thin, solid rock of the earth's surface. Covered by oceans and part forms the land. It is about 5-55 km thick.
Below the crust. About 3000 km thick. Consists very hot semi-molten rocks (1600C) The lava of volcanoes comes from and goes through cracks in the Crust
Inner and Outer Core
Interior parts of the Earth. Very hot temperatures (2000C) Made out of NIFE (nickel+iron rocks) Very dense. Total radius is about 3500 km from the Earth's center
helps the crust of Earth float because the crust is less dense than the mantle.
The crust moves around because
The continental plate
less dense then the oceanic place
Why does the crust move?
Convection currents exist in the mantle. Heat flows from hotspots to cooler areas. The source of the heat driving the convection current is radioactive decay which is happening deep in the Earth.
What are the plates
crust breaks up into large segments
less dense rock (thickest crust up to 80km)
denser rock (thinner crust 10-12km)
Types of plate boundaries
When continental crust collides with oceanic crust
When two continental plates collide.
causes plates to get stuck
large super continent that scientists believe existed on Earth around 400 million years ago.
What is some evidence that the continents were once joined?
The shape of the continents fit together like a jigsaw
Same rock types and identical plant and animal fossils of the same age have been found in rocks in Africa and South America
Distribution of animals proves that places have separated.
Example : Africa - Cheetah, South America - Jaguar
Types of rocks found on each continent today show similar strata and ages. Mountain range on the coast of West Africa disappear then suddenly reappear again on the coast of South America.
How do we record earthquakes?
The strength or magnitude of an earthquake is measured by this. Measurements are logarithmic, this means that each whole number step represents a ten-fold increase in measure amplitude. This means a magnitude 7 earthquake is 10 times larger than a 6 and 100 times larger than a magnitude 5.
(Size of wave) enables us to record the amount of energy
recording device that measures earthquakes
Observational scale, assesing the damage cause from I to XII
Why are some earthquakes more damaging in some places than others?
Socio-Economic Factors - Population Density, Wealth of the area, Education of Population, Preparation
Physical Factors -Type of soil may mean liquefaction occurs, Proximity to coast, tsunami risk, Danger of landslide
Mitigation of Earthquakes
PREDICTION - What are some possible indicators of an earthquake?
Water levels in wells drop or rise
Build up of electro-magnetic radiation can be monitored
States that along faults that are seismically active, the regions that are more likely to experience earthquakes in the near future are those that have not shown seismic activity in some time.
PREPARATION - Civil Defense Organization
Civil Defense Organization
PREPARATION - Building regulation suggestions
Buildings need to be made of reinforced concrete.
A height limit should be placed on buildings in places that have sandy soils.
Land use zoning: Make it ilegal to build in areas that are unsafe.
PREPARATION - Education
Drills carried out by an institution
Simulations carried out by a whole area
PREPARATION - Rescue Teams
Ready for emergencies best provided in EMDCs
Name the times of periods that existed millions of years ago.
Permian-225 million years ago
Triassic - 200 million years ago
Jurassic - 135 million years ago
Cretaceous - 65 million years ago
Occur along plate margins (where plates meet). Happens when plates move past, towards or away from each other the movement is not smooth. Occurs when the build up of pressure (plates that get stuck and the pressure builds up) is released.
The point where the earthquake starts
The point at ground level directly above the focus
How does a seismometer work
The whole seismometer moves as the earth is attached to shakes but the heavy mass does not move because of its inertia. The recording device measures how far the rest of the seismometer has moved with respect to the mass.
How is the Mercalli Scale measured?
What are the two types effects of an earthquake?
Direct - effects that are caused by the earthquake
Indirect - Events set of as a consequence of the earthquake (there is a time delay)
What are Direct Effects of an earthquake?
downwards motion of earth's surface
when ground behaves like liquid and so loses its ability to carry weight