Plate Tectonics

Continental Drift, Tectonic Plate Theory, Earth's Structure, Plate Boundaries, Landforms, Hot Spots (Magma Plumes)

Who is Ortelius and what theory did he propose?

In 1570, Ortelius published the first world atlas. He noticed that it looked as if South America and Africa could’ve once fit together. He said that Africa and South America got tore away from each other by floods and earthquakes.

What was the issue with Ortelius’ theory?

Ortelius had no real evidence to back up his theory

What is the theory of continental drift?

South America and Africa had drifted away from each other

Who proposed the theory of continental drift and in what year?

Alfred Wegener in 1912

Who was Alfred Wegener?

A German climatologist and geolist

What is the evidence for the theory of continental drift?

1. Geological column along coastlines of South America and Africa match

2. Matching mesosaurus fossil evidence along both coastlines

3. Matching ancient rock samples in the west coast of Africa and the east coast of South America (uranium, gold, diamonds, iron ore, oil/gas)

What was the issue with the theory of continental drift?

Wegener couldn’t explain how these massive continents could have moved. His theory could not satisfactorily answer the most fundamental questions raised by critics.

Explain how scientists are able to map what the planet may look like in the future

Sea floor spreading - a few cm of crust are produced each year by this process, so which effectively moves the landmass, so scientists can predict the movement.

EVIDENCE OF THEORY OF PLATE TECTONICS

What are the different layers of the earth called?

1. Lithosphere (crust and rigid upper mantle)

2. Asthenosphere (upper mantle)

3. Mesosphere

4. Outer core

5. Inner core

6. Inner inner core

Lithosphere

• Made of 2 layers, 50-100km thick

• a) crust (14°C)

• b) rigid upper mantle (1500°C at 100km deep)

Asthenosphere

• Upper mantle

• Hotter and semi-molten rock

• More fluid than the lithosphere

• Has a ‘plasticky quality’

• ~200km deep

• ~1700°C

Mesosphere

• Hotter still, but dense and more rigid

• Reaches down to the depth of 2900km

• ~3700°C

Outer core

• Liquid iron and nickel

• 200km thick

• 5000°C

Inner core

• Solid iron core

• 1200km thick

• 6000°C

• 6371km from surface

More theory of plate tectonics!

What are plate tectonics?

The process by which heated rock is moved within the earth in vast convection currents, which drag along the underside of the earth’s plates, forcing them to slowly drift across the planet

Define tectonic plate

A huge rigid slab of the earth’s crust

How many tectonic plates are there?

14

Continental crust:

• Thickness

• Age

• Density

• Composition

• 30-70km

• Over 1500 million years

• 2.6g/cm³

• Mainly granite

Oceanic crust:

• Thickness

• Age

• Density

• Composition

• 6-10km

• Less than 200 million years

• 3.0g/cm³

• Mainly basalt

What are faults and why are they dangerous?

Cracks in the Earth’s crust close to plate boundaries. They are dangerous because its along these faults that the most powerful earthquakes happen.

What happens to solid land when plates collide?

Land gets buckled and folded upwards into mountains (called ‘fold mountains’, e.g. Himalayas)

What is Mt Everest doing each year?

Growing 5mm/year

How hot is the lava lake at Mount Nyiragongo?

800°C on the surface

How fast can the lava from Nyiragongo travel?

60mph

What benefits does the heat from inside the crust bring to the people of Iceland?

In Iceland, the Earth’s heat is close to the surface - geothermal energy, heat foods and pools, heat pavements and roads during the winter

Explain why the earth’s tectonic plates are moving

Convection currents spreads out the tectonic plates and drags against the undersides of the plates, causing them to slowly move apart

How old is our planet?

4.5 billion years

How long have modern humans been around?

200,000 years

Describe how our planet and its different layers were first created

Rocks in space continually collided, generating huge amounts of heat. The rocks delivered radioactive