Tectonic Hazards Flashcards
]Structure of the Earth
Out going in
Oceanic Crust
Continental Crust
Mantle
Outer Core
Inner core
Features of Inner Core
1,200 km thick
6,000+ Celsius
Made of solid Iron
Features of Outer Core
2,250 km thick
2,700+ Celsius
Liquid
Features of Mantle
2,900 km thick
3,000 Celsius
Viscous, softened rock & plastic
Features of Continental Crust
40-60 km thick
Very dense
Solid Granite
Features of Oceanic Crust
3-5 km thick
Least dense
Solid Basalt
Convection Currents
1) Rising convection current bring hotter less dense magma to surface
2) Magma is ejected & solidifies to form the new crust - plates diverge
3) Convection currents spread sideways carrying the plates with it
4) Magma descends back to the mantle to be reheated
Constructive Plate Boundary
1) Core heats up magma
2) Hot magma rises and solidifies to form new rock
3) Magma fills the gap
4) The crust gest pushed apart through Ridge Push
Example of a constructive plate boundary
South American & African Plate
Destructive Plate Boundary
- Convergent
- Subductive
1) Oceanic Plate gets pushed towards the continental plate
2) Less dense curst (oceanic) gets pushed under = subduction also known as slab pull
3) Crust starts to met due to pressure and heat in mantle
4) Pressure builds
5) Magma gets pushed up and volcano on land erupts
Destructive Plate Boundary
- Convergent
- Collision boundary
1) Two continental crusts push towards each other
2) Neither plate subducts so pressure builds up
3) Plates push upwards forming fold mountains under great pressure
4) The fold mountains will continue to grow due to continuous continental movement
Example of a Destructive Collision boundary
Himalayas
Conservative Plate Boundary
- Transform
1) Plates slide past each other - either same or opposite direction
2) No land is destroyed or created therefore no volcanic activity
3) There are many earthquakes as plates stick together and can cause friction
Example of a Conservative Transform Boundary
San Andreas Fault
How are Volcanoes formed
Rock is melted in a subduction zone, constructive boundary or hot spots.
The less dense magma rises and may flow onto the surface.
Gas and bubbles in the magma creates a higher pressure forcing the magma out of the volcano causing and eruption.
What scale can you measure volcanoes with?
What scales is it?
Volcanic Explosivity Index - VEI
0-8
Logarithmic (1,10,100 etc.)
What are Earthquakes?
A release of tension causing violent shaking of the ground from seismic waves.
Magnitude of earthquakes decrease further away from the epicentre
Earthquakes can be found at all plate boundaries as the earths crust is under the most stress on weak faults
Where is the epicentre
The point directly above the origin
Where is the origin/focus
Where in the earths crust the tension was released
Primary Hazards of Earthquakes
Ground Shaking
Aftershocks (can be argued secondary)
Secondary Hazards of Earthquakes
Fires
Floods (dam bursts)
Landslides
Disease outbreaks
Tsunamis
Liquefaction (unconsolidated rocks act like quick sand)
Primary Hazards of Volcanoes
- Lava Flow
- Pyroclastic Flow (Gas and volcanic material traveling down volcano at 700Celsius and 500mph)
- Gas Clouds
- Ash
- Volcanic Bombs
- Steam
- Volcanic Dust
Secondary Hazards of Volcanoes
- Forrest Fires
- Floods
- Lahars (Destructive mud flow made of volcanic debris and lava)
Hot Spot Formation
They form because there is a gap in the earths crust where lava can bubble up. Forming small islands such as Hawaii
Levels of Volcano Activities
Extinct
Active
Dormant
What does an Extinct Volcano mean
A volcano that will not erupt again
What does a Dormant Volcano mean
A Volcano that has not erupted recently but could do again
What does an Active Volcano mean
A volcano that has a recent history of eruptions and will do so again
2 main shapes of Volcanoes
Shield
Composite
Describe a Shield Volcano
Large Diameter & gentle sides
Lava, steam, volcanic bombs
1,000-1,200 Celsius Lava
Basic lava = runny, travels further
Erupts relatively frequently (every few years)
VEI = 0-1
Example of a Shield Volcano
Mauna Loa Hawaii
At what plate boundary are Shield Volcanoes found?
Constructive and Hot Spots
Describe a Composite Volcano
- Steep sided, Cone shaped, small diameter
- Lava, Ash, volcanic bombs, large quantities of Gas suddenly
- 650 - 1,000 Celsius Lava
- Acidic Lava - sticky doesn’t travel far
- Infrequent eruptions (200-300 + years)
- VEI = 5-6
Example of Composite Volcanoes
Mount Pinatubo, Philippines
Where are Composite Volcanoes found?
Destructive - Subduction Zones
