Chap 1: The structure of the Earth and the theory of plate tectonics

Inner core

Iron, nickel, sulphur, 6000c

Outer core

Iron and nickel

Lithosphere

The rigid outer part of the earth, consisting of the crust and solid upper mantle

Asthenosphere

A layer of solid rock beneath the lithosphere where the extreme pressure and heat cause the rocks to flow like a liquid, semi-molten

Moho line

The boundary between the Earths crust and its mantle

Lower Mantle

Magma moves in convection currents. It rises and sinks here which causes endogenic forces

Continental crust

Crust with land on top, made of light rocks, e.g. granite. SIAL

Oceanic crust

Crust with oceans on top, made of heavy rocks e.g. basalt. SIMA

The theory of plate tectonics

This states that the Earths lithosphere is broken up into slabs of rocks known as plates. Plates would separate, collide, and move past each other.

Theory of continental drift

Alfred Wegner said the continents once formed a single landmass called Pangaea. He claimed it broke apart 200 million years ago, firstly into two supercontinents known as Laurasia and Gondwanaland.

Proof of Continental drift

1) Continental fit 2) Matching plant fossils 3) Matching animal fossils (Mesosaurus) 4) Matching rock folds (North America/North western Europe

The theory of convection currents

Arthur Holmes suggested convection currents move plates. Heated magma rises, cools, and sinks in circular-like motions, causing friction within lithosphere.

The theory of Seafloor Spreading

Hess (1960s) discovered that the oceans are creating new land. Two plates pulled apart, lava pours out, creates new sea floor. Oceans widened, e.g. Mid Atlantic Ridge, moves at 5cm annually.

The theory of subduction

Vine and Matthews discovered deep ocean trenches, realised that when two plates collide, one sinks into the mantle. Explains faster movements of some plates due to slab pull. E.g. Mariana trench