Unit 1: Global Hazard Patterns Flashcards
How are geophysical hazards distributed?
- Near plate boundaries
- plates move due to convection currents in the mantle.
- Volcanoes and earthquakes are the most common geophysical hazards to occur here.
Name the 4 types of plate boundaries
1) Destructive (Convergent)
2) Convergent (Collisional)
3) Divergent (Constructive)
4) Conservative (Transform)
Describe what happens at a convergent plate boudary
1) Destructive -> continental plate boundary and oceanic plate. Move towards each other. Oceanic crust is forced under the C plate as it is more dense. Crust melts and the pressure forces the magma through the crust. Volcano is formed and violent earthquakes occur. Mountains and oceanic trenches formed.
2) Collisional -> Two continental plates move towards each other. Continental cannot sink or be destroyed therefore both plates get pushed upwards. Fold mountains created. Violent Earthquakes occur.
Describe what happens at a Divergent/ Constructive plate boundary.
2 plates move apart. the gap between them allows magma to rise. This cools and creates new crust when it reaches the surface. E.G. mid-atlantic ridge
Gentle volcanoes and gentle earthquakes.
Describe what happens at a Conservative/ Transform plate boundary
2 Plates slide past each other. Get stuck on each other, pressure builds up between the two plates. Pressure is suddenly released and the sudden movement causes a violent earthquake. Crust isn’t created or lost. Fault lines are found at this boundary. Severe Earthquakes occur.
Describe the pattern of hydro-meteorological hazards
Drought, Floods, Storms
Drought- Spread out. 1/3 of lands surface ha exposure to drought.
Floods - Flooding is a frequent hazard and is evident in some 33% of the world’s area, which is inhabited by over 80% of its population. Regional-scale, high-magnitude floods are frequent events in India/Bangladesh and China.
Storms - tropical storms - occur over the sea when its above 26oC of at least 70m depth
What hazards is California prone to?
1) Earthquakes
2) Droughts
3) Tsunamis
4) Landslides
5) Volcanoes
Explain why California is prone to Earthquakes
- San Andreas fault
- COnservative plate boundary
- 2-3 EQs per year
- San Fran EQ 1906 - 7.8 mag - 700 deaths
Explain why California is prone to Droughts
- Caused by anticyclones. Dry sinking air means no rain
- Caused by La Nina - less evaporation, so less precipitation
- Increased wind blown from desert areas - dry air has mo moisture to cause precipitation
- Causes wildfires - fires spread quickly (Oct 2007 - killed 22 people and destroyed 1300 homes)
Explain why Cali is prone to Tsunamis
- caused by large waves that can flood coastal areas
- Mainly caused by EQs inder Pacific Ocean
- EQ off alaska caused tsunami to hit Cali in 1964. Killed 12 people
Explain why Cali is prone to Landslides
Can be triggered by EQs or coastal erosion or extreme rainstorms
- High in california because of building on and around steep slopes.
Why is California prone to Volcanoes?
On plate boundary
Last eruption was Lassen Peak in 1915
Volcanoes are all being monitored.
Why is California at high risk but at little vulnerability?
- Good infrastructure to cope with hazards
- Wealthy state so can afford to rebuild after a disaster
- Is able to educate population on what to do in the case of a disaster occurring.
- Has the correct equipment to help predict disasters
What hazards are the Philippines prone to?
Volcanoes Earthquakes Landslides Typhoons Tsunamis Droughts Flooding
What are the causes and impacts of Volcanoes in the Philippines
Near destructive plate boundary between the Eurasian and Philippine Plate. P plate is subducted under E plate.
- Mount Pinatubo - 1991 erupted - 847 killed in eruption. Disrupted agriculture of land. 2.1 million affected by it.
