Plate Tectonics

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Slide 1

Earth Materials – Geology Plate tectonics

Why have all the mountains not worn away by now?

Slide 2

Earth Structure

Radius 6300-6400km

Thin crust

Mantle extends almost halfway to the centre

The core makes up the rest

Slide 3

Composition

Low density solid crust floating on an almost solid mantle

But overall the Earth is dense

The core must be very dense

Probably made of dense metals nickel and iron

Hot liquid outer core and solid inner core

Slide 4

Rock Cycle

Weathering breaks down the rocks

Erosion wears them into smaller pieces as they are transported towards the sea

Slide 5

Deposition of sediments

Most sediments settle in water

Currents and waves form ripple marks

Evidence can be found for this in the rock

Ripple marks can be preserved in the rock

Slide 6

Sedimentary rocks

Grand Canyon

Youngest rocks at the top

Rocks and fossils older as you go down

Slide 7

Unstable Earth

The Earths crust is subjected to huge forces

Very large forces can fracture the rock

This can be seen as fault lines in the rock layers

Slide 8

Tilted and Folded

Sedimentary rocks are often found tilted

They can also be folded by the huge forces

This has happened at Lulworth cove

Sometimes the rock layers can even be turned upside down

Slide 9

Alfred Wegener

Some people thought the Earth was shrinking and cracking

Wegener thought whole sections of the crust moved (plate tectonics)

Some people did not understand and thought the continents floated around in the oceans (continental drift)

He died before people accepted his ideas

Slide 10

Tectonic plates

Slide 11

Evidence

Same fossils and rocks found in different parts of the world

Africa and South America look like pieces of a jigsaw

Slide 12

Earthquakes