Geological Natural Disasters

Question 1

What earthquakes occur at divergent plate boundaries?

Answer 1

• Shallow focus that is 10-70km in depth.

Question 2

What earthquakes occur at Convergent zones with subduction

Answer 2

• Denser plate subducts under less dense plate
• Shallow, medium and deep focus that is 0-700km in depth as the subducting plate can reach the asthenosphere and melt

Question 3

Convergent zones with no subduction

Answer 3

• Two continental plates collide and produce mountain ranges, faults and folds
• Shallow focus that is 0-20km in depth

Question 4

Collapsing structures

Answer 4

• As the ground moves in a series of sideway oscillations due to L-waves and R- waves, this energy is transferred to anything attached to Earth and eventually transforms into shearing forces that tear structures apart
• In effect, buildings fracture as the ground heaves, causing them to collapse

Question 5

What is tsunami

Answer 5

Tsunamis are waves that propagate from the source of the earthquake, and occur when the displacement of the seafloor subsequently displaces the water above it

Question 6

Tsunami impact

Answer 6

Tsunamis cause flooding, the collapse of buildings, uproot trees and kill people and animals

Question 7

What is Liquefaction

Answer 7

Liquefaction is when the ground shakes unconsolidated or water saturated soil

Question 8

Liquefaction formation

Answer 8

• The vibrations and shaking from the earthquake’s waves cause particles in the sub-soil to lose contact with one another
• As a result, the soil loses its rigidity and structural stability, making it temporarily act like a liquid

Question 9

Liquefaction impact

Answer 9

Liquefaction destroys power lines, causes landslides and the collapse of buildings

Question 10

Lahars (as a result of explosive eruptions)

Answer 10

A lahar is a type of flooding that originates from pyroclastic flows, which is a dense, fluidised mixture of hot gases, fine ash and rock fragments

Question 11

Lahars formation

Answer 11

Lahars are created when fast flowing water mixes with the gases, ash and rock fragments, creating a cement-like consistency

Question 12

Where does Lahars come from

Answer 12

This water comes from lakes displaced by volcanic material, melted snow or heavy rain

Question 13

Lahars impact

Answer 13

Lahars uproot trees and erode riverbanks

Question 14

Ash eruptions (as a result of explosive eruptions)

Answer 14

• Smothers plants and prevents photosynthesis, which renders agricultural land useless in the short term.
• Deposits in thick layers on rooftops and places a heavy strain on buildings, causing them to collapse under the accumulative weight

Question 15

Poisonous gas emissions (as a result of effusive and explosive eruptions)

Answer 15

• The release of fine ash in explosive eruptions asphyxiates humans and animals
• Droplets of sulfur dioxide freeze in the stratosphere to form a fine mist of sulfuric acid aerosols that obscure the sun, decreasing global temperatures