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Tectonic Terror Coping with earthquakes, volcanoes and tsunamis.

Natural Hazards - Tectonic Hazards Natural hazards are the risks we face due to nature. Drought, flooding and forest fires are examples of natural events which may pose a threat, or hazard, to people.

The land surfaces and the seafloors of the Earth rest on tectonic plates. It is the movement of the plates that causes earthquakes, volcanic eruptions and tsunamis.

They are known as TECTONIC HAZARDS.

Find out more‌ Structure of the Earth Plate Names and Locations

Plate Tectonics

How Continents Move

Volcano and Earthquake Distribution

Structure of the Earth Even though the Earth looks and feels uniform and solid to us, this is actually not the case.

The Earth consists of four layers: 1.The crust is the thinnest layer of the Earth - it is between 5 and 50 km thick.

This is proportional to the thickness of the peel around an apple. This is the surface layer we live on and where all our rocks, minerals and metals are found.

2.The mantle is the layer below the crust and consists of a plastic or viscous layer of molten rock. This material is known as magma.

3.The outer core surrounds the inner core and is more solid than the mantle.

4.The inner core is solid, consisting of iron and nickel at a very high temperature.

Plate Tectonics The crust of the Earth does not form a solid, unbroken layer. It is made up of interlocking plates that grow, get smaller and move around the Earth's surface at a very slow rate - only a few centimetres each year. If we go back about 300 million years, we find that the continents and the oceans were not in the positions we know today.

In fact, the Earth had only one continent known as Pangaea and only one ocean known as Pantallassa.

180 million years ago, the first split of the land mass resulted in two separate continents Laurasia in the north and Gondwanaland in the south.

How Continents Move Constructive plate boundary Convection currents move within the mantle. The currents well up under the crust and "float" the plates away from each other. In the centre, welled up magma solidifies, forming solid volcanoes along the plane of weakness of the oceanic ridges.

This is known as sea-floor spreading.

Destructive plate boundary As two plates meet or collide, the edge of one plate slides beneath another.

As the plate is pushed into the mantle, the plate melts and becomes part of the mantle. This activity occurs along the edges of fold mountain belts such as the Andes and the Alps.

This process is known as subduction.

Conservative plate boundary These occur when two plates slide past each other horizontally. No crust is added or lost, eg the San Andreas Fault in California.

Plate Names and Locations

Volcano and Earthquake Zones

Volcanoes •

Volcano erupts in Hawaii (Video) Helicopter footage of lava eruptions and flows on the Hawaiian volcano, Kilauea.

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Iceland volcano spews lava (Video) A volcano at Eyjafjallajoekull in southern Iceland continues to erupt under an ice sheet.

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Thousands flee Congo eruption Fires rage as mile-wide river of lava engulfs village

Hospitals are having to use every available area to treat people injured or affected by the earthquake and tsunami.

Walking through a disaster zone a man and his son survey the damage in their home town

Earthquakes •

Earthquake Eyewitness Report Teacher, Julianna Bozsik, describes her experiences in the 1989 Loma Prieta earthquake.

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Earthquakes: why they happen Earth tremors are going on all the time as the planet's rocks boil and move beneath us, but only some quakes do any damage.

Find out why ...

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Distribution of earthquakes and volcanoes An animated lesson on tectonic plate movement, and how this leads to earthquakes and volcanoes

Tsunami •

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We Lost Everything In A Second (Video) Survivor testimony from Miyagi prefecture recounts the devastating effect of the Japanese tsunami Rescue in Kesennuma (Video) Following shocking amateur footage filmed in Kesennuma, Jonathan Watts find hope in the rescue of an elderly couple from their home in the city Japanese tsunami survivors return to wrecked city (Video) Camcorder footage shot by a resident of Ishinomaki, Miyagi prefecture, chronicles life as an evacuee following Japan's earthquake and tsunami on Friday 11 March

This is a house found drifting in the Pacific Ocean following the massive earthquake and tsunami which destroyed many coastal regions in northern Japan on Friday

By Rex

A girl is rescued from the flood waters in Kessennuma

Why People Live in Dangerous Places You might think that sensible people would avoid dangerous places, but often the opposite seems to be true. Why would they do that?

Today, about 500 million people live on or close to volcanoes. We even have major cities close to active volcanoes, so lets look at four good reasons to live near a dangerous volcano.

Minerals

Fertile Soil

Energy

Tourism

Geothermal Energy •

Geothermal energy means heat energy from the earth. It's unusual to use the heat directly, by building your house on top of a steam vent for example, because it's unpredictable, dangerous and messy.

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The heat from underground steam is used to drive turbines and produce electricity, or to heat water supplies that are then used to provide household heating and hot water. Where steam doesn't naturally occur it is possible to drill several deep holes into very hot rocks, pump cool water down one hole and extract steam from another hole close by.

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The steam isn't used directly because it contains too many dissolved minerals that could precipitate out and clog pipes, corrode metal components and possibly poison the water supply.

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Countries such as Iceland make extensive use of geothermal power, with approximately two thirds of Iceland's electricity coming from steam powered turbines. New Zealand and to a lesser extent, Japan, also make effective use of geothermal energy.

Thousands of people near the Fukushima nuclear power plant have had to be evacuated from their homes because of the threat of radiation poisoning. The reactor has suffered a series of explosions and fires following the earthquake

People look at evacuation lists in the town of Natori hoping to see the names of relatives who have been moved to safety

Fertile Soils •

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Volcanic rocks are rich in minerals, but when the rocks are fresh the minerals are not available to plants. The rocks need thousands of years to become weathered and broken down before they form rich soils.

When they do become soils though, they form some of the richest ones on the planet.

Places such as the African Rift Valley, Mt Elgon in Uganda, and the slopes of Vesuvius in Italy all have productive soils thanks to the breaking down of volcanic rocks and ash.

The Naples area, which includes Mount Vesuvius, has such rich soils thanks to two large eruptions 35,000 and 12000 years ago. Both eruptions produced very thick deposits of ash and broken rocks which have weathered to rich soils.

Today, the area is intensively cultivated and produces grapes, vegetables, orange and lemon trees, herbs, flowers and has become a major tomato growing region.

A coffee bush growing in volcanic soil - African Rift valley

Tourism •

Volcanoes attract millions of visitors every year. There are few sights that can beat seeing an erupting volcano blowing red hot ash and rock thousands of feet into the air.

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Iceland markets itself as a land of fire and ice, attracting tourists with a mix of volcanoes and glaciers, often both in the same place. The wild, raw and barren volcanic landscapes attract tourists who want to see what the early planet may have looked like.

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Tourism creates jobs in shops, restaurants, hotels and tourist centres / national parks. Local economies can profit from volcanism throughout the year, whereas skiing, for example, has only a limited winter season.

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In Uganda, a country trying hard to increase its tourist industry, the volcanic region around Mt Elgon is being heavily promoted for it's volcanic landscapes, huge waterfalls and remote 'get away from it all' location.

Volcanic landscapes are marketed as a tourist attraction in Uganda, Africa

Minerals Magna rising from deep inside the earth contains a range of minerals. As the rock cools, the movement of superheated water and gasses through the rock deposit minerals at different locations. Thanks to volcanic activity, tin, silver, gold, copper and even diamonds can be found in volcanic rocks.

Most of the metallic minerals mined around the world, particularly copper, gold, silver, lead and zinc are associated with rocks found below extinct volcanoes. This makes the areas ideal for both large scale commercial mining and smaller scale local activities by individuals and small groups of locals.

Active and dormant volcanoes have the same mineralisation, so like extinct volcanoes, they are rich sources of minerals. Hot gasses escaping through vents also bring minerals to the surface, notably sulphur, which collects around the vents as it condenses and solidifies. Locals may collect the sulphur and sell it.

Why Hazards Become Disasters An earthquake or tsunami striking a place where nobody lives, farms or visits isn’t a disaster for humans. It is only when a natural hazard exists in an area where we live or work that hazards have the potential to become disasters.

Clearly, the best way to avoid tectonic disasters is to keep away from areas where they may occur, but we’ve already seen that there are often good reasons to live in the danger zones – generations may farm on fertile soils before the next eruption does any damage, and if you want to catch fish, you must live on the coastline.

So, what factors influence the size of a disaster?

A man on his bicycle – the only transport available.

Economic Development In developed countries, buildings are more likely to withstand earthquakes because they have the money and knowledge to create safer buildings, and adapt old buildings to withstand shocks.

Less fortunate countries lack both the money and the skills, and the results speak for themselves. In Kobe, Japan, a quake killed 5,000, yet a smaller quake in less developed Turkey killed 17,000.

Why Hazards Become Disasters Urban or Rural Location Urban areas have greater population densities than rural areas. If identical quakes were to hit rural and urban areas with the same safety precautions, the city, containing more people and buildings would be the worst affected location.

Distance From The Disaster Earthquakes are most powerful at the epicentre – the place on the surface directly above the source. As distance from the epicentre increases, the power of the shock waves decreases.

Tsunamis are most powerful along the coast.

As they move inland they lose energy and eventually run out of momentum.

Volcanoes discharge lava, ash and gasses. Lava and gas clouds stay fairly close to the volcano, being ejected into the air or flowing from the vent. Ash clouds can travel around the globe, but again, damage quickly reduces as distance from the volcano increases.

This devastated place used to be the village of Aragama - now people are left to sort through the debris of what used to be their homes, schools and offices

Why Hazards Become Disasters Weather and Seasons When disasters leave people injured, homeless or trapped they are vulnerable to the weather. More people will die in very hot, cold, dry or wet weather than in more pleasant and ‘average’ conditions.

Extreme weather also hampers rescue efforts. In areas where heating is provided by open fires and stoves, a disaster in winter carries a greater risk of house fires than a disaster in summer.

We’re living on the streets at the moment – so we need shelter too.

ActionAid

Why Hazards Become Disasters Time and Day of The Week The time and day at which a disaster strikes has an influence on human consequences.

Modern cities are packed with workers during the day, but many go home in the evening.

Schools are occupied during the day, but empty at night.

Office blocks are occupied during the working week, but probably empty on Saturday and Sunday.

Some children in Japan's capital city Tokyo have Cookers are on at meal times. If a disaster strikes when everyone is cooking, the risk of fires is greatly increased.

Sleeping people are not aware of what is happening around them; they may not hear of feel the warnings that come before a disaster.

taken to wearing a "disaster hood" which is designed to protect the head from falling bricks and debris if another earthquake was to strike

Quotes from victims of Japan’s earthquake and tsunami “My home is burning. I can’t go back there. It’s too dangerous. I’m staying with a friend but it’s though. We have no electricity, gas or water.

We can’t bathe. There are huge queues outside the shops and nothing to buy inside. We have no idea when our lifelines will return. It’s terrible, terrible.”

Emiko Mimura, Japanese evacuee, island of Oshima, Japan

“I’m hungry but what I most want is furniture, like a bed and a TV.” Yuto Hariyu, 15, Miyagi prefecture, Japan

“It’s terrifying. We have been hit by disasters and now we are being threatened by something we can’t even see. Any one of these dangers would be bad, but to be hit by three in a row is beyond imagination” Masakai Ohata, Kenssennuma City, Japan after the explosions at Fukushima nuclear power plant, following the earthquake and tsunami

Even airplanes have been found amongst the debris from the devastating tsunami - the force of the water just swept away everything in its way!

Rex

An aerial view of Minamisanriku - one of the devastated coastal areas of northern Japan.

The prime minister of Japan has said the country faces its biggest crisis since the

A woman and her dog walk among the debris.