The Earth’s surface

The crust

Earth's outermost layer.

The mantle

The layer of hot, solid material between Earth's crust and core. It is made up of molten rock called magma.

The core

Center of the earth. It is made up of iron and nickel. It is 6000 degrees Celsius hot.

Tectonic plates

Sections of the Earth's crust that move due to convection currents.
Plateswith land on top are called continental plates and plates that have oceans on top are called oceanic plates.

plate boundaries

The line where to plates meet is called a plate boundary.

Convection currents

When magma is heated in the mantle, it rises towards the crust.
•As it rises it cools and moves sideways. This causes friction between the magma and the crust and pulls the plates.
•The magma cools and sinks back down into the mantle.
•This process is constantly repeated.

Plate tectonics

The study of plates and their movements is called plate tectonics.

Pangea

Alfred Wegener looked at the shapes of the continents he thought they looked like pieces of a jigsaw puzzle, and his theory was that they were once all joined together. He called this huge land mass Pangaea, meaning 'all land'.

Continental drift

Pangaea then broke up and the continents moved to the positions they are in today. Wegener called this continental drift.

Sea floor spreading

The rocks formed by magma cooling along the ridge are younger than the rocks closer to the edges of the continents. This is called sea-floor spreading.

Constructive plate boundaries

•Plates that separate from each other are known as constructive boundaries. Here, new crust is created.
•Plates move apart from each other and a gap is formed between the two plates. Magma rises out of the mantle to fill the gap. The magma then cools and hardens to form new crust.
•Plates that separate form volcanic mountains, volcanic islands and mid-ocean ridges.

Destructive plate boundaries

Plates that collide with each other are known as destructive (or convergent) boundaries. Here, the crust is destroyed.
•Huge pressure is built up and the heavier plate is pushed under the lighter plate. This is called subduction. The heavier plate melts back into the mantle. The lighter plate is lifted up, forming fold mountains. Plates that collide also cause earthquakes and volcanoes.

Passive plate boundaries

Plates that slide past each other are known as passive boundaries. Crust is neither created nor destroyed.
•These plates are locked together and then release a huge amount of energy when they slide past each other. Sliding plates cause earthquakes and fault lines.

Mid ocean ridges

•Hot molten rock, known as magma, rises up from the mantle through the cracks in the crust. The magma then cools, hardens and builds up, forming new land in a ridge-like shape.
•Example: In the middle of the Atlantic Ocean, the American plates are separating from the Eurasian and African plates and the magma that rises up through the cracks or fissures there is creating a chain of mountains on the sea floor known as the Mid-Atlantic Ridge.

Volcanic islands

•Mountains on the sea floor formed when magma rises up through the cracks in the crust sometimes rise above the surface of the ocean. These mountains are called volcanic islands.
•Example: Iceland.

Volcanoes

•Magma can also rise up from a magma chamber in the mantle through a vent. A vent is a narrow tube in the Earth's crust. When the magma reaches the surface, we call it lava.
•Lava, hot ash and rocks are thrown into the air as the volcano erupts and an ash cloud is formed. There is a build-up of material around the vent.
•As more eruptions occur, layer is added to layer until a cone-shaped mountain is formed. The lava continues to flow from a crater at the top of the volcano

Types of volcanos

active, dormant, extinct

Positive socio-economic effects of volcanoes

•The soils made from lava are rich in minerals and so are very suitable for agriculture.
•Tourists visit the sites of some famous volcanoes, such as Mount Etna in Sicily, Italy.
•Water heated underground by volcanic activity can be used to generate geothermal energy to heat people's houses.

Negative socio-economic effects of volcanoes

•Gases produced by volcanoes, such as sulphur dioxide, can poison people who live nearby and cause acid rain. This can affect economic activities such as agriculture, fishing and forestry.
•A lava flow burns everything in its path. There can be huge loss of human life when a volcano erupts.
•When volcanic material mixes with water from rivers or rain or melting snow and ice, a river of mud called a lahar can be created. Lahars can destroy towns and villages in their path.

Earthquakes

•Earthquakes are sudden tremors or vibrations in the Earth's crust.
•When plates are pressing against (colliding with) or sliding past each other, there can be a build-up of pressure along the fault line. When the plates move, the sudden release of pressure results in an earthquake

Focus

The point beneath the surface where the earthquake happens is called the focus.

Epicenter

Point on Earth's surface directly above an earthquake's focus

Aftershocks

Smaller earthquakes that follow a major earthquake.

Measuring Earthquakes

A seismograph records the seismic waves released by an earthquake using a siesmograph.

Damage caused by Earthquakes

•There is loss of life.
•Buildings are damaged or collapse.
•Damage to electricity and gas lines may cause fires.
•Damage to sewers and water supplies may cause the spread of disease.
When an earthquake occurs under the sea, water can be displaced, making a huge wave called a tsunami.

Fold mountains

•Fold mountains form when two plates collide with each other. Here is how it happens:
•When a heavier plate and a lighter plate are pushed together and collide, the heavier plate sinks underneath the lighter plate and into the mantle.
•The lighter plate then buckles upwards because it has nowhere else to go, causing fold mountains to form.
Ex: The Andes Mountains

Alpine mountains

•The highest mountains in the world were formed about 30 to 35 million years ago during the Alpine folding period.
•Examples: The Alps in Europe, the Andes in South America, the Rockies in North America and the Himalayas in Asia.

Armorican Mountains

•This period of folding occurred when the Eurasian and African plates collided about 250 million years ago.
•Examples: MacGillycuddy's Reeks, the Galtees, the Comeraghs and the Knockmealdowns in Ireland and the mountains of the Black Forest in Germany.

Caledonian Mountains

•This period of folding occurred about 400 million years ago when the Eurasian Plate and the American Plate collided.
•Examples: The Dublin and Wicklow mountains in Ireland, the Appalachian mountains in North America and the mountains of Norway, Sweden and Scotland.

Tourism in mountainous areas

•People are attracted to the beautiful scenery in mountainous areas and the opportunity to take part in a variety of activities, including mountaineering, hillwalking, skiing, river rafting and rock climbing.
•Tourism provides employment for local people. There are many jobs for people who work directly with tourists, such as tour guides, bus drivers and waiters. Tourism also provides jobs indirectly - to people who supply food to the restaurants, for example.
•Tourism in mountainous areas can also have a negative impact on the environment and the local people. Buses and traffic cause pollution. Litter can also be an issue. Avalanches can occur on ski slopes because skiers dislodge the snow.

Farming in mountainous areas

•While farming is challenging in mountainous areas, it is still an important economic activity for the people who live there.
•The main type of farming in mountainous areas is cattle and sheep rearing.
•Crops are not usually grown in mountainous areas because it is difficult to use machinery on the slopes and the weather conditions are not favourable.
•In some mountainous areas, such as the Alps, cattle are brought up to summer pastures when the snow melts and fruit and vines are planted where terraces have been cut into the steep slopes.

Foresters in mountainous areas

•The physical landscape in mountainous areas means that forestry is sometimes the only suitable economic activity. However, when the trees are cut down it can lead to soil erosion, landslides and flooding.