Geography Revision Yearest Of 9S

Front 1

Hazard risk

Back 1

Chance or probability of being affected by a natural hazard

Front 2

Evidence of plate tectonics - Fossils

Back 2

Fossils of certain prehistoric animals such as a Cynognothus have been found on separate continents (such as South America and Africa) yet the animal did not have any flight or aquatic features.

Front 3

Evidence for plate tectonics - Rock patterns

Back 3

Same rock, rock patterns and rock layers have been found in places like Greenland, UK and Africa west coast. This is because they were all part of the same mountain range, split by constructive plate boundary.

Front 4

Evidence of plate tectonics - Continental drift

Back 4

Continents such as North and South America look as if they would fit around Africa but been moved away by plate margins.

Front 5

Evidence of plate tectonics - Palaeomagnetism

Back 5

Minerals like iron line line up to face north because of the magnetic field. The magnetic field switches (north becomes south and South becomes north) every 100 000 years and the iron turns to face the new direction. This proves new sea floor spreading.

Front 6

Slab pull ridge push percentage against convection currents

Back 6

SPRP - 90% of plate movement

Convection currents - 10% of plate movement.

Front 7

Slab pull

Back 7

At a destructive plate margin, denser oceanic crust subducts into the earth's crust. When this happens, the crust is more denser than magma and it pulls the oceanic crust under.

Front 8

Ridge push

Back 8

When a lump is formed from rising magma between plates, the earth corrects itself by pulling the two plates apart. This is a constructive plate margin.

Front 9

Distribution of natural hazards - Earthquakes

Back 9

Earthquakes are normally found along conservative and destructive plate boundaries. An example is the California earthquake which is on the conservative plate boundary of the North American and Pacific plates.

Front 10

Distribution of natural hazards - Volcanos

Back 10

Volcanos are normally found along destructive and constructive plate boundaries. An example is the Iceland volcano, Katla, between the North American and Eurasian constructive plate boundary. An anomaly volcano is in Hawaii in the centre of the Pacific plate. This is because this area is a hotspot.

Front 11

Composite Cone lava

Back 11

Composite Cone Volcanos give high viscosity (sticky) lava. This lava does not flow far and hardens quickly.

Front 12

Shield lava

Back 12

Lava from a shield volcano is less dense and when it is erupted, the lava is runny and acidic. This lava is low viscosity.

Front 13

Shield volcanos

Back 13

Formed at constructive plate boundaries, shield volcanos are smaller with wide bases. They are made of lava only and there eruptions are effusive (gentle).

Front 14

Composite Cone Volcanos

Back 14

Formed at destructive plate boundaries, these volcanos are taller with steep sides. They are made of alternate layers of ash with violent, irregular eruptions.

Front 15

Earthquakes

Back 15

Earthquakes occur at destructive plate boundaries but mainly at conservative plate boundaries. They happen when pressure builds up when two plates are stuck and that pressure is suddenly released. That is called the Focus. The area directly above the focus is the epicentre. The closer the focus is to the epicentre, the more powerful the earthquake will be as the seismic waves given off from the epicentre do not have to travel as far.

Front 16

Waterfall formation and erosion

Back 16

Waterfalls have a soft rock layer in contact with water with a hard rock layer underneath. The soft rock is eventually eroded and the water is flowing on the hard rock. The sediment in the river erodes the rock below the hard rock and when there is no more support for the hard rock, it brakes and collapse into the gap below. This makes the river move upstream.