Plate Tectonics, Earthquakes and Volcanoes!

This can be a particularly fascinating topic for pupils, nonetheless, it can be difficult to understand and grasp certain concepts. Therefore I will try and break it down into sizeable chunks, as well as making it enjoyable and interesting.

To understand earthquakes and volcanoes, it is vital to look at the Earth's plates. So what exactly are the Earth's plates and what do they do?

*The movement of the Earth's plates causes earthquakes and volcanoes.


*The map above shows the world's main tectonic plates. The point at which two plates meet is called a plate boundary.

*Most of the world's earthquakes and volcano zones are found on or near to plate boundaries.

The Earth's plates move in different directions, and there are three main types of plate boundary. These are listed below:
1) At a constructive plate boundary two plates move apart from each other.
2) At a destructive plate boundary two plates move towards each other.
3) At a conservative plate boundary two plates slide past eachother.

An easier way to remember this is that constructive plate boundaries create new land; destructive plate boundaries destroy land; and conservative plate boundaries neither create nor destroy land.

Plate Tectonics in more detail-

Constructive plate boundaries: At a constructive plate boundary (also known as a divergent plate boundary) two plates move apart from each other. As the plates move apart, magma rises through the gap in the Earth's crust and cools down to form new crust. An example is the Mid-Atlantic Ridge, where a chain of underwater volcanoes have formed along the plate boundary.

Destructive plate boundaries: At a destructive plate boundary (also known as a convergent plate boundary) two plates move towards each other. When an oceanic plate moves towards a continental plate, the denser oceanic plate sinks below the continental plate. As the oceanic plate sinks, it melts and forms magma. Magma sometimes rises through the cracks in the continental crust to form a volcano. In addition, at a destructive plate boundary, the movement of the plates may push the continental crust upward to form fold mountains. This process is called folding.

Conservative plate boundaries: At a conservative plate boundary (also known as a transform plate boundary) the plates move horizontally past each other, without creating or destroying the earth's crust. A famous example is the San Andreas Fault, USA.

Below is a diagram to show all three plate boundaries:

Earthquakes-

Instead of me blabbering on, here is a great video by the National Geographic on earthquake destruction:



We have established that the movement of the Earth's plates can cause earthquakes. So why is this? Plates do not move smoothly. Sometimes a plate gets stuck. Pressure builds up and when this pressure is released an earthquake can occur.

The point below the Earth's surface where the pressure is released is called the focus. The point on the Earth's surface directly above the focus is called the epicentre. When pressure is released from the focus, shock waves are produced. These waves are called seismic waves. The seismic waves are strongest at the epicentre of an earthquake. This is where the most damage is caused during an earthquake. The seismic waves spread out from the focus like ripples on a pond. As they travel outwards they lose energy.

Earthquakes can have a devastating effect on people and the environment. The immediate or primary effects of an earthquake include the collapse of buildings, roads and railways. People may be killed or injured and property is damaged. The long-term or secondary effects of an earthquake include gas explosions and fires. Communications can fail, as telephone lines and computer links are cut. Water can become contaminated as sewage and clean water pipes fracture. A lack of clean water can lead to the spread of disease. Below is a video of the Seattle earthquake of 2001. Have a look at the effects of the earthquake. Could it have been more devastating?



Nonetheless, the damage could have been worse if it wasn't for the fact that Seattle is in a MEDC. Natural disasters such as earthquakes tend to have as greater impact upon LEDCs than MEDCs. Buildings in LEDCs are not always strong enough to withstand the damage caused by earthquakes. LEDCs do not have sufficient healthcare facilities to deal with emergency situations. Access and communications in LEDCs tend to be poor. It is difficult to warn people about possible dangers on bring them emergency supplies. LEDCs also have limited money and resources to rebuild areas that are damaged.

Measuring earthquakes-

The strength of an earthquake is recorded using a machine called a seismometer. This picks up vibrations and tremors recording the strength of an earthquake. This strength, or scientifically known as magnitude, is measured using the Richter Scale.

Glaciation!

An Introduction-

During the Ice Age, many areas across the world were permanently covered by ice, including the UK. But what actually is glaciation?

A glacier is a body of ice that moves through a valley. Glaciers have shaped many landscapes through the processes of erosion, deposition and transportation. Glaciers are still shaping parts of the world today!

In more depth-

10,000 to 20,000 years ago, glaciers and ice sheets covered 32% of the land surface. Today 10% is covered by ice. 22% of the land is underlain by continuous or discontinuous zones of permanently frozen ground. The glacial age is not over, it has only diminished in its overall extent and intensity.

At maximum glaciation few areas of the earth were unaffected by ice activity and action. The last world-wide glaciation occurred during the Pleistocene epoch which comprised some twenty extreme cold periods interspersed by periods of milder weather, interglacials.


