1A2 Geography27th January 2015

Objectives:To introduce students to the structure of the Earth’s interior, plate tectonics, and plate boundaries.

The Universe

• The word ‘Universe’ refers to space and its contents.

• The universe contains vast groups of stars called galaxies.

• The sun is one of billions of stars in our galaxy – the Milky Way.

The Solar System

• Earth is one of the eight/nine planets that orbit the sun.

• The sun and planets together make up the ‘Solar System.’

• The planets are heated and receive energy as they orbit the sun.

• Only Earth can support life.

Inside the Earth

• Imagine you could cut the world in half. What would you see?

• Four layers – the inner core, outer core, mantle, and crust.

Earth’s Inner Core

• This is located at the centre of the planet.

• It is a solid mass of iron and nickel.

• The temperature of the inner core is extremely high (6000°C – 7000°C).

Earth’s Outer Core

• This surrounds the inner core.

• The rock contained in the outer core is in a semi-molten state.

• Its temperature is also extremely high (4000° - 6000°C).

Earth’s Mantle

• This is located between the outer core and the crust.

• The mantle is Earth’s biggest layer.• It consists of molten (melted) rock called

magma.• The extremely high temperatures in the core

heat the molten rock in the mantle, causing convection currents.

Convection Currents

• Magma moves in a circular motion.• The intense heat of the Earth’s core warms the

magma in the mantle. As it is heated, it begins to move upward.

• As it is rising, it slowly begins to cool a little and eventually sinks.

• The process of heating and cooling causes the magma to move in circles (CONVECTION CURRENTS).

Convection Currents

Earth’s Crust

• This is the Earth’s outer layer.• The crust is thinner than the other layers.• It is not one whole piece – the crust is divided

into sections.• These individual pieces are called tectonic

plates.

Two types of plates

• Continental plates – these have land on top.

• Oceanic plates – these have water on top.

Earth’s Crust

• These plates rest on top of the magma in the mantle.

• The convection currents here can cause the plates to move in a process known as continental drift.

• Plates can be pulled apart, or collide with one another, as a result.

Plates Collide

• Destructive boundaries.• Leads to the formation of fold mountains and

volcanic mountains.• Causes earthquakes.

Plates Separate

• Constructive boundaries.• Magma comes to the surface where it cools

and solidifies to form volcanic mountains, volcanic islands, and mid-ocean ridges (e.g. The Mid-Atlantic Ridge, an under-water mountain range).

Plates move past one another

• Passive boundaries.• Can result in earthquakes and the creation of

fault lines (e.g. San Andreas Fault).