PLATE TECTONICS

THE POWER TO MOVE THE WORLD

PLATE TECTONICS

EVIDENCE OF CONTINENTAL DRIFT

• The continents fit together like a jigsaw puzzle. Not only is this apparent at the edges of continents, but where the continents end under the oceans it is even more apparent.

EVIDENCE OF CONTINENTAL DRIFT

• Glacial features and rock structures stretch across continents.

• A glaciated valley may end on one continent and continue on another, thousands of km away.

EVIDENCE OF CONTINENTAL DRIFT

• Fossils of the same creatures have been found on continents that are not only thousands of km apart, but which currently have vastly differing climates.

STILL NOT CONVINCED??

EVIDENCE OF CONTINENTAL DRIFT

• Continents are still shifting today, evidenced by the hundreds of earthquakes and seismic events that occur every year, particularly along plate boundaries.

PLATE TECTONICS

PLATE TECTONICS

PLATE TECTONICS

1. Hotspots are present in the Mantle

2. Magma rises towards the crust. Some magma (lava) erupts at the plate boundary.

3. The magma creates convection currents which move horizontally, dragging the plates apart.

PLATE BOUNDARIES

EARTHQUAKES

EARTHQUAKE EPICENTRES PLATE BOUNDARIES

EARTHQUAKES

EARTHQUAKE EPICENTRES PLATE BOUNDARIES

EARTHQUAKES

• The maps in the previous slide illustrate that earthquake activity is almost exclusively limited to the areas along plate boundaries.

• Some seismic activity may occur in other areas, like deep mining regions, but most earthquakes occur where movement of plate boundaries is most likely.

EARTHQUAKES

THE SAN ANDREAS FAULT SAN ANDREAS FAULT VISIBLE ON THE EARTH’S SURFACE

EARTHQUAKES

Origin of earthquakes Origin of earthquakes

• As the plates slowly grind past each other, tremendous pressure builds up.

• The pressure builds until the plates suddenly shoot forward, sometimes by many metres.

• This sudden movement of the plates creates shock waves or intense vibrations which ripple through the crust.

EARTHQUAKES

SEISMOGRAPH SEISMOGRAM

• The seismograph measures the faintest seismic movements and records this on a seismogram

EARTHQUAKES: Measuring the Magnitude

• The Richter Scale – A scale of 1 – 10

– Each level indicates a tenfold increase in severity

– 1-2 only felt by instruments

– 3-4 minimal damage

– 5-6 damage in the immediate vicinity

– 7-8 major damage

– 9 + Destruction over 100’s of km.

EARTHQUAKES: THE EFFECTS

PRIMARY EFFECTS SECONDARY EFFECTS

Effects which occur during or as a direct result of the earthquake: EG: Destruction of buildings Destruction of infrastructure Damage to transport networks Tsunami Injuries and fatalities

Effects which occur minutes, hours, days or even months after the earthquake, and which are not caused directly by the earthquake: EG: Flooding Fires and explosions Disease Economic breakdown Basic services cut off