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16
Q

Places where volcanoes occur

A
  • Divergent plate boundaries
  • Convergent plate boundaries
  • Hot-spots - areas of super-heated plumes of magma under the crust
17
Q

Active volcano

A

Erupts regularly

18
Q

Dormant volcano

A

Potential to become active, gap of eruptions from less than a year to over 10000

19
Q

Extinct volcano

A

No activity detected un human history - will not erupt again

20
Q

4 types of Volcanoes

A
  • Stratovolcano/composite
  • Shield volcano
  • Cinder cone
  • Fissure vent
21
Q

Stratovolcano/composite

A
  • Forms at convergent boundaries
  • Erupts violently and unpredictably
  • Lava is thick and slow moving
  • Steep sides and classic cone shape
22
Q

Shield volcanoes

A
  • Forms at divergent boundaries and hot-spots
  • Eruptions are less explosive and more predictable
  • Lava is runny and flows for long distances
  • Gently sloping sides
23
Q

Cinder cone

A
  • Hot lava and ash blasts into the air
  • Substances cool, fall and stick to the cone’s slope as opposed to flowing
24
Q

Fissure vent

A
  • Linear volcanic cent where lava erupts
  • Often few meters wide and kilometers long
25
Q

Factors that increase risk and vulnerability

A
  • Urbanization - densely populated areas with less robust buildings increases vulnerability
  • Economic development - LEDCs have poorer infrastructure, planning, preparation, healthcare, systems and emergency responses
26
Q

Primary effects

A

Direct result of earthquakes or eruption

27
Q

Secondary effects

A

As a result of primary effects

28
Q

Primary effects of volcanic eruptions

A
  • Deaths and injuries
  • Crop damage
  • Roads and infrastructure damage
29
Q

Secondary effects of volcanic eruptions

A
  • Spread of disease
  • Homelessness
  • Shortage of resources
  • Loss of jobs and businesses
  • Transport difficulties
  • Tsunamis
  • Mudflow
  • Fires
30
Q

Primary effects of earthquakes

A
  • Deaths and injuries
  • Road and infrastructure damage
31
Q

Secondary effects of earthquakes

A
  • Spread of disease
  • Homelessness
  • Shortage of resources
  • Loss of jobs and businesses
  • Tsunami
  • Landslides
  • Fires
32
Q

Causes of volcano effects

A
  • Pyroclastic flow
  • Lava flow
  • Tephra
  • Volcanic bombs
  • Toxic gas cloud
33
Q

Causes of earthquake effects

A
  • Collapse of buildings
  • Falling objects
34
Q

Reducing risk of earthquakes

A
  • Earthquake resistant buildings
  • Education - drills, practice and planning
  • Hazar mapping - identify areas of high risk
35
Q

Features of earthquake resistant buildings

A
  • Reinforced elevator shaft
  • Automatic shutters to prevent glass falling
  • Fire-resistant materials
  • Deep foundations
  • Rubber shock absorbers in foundation
  • Flexible joints for building to move
  • Interlocking steel frame
  • Counterweights on roof for vibrations
36
Q

Predicting volcanoes

A
  • Seismometers - detect tremors in ground before eruption
  • Tiltometer - detect changes in angle of slope - magma chamber grows
  • Gases - gases released in increasing quantities before eruption e.g. CO2
  • Satellite observation - hot areas detected under earth’s surface
  • Helicopter observation - aerial perspective can show danger under the surface
  • Volcano’s history - frequency and violence of previous eruptions
  • Volcanologist - people skilled at predicting volcanoes
37
Q

Pyroclastic flow

A

Mixture of ash, pumice and hot gases that flows down a volcano

38
Q

Lahar

A

Fast deadly mudslide made of water, mud and volcanic debris

39
Q

Opportunities of volcanoes

A
  • Fertile soil - high in magnesium and potassium
  • Popular attraction - good for tourism industry
  • Rare metals - gold, copper, zinc, silver, rubies and diamonds
  • Geothermal energy - heat from rising magma