Natural Environment

Waterfall – Niagara Falls

The Niagara Falls are along the border between Canada and the United States and 51m high. Waterfalls are where water descends vertically. Waterfalls are usually created by a change in rock type. As the river moves from hard rock to soft rock, erosion increases at the soft rock, creating a waterfall.

As the water falls over the waterfall it erodes the river bed and the bottom of the waterfall. This makes a plunge pool and causes some undercutting. The undercutting creates an overhang which will eventually become too heavy to be supported and collapse into the plunge pool. The whole process then starts again, which means the waterfall is constantly retreating upstream towards the source. As the waterfall retreats it leaves behind a gorge.

Gorge: A gorge is a deep sided valley left behind when a waterfall retreats

Benefits from living near waterfalls Beauty Tourism (Niagara, Victoria, Angel, Iguazu) Jobs related to tourism e.g. guide, hotelier Possible HEP potential

Possible Problems of living near waterfalls Danger from fast flowing water (drowning) Problems of creating transport links across or near falls (gorge) Overcrowding an pollution from becoming a tourist location Navigation problems up and down river

Delta – Ganges Delta in Bangladesh

When a river meets the sea its velocity suddenly reduces. This reduction in velocity means that much of the rivers load is deposited at the mouth of the river. If the river deposits quicker than the sea can erode then a delta starts to develop. Usually in areas of a small tidal range. Deposition can mean that the main river channel gets blocked, forcing the water to find alternative routes to the sea by making distributaries. Deltas have very fertile soil and tend to be excellent for farming. There are three types of delta; arcuate, cuspate and bird's foot.

Distributary: A distributary is a small river or stream that breaks off from the main river in deltas.

ADVANTAGES OF LIVING IN GANGES DELTA

DISADVANTAGES OF LIVING IN GANGES DELTA

Fertile land for farming, especially crops like rice

Plenty of water for fishing or aquaculture. This can feed families or provide an economic income.

Abundant drinking water

Water for cooking, washing, etc.

Tourism opportunities

Houses can be built on water and are then transportable and they do not flood

Good transport links, possible to trade

Hard to make transport links by roads - cost of bridges

Areas are at constant risk of flood

Vulnerable to rising sea levels

Water is often dirty and polluted (industry, agriculture, sewers)

Mosquitoes are attracted to water (Malaria, Dengue)

Storm surges from tropical storms

Cost of building defences

Between 125 and 143 million people live on the delta,[citation needed] despite risks from floods caused by monsoons, heavy runoff from the melting snows of the Himalayas, and tropical cyclones. A large part of the nation of Bangladesh lies in the Ganges Delta, and many of the country's people depend on the delta for survival.[3]

It is believed that upwards of 300 million people are supported by the Ganges Delta, and approximately 400 million people live in the Ganges River Basin, making it the most populous river basin in the world. Most of the Ganges Delta has a population density of more than 200 people per km2 (520 people per square mile), making it one of the most densely populated regions in the world.

Approximately two-thirds of the Bangladesh people work in agriculture, and grow crops on the fertile floodplains of the delta. The major crops that are grown in the Ganges Delta are jute, tea, and rice. Fishing is also an important activity in the delta region, with fish being a major source of food for many of the people in the area.

In recent years, scientists have been helping the poor people of the delta to improve fish farming methods. By turning unused ponds into viable fish farms, and improving methods of raising fish in existing ponds, many people can now earn a living raising and selling fish.

Cyclones and flooding

In November 1970, the deadliest tropical cyclone of the twentieth century hit the Ganges Delta region. The 1970 Bhola cyclone killed 500,000 people (official death toll), with another 100,000 missing. The Guinness Book of World Records estimated the total loss of human life from the Bhola cyclone at 1,000,000.

Another cyclone hit the delta in 1991, killing about 139,000 people.

People have to be careful on the river delta as severe flooding also occurs. In 1998, the Ganges flooded the delta, killing about 1,000 people and leaving more than 30 million people homeless. The Bangladesh government asked for $900 million to help feed the people of the region, as the entire rice crop was lost.

Coral Reefs – Great Barrier Reef Australia

A coral reef is a line of coral polyp found in warm shallow seas. Polyp are tiny carnivorous (meat eating) animals. Polyps live in groups called colonies. A polyp has a mouth at one end. The mouth is surrounded by a number of tentacles. These tentacles resemble feet, which is how they get their name ('polyp' is a Greek word meaning 'many feet'). Polyps cannot move from their limestone homes. They mostly feed at night.

A polyp reproduces by dividing its own body to form two polyps, or by producing sperm and eggs. Each polyp builds a case of limestone around itself, using calcium from the water. It is like a house, with a floor and walls. This remains after it has died and forms a foundation for another polyp to build a house on, putting a floor on the roof of the old one. When these limestone formations increase, they are called a coral reefs.

Coral reefs are very delicate and need the following conditions to form:

Tropical sea conditions (between the two tropics) Warm waters (ideal 25 degrees but must be over 18 degrees centigrade year

round) Clear water ( no sediment) No pollution Sunlight Water less than 60 metres deep

Coral Reef Protection

Damaging fishing practices like dynamiting can be banned. It is important that this is enforced or the practices will carry on.

Conservation zones where tourists aren’t allowed or there numbers are restricted can be created.

Areas where coral reef cannot be farmed can be created Fish stocks can be enhanced and quotas imposed on amount being caught Sewage outlets can be moved downstream of coral reefs Banning the dropping of anchors on coral reef. Reduce the use of fertilisers near coral reefs Finally one of the most important is educating people about why coral reefs

are important and how we can protect them.

BENEFITS OF CORAL REEFS HOW CORAL REEFS ARE BEING DAMAGED

They support 25% of marine species (about 1 million species of plants and animals)

They protect coastlines from erosion

They form as a natural barrier against tropical storms and even tsunamis (they can absorb energy).

Act as natural recycling agent for carbon dioxide from sea and atmosphere

They contribute material to the formation of beaches (eroded coral reef)

They are source of raw material (coral for jewelery and ornaments)

Many species are being found to contain compounds useful in medicine.

They benefit the tourism industry because many people like to dive and snorkel over coral reefs

They provide important fishing grounds

The global value of coral reefs in terms of coastal protection, fishing and tourism has been estimated at $375 billion.

Rising sea levels mean that the depth of water above coral reefs is increasing. This means that in the future many coral reefs will not receive enough sunlight to survive.

Increases in the global climate means that many corals are being bleached. Coral reefs are extremely sensitive to changes in temperature and can bleach (die and turn white) even with only small increases.

Hurricanes. Although coral reefs act as a natural defence against tropical storms, they can be severely damaged during tropical storms.

Fishing techniques like dynamite, cyanide and trawling can damage corals. Corals are sensitive and take hundreds and thousands of years to grow.Damaging fishing techniques therefore can cause long term damage.

Deforestation. As areas of land are deforested, especially in the tropics (Indonesia, Thailand, Philippines) there is greater surface run-off and more sediment enters the rivers and is ultimately discharged into the sea. The increased sediment reduces visibility and means less sunlight reaches the coral.

Overfishing. Not only do damaging fishing techniques damage the coral but also overfishing. Coral reefs have very delicate food webs and if you remove elements of the food web, it can upset the balance of the reefs.

Pollution. The growth of urban settlements and tourist developments, as well as increased coastal traffic can also cause pollution to reefs.

Tourism. Tourism can damage reefs in many ways. Anchors from tourist boats can damage reefs. Motor boat engines can kill animals. Divers can touch and damage coral and tourist developments can release pollution.

Marine trade. There are many products, like coral, turtle shells, star fish and sea shells that get removed from corals and sold. This removal of coral and animals damage the reefs.

Tropical Rainforest – Amazon Rainforest, BrazilDistribution Tropical rainforests are found on or near the Equator (roughly between 28 degrees north and south). The main concentrations of tropical rainforests are:

The Congo Basin in central and west Africa

The Amazon in Brazil, Peru, Bolivia and Ecuador

SE Asia (Malaysia, Thailand, Vietnam, Indonesia and the Philippines)

Madagascar

North east Australia

Southern India and Sri Lanka

Central America

Deforestation rates vary massively, one reason is the inaccessibility of many of the forests and the way people classify deforestation. However, it is claimed that now only about 5% of the earth's surface is covered in tropical rainforests, compared to nearly 15% 50 years ago. Many people believe that tropical rainforests could disappear this century.

Tropical Rainforest Climate

Because tropical rainforests are close to the equator, they have very similar climates all year around. Their temperature is constant at between 25 and 30 degrees Celsius. They also receive rainfall all year around, although the monthly amounts may vary slightly. Tropical rainforests normally experience convectional rainfall. This is because they are close to the equator where temperatures are hot. The hot temperatures warm up the land, causing evaporation and transpiration and then convection. Not only is the weather similar between months, it is also very similar between days. Days will start of warm and then the temperature and humidity will build up. By the afternoon the air is saturated and tropical rainforest normally experience intense rainstorms. Because tropical rainforests are near to the equator the hot air rises causing low pressure.

Importance of Tropical Rainforests

Reasons for Deforestation Problems Caused by Deforestation

Biodiversity: Although rainforests cover only about 5/6% of the world's land mass, it is estimated that they could contain up to 50% of the world's biodiversity. This is potentially up to 15 million species.

Photosynthesis: Tropical rainforests are often referred to as the 'lungs of the earth' and convert large amounts of the greenhouse gas carbon dioxide back into oxygen. It is estimated that the Amazon rainforest alone produces about 20% of the earth's oxygen.

Flood control (interception, transpiration): Rainforests are an excellent natural measure to reducing flooding. There is leaf cover in rainforests all year so interception continually happens, extending rivers lag time. All vegetation uptakes water and transpires it.

Control of soil erosion: The root systems of trees and shrubs hold the very thin soil of rainforest in place. If trees are removed then both erosion of topsoil and landslides are more likely

Source of nutrients to humus layer in soil: The topsoil in rainforests is very thin and relies on the nutrients provided by rotting plants and animals. Because of the rainforests climate, there is a constant supply of leaf litter.

Medical remedies: Rainforests have been the source of many of today's

Cattle Ranching: As the world's population gets bigger and richer, the demand for meat is increasing. To rear the cattle increasing tracts of the rainforest are being cleared to make pastures for grazing.

Subsistence Farming: Because of the large amounts of poor people that still live in tropical areas, subsistence farming is still widespread. Because rainforest soil loses its fertility quickly after deforestation, the most common form of subsistence farming is slash and burn. With growing populations this method of farming can cause widespread deforestation.

HEP: Many of the world's great rivers flow through rainforests e.g. the Amazon. These great rivers often have the most HEP potential. Unfortunately when a dam and reservoir are built it causes damage during construction, but also floods large areas.

Mining: With an ever increasing demand for the world's natural resources, countries and companies are looking at increasingly isolated locations, places like rainforests and Antarctica. The rainforests are believed to have many resources including metals and fossil fuels beneath their soils. Gold mining can be particular damaging as mercury is used in its extraction and often runs off into rivers.

Road building: Building new roads like Trans Amazon highway from Brazil to Bolivia not only causes deforestation itself, but its also opens up new areas to urbanisation, mining and farming causing further deforestation.

Flooding: Flash floods become more common after deforestation because there is less interception and less root uptake and transpiration. As such rainwater reaches the ground quick, saturating it and causing surface run-off and potential flooding.

Landslides: By removing trees and vegetation, you are making the soil less stable. Combine this with saturated ground and the likelihood of floods increases.

Biodiversity loss: Because all the species that live in the rainforest are not known it is hard to calculate species loss. However, scientists believe that 1 mammal or bird extinction can be extrapolated to approximately 23,000 extinctions.

Reduced photosynthesis: As more and more trees are removed the rate of photosynthesis reduces, releasing more carbon dioxide into the atmosphere and contributing to the greenhouse effect.

Silting of rivers: With increased flooding and surface run-off moil soils and silt is washed into rivers, this can not only change local ecosystems (water temperature and clarity) but can also reduce the depth of rivers making navigation harder.

Silting of seas and oceans: With the increased frequency of flooding and landslides more silt gets washed into the oceans. The increased amount

drugs, including the basic ingredients for the hormone contraceptive pill, quinine (a anti-malaria drug) and curare (a paralysing drug).

Cash crops and agricultural products: Yam, coffee, rubber, mango, banana, sugarcane, cocoa and avocado were all first discovered in rainforests.

Ecotourism: With people becoming ever more environmentally conscious and looking for increasing adventures, ecotourism to rainforests is increasing. This not only helps protect rainforests, but creates income for locals. Ecotourism is an important income to countries like Costa Rica and Belize.

Home to indigenous groups: Although the number of indigenous groups and people have declined rapidly since colonisation in South America, it is estimated that there are still over 200,000 people that consider the Amazon their home.

Urban growth: With the world population increasing as well as rates of urbanisation increasing many cities like Manaus in Brazil are growing rapidly causing deforestation.

Population growth: As populations grow, particularly in countries like Brazil, Peru, India and Vietnam that contain rainforests the demand for land increases, both to grow food and to live).

Plantations: Primary products are often seen as an income source for LEDCs, many of who have large areas of rainforest. At the same time with fossil fuels running out, alternative fuels sources are been searched for including biofuels e.g. Palm oil. This has lead to widespread deforestation in countries like Malaysia and Indonesia to plant cops like palm oil.

Timber (hardwoods): Hardwoods like mahogany and teak that take hundreds of years to grow are still in high demand to make things like furniture. The extraction of these trees can kills trees around them. Also many countries like China are also demanding large amounts of normal timber that are not always taken from sustainable sources.

Hunting: Hunting takes two forms, one form is for bushmeat to feed families and enough the sale of animals either alive e.g. parrots or dead for their skins e.g jaguars.

of silts reduces the transparency of the sea reducing the light reefs receive and the temperature of the water. Increased silt can also block important shipping lanes.

Breaking of nutrient cycle: The top soil of rainforests is very thin an receives the majority of its nutrients from rotting flora and fauna. Be removing trees you also remove animals and therefore the source of the soils nutrients. With increased erosion the top soil (humus) layer is quickly washed away.

Sandification/desertification: Because rainforest soil loses its fertility very quickly after deforestation it quickly becomes hard to grow any vegetation on it, leading to sandification and possibly desertification.

Loss of indigenous homes: By clearing rainforests you are obviously destroying the homes of indigenous groups. But also moving close to indigenous groups can spread disease and alter local culture and traditions.

Reduced rainfall: Deforestation can lead to reduction in local rainfall because less water is intercepted and transpired from vegetation into the atmosphere reducing the formation of clouds and rainfall.

Deserts – Sahara Desert, Northern AfricaDistribution of Deserts

Deserts are located near the tropics (Tropic of Cancer and the Tropic of Capricorn)

Desert Climates

Deserts are extremely dry (arid) places. True deserts normally have less than 250mm a year. Deserts are very dry because the air that descends over them is very dry. The air is dry because most of the moisture has fallen as precipitation over the Equator (tropical rainforests) before being pushed out and falling near the tropics. The air is also very dry because the air travelling from the equator to the tropics travels over land and not the sea. This means that no additional moisture is picked up. Because there is no moisture in the air, there are very few clouds in deserts which means desert areas are exposed to high levels of incoming radiation from the sun. This means that daytime temperatures in the desert are very high. However, the lack of cloud cover also means that a lot of outgoing radiation is able to escape, making desert temperatures very cold at night. So even though the annual temperature range in deserts is very low, the daily temperature range is very high. The daily temperature range is known as the diurnal temperature range.

