Natural Hazard Risk – The probability or chance that a natural hazard may take place

Here is the hazard. What is the risk (hazard risk)? Well, just take a look at the probability or chance as if this were a horse race.

Natural hazards include earthquakes, volcanic eruptions, tsunamis, landslides, floods, droughts, hurricanes, tornadoes and asteroid impacts.

Apart from these geological and atmospheric hazards, there are also insect infestations, disease epidemics and wildfires.

While it cannot be eliminated, the risk to humans from natural hazards can be minimized. Taking action to minimize this risk is called hazard mitigation.

Risk and vulnerability can be reduced if there is a means of predicting a hazardous event. For instance, meteorologists may forecast sustained heavy rain and issue flood warnings so that those likely to be seriously affected can take action to protect possessions and leave their homes before the flood arrives. 

Seismologists may report greater risk of a volcanic eruption when their equipment registers increased seismic activity so that people living nearby can move away before the eruption begins. 

The experts carefully assess the risks of natural hazards they know are coming before issuing advice. But some – including many earthquakes – arrive without prior warning, leaving people unprepared.

Natural Hazards – A natural event, for example an earthquake, volcanic eruption, tropical storm or flood that threatens people or has the potential to cause damage, destruction and death

Nature always has hard ways (natural hazard) of bringing destruction and loss of life

All these events affect human lives

Tectonic plates

The surface of the Earth is split up into a number of large sections of rock called tectonic plates.

Try to recall the following picture to help you recall that these plates are called tectonic plates:

Subduction – When one tectonic plate is partly forced beneath the other as the two collide

The submarine ducked down under waves after the captain shouted, "Action (subduction) Stations!" She was forced beneath the ice cap.

Subduction occurs when a less dense tectonic plate collides with a denser one. The denser and heavier tectonic plate is forced underneath and is melted by the magma in the earth's mantle.

When two thin oceanic crusts converge (called destructive plate margin) the denser crust will subduct.

When destructive plate margins in the ocean occur, trenches form and so too do volcanic islands, all along the plate margin.

When a thin oceanic plate converges with a denser continental (land) plate  (again, called a destructive plate margin) the oceanic crust will subduct.

Again, subduction is when one crust is forced beneath the other as the two collide.

Plate Margin – The margin or boundary between two tectonic plates, the edges of the plate

The plate had margarine (plate margin) around the edges.

There are three types of plate margin – conservative, constructive and destructive. There is more information about these on the following three pages.

Constructive Plate Margin – Tectonic plate margin where two plates are moving apart

The construction (constructive) of a bridge was necessary when the two cliffs moved apart.

Plate margins are the boundaries or edges of tectonic plates.

With constructive plate margins, the two tectonic plates move apart or diverge from each other. This can occur both on land and in the ocean.

Convection currents of magma (liquid rock) in the earth's mantle (the layer below the earth's crust) move in opposite directions and force the two tectonic plates apart.

The gap this creates allows magma to escape and erupt onto the surface which can result in a volcano. The movement of the plates over the earth's mantle can cause earthquakes.

This does happen under the ocean too.

Destructive Plate Margin – Tectonic plate margin where two tectonic plates converge or come together

She destroyed (destructive) the edge of the plates by banging them together.

There are three types of destructive plate margin:

1. Where two thin oceanic crusts converge in the ocean.
2. Two thick continental (land) crusts converge on land.
3. A thick continental (land) crust and a thin oceanic crust converge where land and sea meet.

Note: There are no such thing as a purely continental (land) tectonic plate. Tectonic plates are mainly so big they vary around their edges or margins and across their surfaces from crusts in the ocean to thick crusts on land.

Conservative Plate Margin – Tectonic plate margin where two tectonic plates slide past each other

The two Conservative (conservative) members of Parliament slid past each other in the corridor.

Note: In the U.K. the main two political parties are Conservative and Labour.

Plate margins are the boundaries or edges of tectonic plates.

With conservative plate margins, two tectonic plates either slip past each other in opposite directions or at different rates in the same direction.