The Ice Age-

*During the last Ice Age, 2 million to 10,000 years ago the climate was much colder than it is today.
*In upland areas, snow remained on the ground all year. As more and more snow was added each year, it slowly compresses to form ice.

*In some areas, enormous ice sheets covered the whole landscape. The whole of northern Britain was covered in ice. Glaciers as a result have shaped many parts of Britain.
*In other places, ice only filled the valleys, forming glaciers. These glaciers moved downhill and shaped the landscape.
*Today, ice and snow still permanently cover countries within the Arctic Circle, such as Greenland, Northern Canada and parts of Russia.

In-depth Ice Age Britain-

No area of tge UK escaped the effects of the ice age: the landscape we see today was created by ice advances over the British land mass. Three main advances have been recognised:

*Anglican Advance (420,000-380,000 years ago, left major deposits in East Anglia)
*Woolstonian Advance (170,000-130,000 years ago, largely affected North Britain)
*Devensian Advance (115,000-18,000 years ago, depositional and meltwater features in Shropshire, Cheshire and Yorkshire)

Glaciation Erosion-

Glaciers form in hollows on the colder, sheltered side of a mountain. These hollows are called corries. Snow and ice gathers in the hollow and over time the corrie gets larger through freeze-thaw weathering. Freeze-thaw weathering also loosens pieces of rocks which then fall onto the glacier. This material is called moraine.

Inside the hollow ice begins to move in a circular motion, called rotational slip. Eventually the ice will move out of the corrie and over the lip of the hollow. The glacier movesa down the mountain-side. At the front of the glacier is the snout. A lake, called a tarn, may form in the corrie. The steep knife-edged ridge between the two corries is called an arete.


As a glacier moves it erodes in the landscape in two ways:

*Abrasion occurs when pieces of rock carried by the ice wear away the landscape. As the glacier moves it transports material with it, which helps the glacier erode and shape the landscape. The material can be frozen within the glacier or found underneath it.

*Plucking occurs when meltwater under a glacier freezes on to the rock surface. As the glacier moves forward it pulls away large fragments of rock from the surface.

Glacial Deposition-

As a glacier moves downhill, temperatures rise and the glacier begins to melt. As the glacier melts, it deposits the material it has been carrying. This deposition usually takes place in lowland areas. Glacial deposition can create distinct landscape features in lowland areas.

Moraine is the rock material carried by the glacier. It is later deposited to form mounds of unsorted rocks and rock particles, which are called moraines. There are several different types of moraine. These are classified according to when and where they were deposited by the glacier.

Types of moraine:


Other facts-

*Drumlins are mounds od boulder clay, deposited by glaciers and shaped by the moving ice. The ice moved over the drumlins to form small egg-shaped hills.
*Erratics are rocks transported many miles by a glacier and later found in an area of a different rock type.

Glacial landforms provide an important resource for the tourist industry. Glaciation helped to create distinctive and interesting landscapes like the Lake District. Tourists and day visitors may visit areas such as the Lake District to go walking, hiking, mountain climbing or absailing. Many glaciated landscapes are protected from large-scale urban or industrial development. Many are National Parks in rural areas where the main land use is for primary industry, such as farming or mining.

BBC Northern Ireland

There is a great site on the internet that focuses on five key areas of geography, relating it to areas within Northern Ireland. The five key areas are: Coasts; Mountains, Lakes and Rivers; Land Use and Economic Activity; Ecosystems and Settlement. The site covers geographic areas from Key Stage 3 to A Level. The link is provided below:

http://www.bbc.co.uk/northernireland/landscapes/teachers.shtml

River Landscapes and Processes

Key facts about the river system:

*The point where a river begins is called the source. Where the river reaches the end of its journey is called the mouth.

*The area of land drained by a river and its tributaries is called the drainage basin.

*Tributaries are the small rivers that join the main river channel. The point at which two rivers meet is called a confluence. The greater the number of tributaries, the denser the drainage basin.

*The boundary between two drainage basins is known as the watershed. A watershed is usually a ridge of highland.

Do you think you could draw a river system with the following features and label them? Try to plot these features into your diagram:

Watershed, source of the river, main river channel, tributaries, confluence, mouth of river.

Also, try these websites to further your knowledge on river systems:

GCSE: http://www.bbc.co.uk/schools/gcsebitesize/geography/riverswater/

A Level: http://www.s-cool.co.uk/alevel/geography/river-processes-and-management.html

Systems in Geography

Geography is often about systems. Examples can include industrial systems, ecological systems and farming systems. Geographical systems can be open or closed.

An open system has inputs and outputs.

A closed system has no inputs or outputs- it is a continuous cycle.

A river is an open system with inputs, processes and outputs. It is also part of a larger system called the hydrological cycle. This is explained in more detail in the post below: