1. Natural Hazards

Question 1

What is a natural hazard?

Answer 1

A natural hazard is a natural event with a large social impact

Question 2

What are 6 factors affecting hazard risk?

Answer 2

• population
• urbanisation and pop density
• frequency and magnitude
• level of development
• prediction
• human activities

Question 3

What is the structure of the earth?

Answer 3

• Inner core (1400km in diameter) - solid made of iron and nickel at 5500 degrees
• Outer Core - 2100 km thick, semi-solid , temp around 5250
• Mantle - 2900 km thick, semi molten, less dense than the outer core
• Crust - oceanic and continental 2 types

Question 4

What are the 2 types of crusts?

Answer 4

• oceanic crust - thinner (5-10km) but is more dense and heavier
• continetal crust (older than oceanic as does not subduct) - 25-90 km, thicker but lighter and less dense

Question 5

What is the slab-pull theory?

Answer 5

• the movement of plates is due to the subduction of oceanic plates into the mantle and dragging the rest of the plate with it

Question 6

Where do earthquakes occur?

Answer 6

• on all plate boundaries
• mainly around the pacific ring of fire

Question 7

Where do volcanoes form?

Answer 7

• at constructive or destructive margins
• can also form at hotspots (where columns of magma escape through the crust of the earth)

Question 8

What takes place at a constructive plate boundary and what is an example?

Answer 8

• at a constructive plate boundary the plates move apart
• e.g Mid Atlantic Ridge
• make broad and flat shield volcanos
• as magma break through overlying crust shockwaves create earthquakes

Question 9

What happens at a destructive plate boundary and what is an example?
(continental and oceanic)

Answer 9

• at a destructive plate boundary plates collide into each other
• when oceanic (Nazca) and continental collide (South American) collide, the oceanic subducts under the continental as it is more dense
• friction causes earthquakes and the melting of the oceanic plate makes magma which breaks through to make a steep sided composite volcano (violent and explosive)

Question 10

What happens at a destructive plate boundary (continental and continetal)

Answer 10

• there is no subduction inside 2 plates collide and crust becomes crumpled and uplifts
• causes fold mountains such as Himalayas and formations of mountains cause earthquakes
• no volcanos

Question 11

What takes place at a conservative plate boundary and what is an example?

Answer 11

• 2 plates move past each other in opposite directions or the same direction but at diff speeds
• only earthquakes take place due to the friction
• no volcanos
• San Andreas Fault

Question 12

What are primary hazards of volcanic eruptions?

Answer 12

• ash
• pyroclastic flow (superheated material travels up to 500 km/h)
• lava flow
• gas emissions (sulfur dioxide, CO2 and water)
• volcanic bombs (rocks ejected by volcano)

Question 13

What are secondary hazards of volcanic eruptions?

Answer 13

• Lahars (water mixes with ash to create fast mudflow)
• Acidification (sulphur mixes with water to increase acidity of water)
• Landslides
• Climate Change
• Fires
• Floods

Question 14

What are primary effects of earthquakes?

Answer 14

• ground shaking
• gas emissions

Question 15

What are secondary effects of earthquakes?

Answer 15

• building collapse
• landslides
• gas leaks
• fires
• soil liquefaction
• subsidence (shrinking of the earths surface)
• mudflows
• tsunami

Question 16

What is some general infomation about Nepal?