The tectonic plates do not move past each other smoothly. There will be a build up of friction until they suddenly move causing earthquakes.

Volcano – An opening (a hole) in the Earth's crust from which lava, ash and gases erupt

VOLCANO

The 'O's in volcano are there to remind you that volcanoes occur because of an 'O' (hole) in the Earth's crust.

There are two main types of volcano – composite volcanoes and shield volcanoes. There is more about these on the following two pages.

Composite Volcanoes – Volcanoes that happen on destructive plate margins

On the compost sit the Vulcans (composite volcanoes) but they quickly run away when there is a violent eruption that destroys plates (destructive plates).

Composite volcanoes occur on destructive plate margins, where the oceanic crust sinks beneath the continental crust (see subduction). Composite volcanoes have these characteristics:

• Acidic lava, which is very viscous (sticky)
• Steep sides, as the lava doesn't flow very far before it solidifies
• Alternate layers of ash and lava. For this reason they're also known as stratovolcanoes (strato means layers)
• Violent eruptions
• Longer periods between eruptions

Shield Volcanoes – Volcanoes that are found on constructive plate margins

The shield that the Vulcan (shield volcano) used was easy to construct – you just cut out a plate and paint the margins (constructive plate margins).

Shield volcanoes happen on constructive plate margins. This is where two plates move away from each other. A shield volcano has these characteristics:

• Basic lava, which is non-acidic and very runny (low viscosity)
• Gently sloping sides, because the lava flows for long distances before it solidifies
• No layers, because the volcano consists of lava only
• Less violent eruptions
• Usually shorter periods between eruptions

Shield Volcano.

Primary Effects – The initial (first) impact of a natural event on people and property

The boy's first day at primary school had an effect on his dad.

Primary effect = First effect

Ground and buildings having collapsed due to an earthquake are examples of the first effects or primary effects of a tectonic hazard.

The primary effects of a big earthquake include the ground shaking, ground splitting open (rupture), buildings collapsing and serious damage to roads, railways and bridges.

Secondary effect – Those effects that happen as a result of the initial effect (primary effect) but later on

As the seconds (secondary) ticked by while she stood on the beach after the earthquake, she thought she would be ok – but there was a large after-effect coming.

The main secondary effects of an earthquake are:

• Fires, often involving ruptured gas lines

• Tidal waves, which can cross entire oceans before engulfing land thousands of miles away.

• Landslides, which cause huge amounts of material to move very quickly

• Diseases, such as typhoid and cholera, which can spread in the unsanitary conditions often left behind by a major earthquake

Hazard Protection – Actions taken before a hazard strikes to reduce its impact, such as educating people or improving building design

Man has hard time over protection (hazard protection) idea: His wife said they needed to protect against the next earthquake so he built a jelly house. It wasn't quite what she meant...

Measures that can help to protect people from the ravages of an earthquake or other natural hazard include:

• Monitor tectonic and weather activity to be able to predict major events
• Set up evacuation zones and routes
• Educate people about what they should do to prevent injury, loss of life and property
• Make all new buildings as earthquake-proof as possible, and strengthen existing buildings
• Ensure well-trained teams are in place ready for emergencies
• Reduce inequality and poverty in countries to ensure everyone has the same status and right to protection

Biodiversity – The variety of life in the world or a particular habitat

The way to remember this term is to split up the word into two; bio and diversity.

Bio means life or living. To remember this, recall that:

The Biro (bio) pen suddenly came to life.

And diversity means variety or a range of different types.

So now we know this, it follows that:

Bio-diversity = Life-variety

Biodiversity means life variety; or the variety of life in the world or a specific habitat.

Biodiversity is short for biological diversity, which simply means the variety of life on Earth, or in a particular region.

A larger number of species boosts ecosystems – communities of interacting organisms in which each species has an important role to play.

Healthy biodiversity provides many advantages, including better soil formation, pollution breakdown and absorption, more abundant food, better climate stability and quicker recovery from unpredictable events.

The tropical rainforests have high biodiversity and this occurs because they have large amounts of rain and sunshine there.

Air at the equator rises and cools, condensation then occurs forming rain.

