Unit 2 - The natural environment

Question 1

Structure of the earth

Answer 1

• 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

Question 2

Oceanic crust

Answer 2

Thin but very dense

Question 3

Continental crust

Answer 3

Thick but less dense

Question 4

4 types of plate boundaries

Answer 4

• Divergent
• Convergent
• Collision
• Transform

Question 5

Divergent plate boundary

Answer 5

• 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

Question 6

Convergent plate boundary

Answer 6

• 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

Question 7

Collision plate boundary

Answer 7

• 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

Question 8

Transform plate boundary

Answer 8

• 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

Question 9

Convection currents in the mantle

Answer 9

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

Question 10

Cause of earthquakes

Answer 10

• 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

Question 11

Focus

Answer 11

The point underground where the release of seismic energy happens

Question 12

Epicentre

Answer 12

The point above the focus on the surface of the crust

Question 13

Scales of earthquake magnitude

Answer 13

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

Question 14

Causes of volcanoes

Answer 14

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

Question 15

Features of volcanoes

Answer 15

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

Question 16

Places where volcanoes occur

Answer 16

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

Question 17

Active volcano

Answer 17

Erupts regularly

Question 18

Dormant volcano

Answer 18

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

Question 19

Extinct volcano

Answer 19

No activity detected un human history - will not erupt again

Question 20

4 types of Volcanoes

Answer 20

• Stratovolcano/composite
• Shield volcano
• Cinder cone
• Fissure vent

Question 21

Stratovolcano/composite

Answer 21

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

Question 22

Shield volcanoes

Answer 22

• 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

Question 23

Cinder cone

Answer 23

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

Question 24

Fissure vent

Answer 24

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

Question 25

Factors that increase risk and vulnerability

Answer 25

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

Question 26

Primary effects

Answer 26

Direct result of earthquakes or eruption

Question 27

Secondary effects

Answer 27

As a result of primary effects

Question 28

Primary effects of volcanic eruptions

Answer 28

• Deaths and injuries
• Crop damage
• Roads and infrastructure damage

Question 29

Secondary effects of volcanic eruptions

Answer 29

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

Question 30

Primary effects of earthquakes

Answer 30

• Deaths and injuries
• Road and infrastructure damage

Question 31

Secondary effects of earthquakes

Answer 31

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

Question 32

Causes of volcano effects

Answer 32

• Pyroclastic flow
• Lava flow
• Tephra
• Volcanic bombs
• Toxic gas cloud

Question 33

Causes of earthquake effects

Answer 33

• Collapse of buildings
• Falling objects

Question 34

Reducing risk of earthquakes

Answer 34

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

Question 35

Features of earthquake resistant buildings

Answer 35

• 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

Question 36

Predicting volcanoes

Answer 36

• 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

Question 37

Pyroclastic flow

Answer 37

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

Question 38

Lahar

Answer 38

Fast deadly mudslide made of water, mud and volcanic debris

Question 39

Opportunities of volcanoes

Answer 39

• 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