This is why tropical rainforests are found within 1000km (650 miles) either side of the equator.

Commercial Farming – Farming to sell produce for a profit to retailers or food processing companies

The TV commercial on farming (commercial farming) showed the farmer growing crops to make money.

Commercial farming usually means farming on a large scale, using few workers but plenty of machinery and technology. A commercial farm usually produces one crop, so it is a "monoculture". The crops, for instance coffee or flowers, are often called "cash crops".

There are arguments in favour of commercial farming – for instance, economy of scale and high productivity. However, many are against it. They claim it is leading to the destruction of rain forests; it pushes up the price of land because its use of vast acreages creates a shortage; growing the same crop on the same land season after season can lead to mineral depletion and plant diseases; and commercial farms tend to use chemicals that can harm people and the environment.

There's also the argument that commercial farming mostly does not help local or regional communities because the farms are owned by big business and the crops are mostly exported.

Debt reduction – Countries are relieved of some of their debt in return for protecting their rainforests

Your debt is reduced (debt reduction) if you stop reducing your trees (protect rainforests).

Between twenty and forty years ago, debt accumulated by some developing countries was leading to deforestation. Their leaders turned to the exploitation of natural resources as a means of affording interest payments to international banks.

Some organisations that are owed money by developing nations are now cutting the debts in return for the poorer countries providing protection of their rainforests.

While this debt relief has resulted in a slowdown of deforestation in some instances, private sector investment and even some state-owned banks are still driving commercial exploitation of rainforests. They invest in industries such as timber and mineral extraction that result in large areas of forest being cleared.

Deals that secure agreements to protect rainforests between nations that owe money and the lenders in better-off countries are often referred to as "debt-for-nature swaps".

Deforestation – The chopping down and removal of trees to clear an area of forest

The forest station (deforestation) took all the chopped down trees and cleared the logs away.

Deforestation is particularly problematic in tropical rainforests because these areas are extremely biodiverse (have a huge number of different species that depend on their habitat remaining stable).

Deforestation has many causes. Trees may be cut down for use in construction or to be burnt as solid fuel; or they may be cleared so that the land can be used as livestock pasture or for planting. Other causes include population growth (building of homes and facilities) and an increase in forest fires due to climate change.

The loss of large numbers of trees without sufficient reforestation (replanting) has resulted in habitat damage, biodiversity loss, and aridity (drying out of the land).

Ecotourism – Responsible travel to natural areas that conserves the environment, sustains the wellbeing of the local people and may involve education

He co-ordinated tourism (ecotourism) to preserve nature.

Ecotourism is a form of travel that involves visiting fragile, pristine and relatively undisturbed natural areas. It is an alternative to standard commercial mass tourism. Its desired outcomes include financial benefits for the conservation of the environment and improvement of the wellbeing of local people.

For the travellers, it delivers memorable experiences and helps raise sensitivity to the host country's environmental and social climates.

It is intended to be educational for the traveller and to foster respect for different cultures and human rights.

However, there is also a negative side to ecotourism. Critics claim it puts extra pressure on the local environment and leads to the development of additional buildings and amenities. This can result in deforestation or the development of other types of natural land.

Animals and plants may be disturbed. Travel to the countries being visited is usually by air, which puts more CO₂ into the atmosphere.

The point has also been made that most ecotourism firms are owned by investors outside the visited countries. This means that the majority of profits go to investors rather than being ploughed into the local economies or environmental protection schemes.

Logging – The business of cutting down trees and transporting the logs to sawmills

Logging is the process of cutting down trees and moving the logs from the forest to the sawmills.

One of the major causes of rainforest destruction is logging. Many varieties of wood are taken from tropical rainforests to make furniture, flooring, ornaments and other items. People in developed countries who buy certain wood products are contributing to the destruction of rainforests. Many rainforest animals cannot survive in the new, more open environment created by logging.

Another aspect of the problem is the reliance on wood from rainforests for firewood and building materials. In some areas with bigger human populations, the large number of people taking wood from a rainforest can have hugely damaging effects.