Desert Fauna and Flora

Because of the very arid conditions found in deserts, both plants and animals have had to adapt to survive. Adaptations include:

Succulents e.g. cacti: Succulents tend to be fairly fat fleshy plants that are able to store water in their leaves, trunks and roots.

Ephemeral: These are plants with very short life cycles - typically 6-8 weeks. This means that they can take advantage of very short wet seasons in order to pollinate.

Long and wide roots: Plants in deserts have very long roots so that they are able to absorb the maximum amount of rainfall during periods of rainfall. It also makes them more stable in very lose soil.

Spiky and waxy surface: Many plants like cacti protect themselves with spikes and wax so that they are not eaten or damaged by animals.

Deserts don't have the same variety of animals as tropical rainforests, but many insects, reptiles and mammals have adapted to survive.

Nocturnal: Many animals will hide in burrows or behind rocks and vegetation during the hot daylight hours and only emerge at night.

Camels: Camels store fatty tissue in their humps which when metabolised actually releases water as well fat enabling them to survive in deserts.

Desertification – Sahel The Sahel is an area of land south of the Sahara, running from Mauritania in the west, through Niger, Burkina Faso, Mali, Chad, Sudan and across to Ethiopian in the west. The Sahel is roughly 5,400km long and covers an area of about 3 million km2. The Sahel receives between 200mm and 600mm of rain annually. The vegetation is mainly savanna (grassland) with some areas of woodland and shrub land. The people of the Sahel are traditional semi-nomadic herders. In recent years the Sahel has been suffering from increasing soil degradation and desertification. The main reasons for increasing soil degradation are:

Population Growth (the population of the region is growing at about 3% a year and doubling every 20 years)

Deforestation (much of it caused by people collecting firewood) Overgrazing (some of this is caused by loss of land to National Parks and

tourist developments and commercial farms) Colonialism - the creation of borders forced people more into villages making

them less nomadic and placing greater pressure on the land. Rising temperatures (greater evaporation) and reduced rainfall (droughts) Storms - the rainfall that does take place tends to be in shorter more intense

storms that can lead to water erosion.

Human Causes of Desertification Physical Causes of Desertification

Overgrazing: Allowing too much livestock to graze on a piece of land which means all the vegetation is eaten making the ground susceptible to wind and water erosion.

Overcultivation: If you farm land to intensively and don't have fallow periods then all the nutrients in the soil get used.

Deforestation: Cutting down trees which not only means the land will be receiving less nutrients, but it also means it is more vulnerable to erosion because there is no interception and less stability because the root systems have been removed.

Overpopulation: As the world population continues to grow (now about 7 billion) the demand for agricultural products (crops and meat) is increasing, causing more land to be deforested, overcultivated and overgrazed.

Rising Temperatures: As global temperatures increase it is becoming increasingly hard for vegetation to grow thus reducing vegetation cover and increasing the risk of wind and water erosion.

Falling Rainfall: As the amount of rainfall reduces in some areas like the Sahel, then it is increasingly hard for vegetation to grow again making the ground more vulnerable to wind and water erosion.

Flash floods: Intense periods of rainfall can also cause erosion of topsoil which leads to land degradation.

Fertiliser and Pesticide Use: By using fertilisers and pesticides you can artificially increase yields of crops. However, the process is unnatural and prolonged periods of use can all naturally produced nutrients to be used and local water sources to become polluted reducing the ability of land to cultivate crops and therefore making it vulnerable to chemical degradation as well as wind and water erosion.

Unsustainable Water Use (aquifer depletion, unsustainable irrigation): If aquifers or rivers are used unsustainably then areas can become increasingly arid as water resources are used up. A classic example of unsustainable irrigation happened in the Aral Sea.

Toyotarisation: This is basically the increased use of 4x4s to travel across grasslands, deserts, etc. damaging topsoil and increasing wind and water erosion.

Wind: If a region is particularly windy then the amount of wind erosion is likely to increase.

Problems Caused by Desertification Solutions to Desertification

Dust Storms: As soil become less stable because of the lack of vegetation it become much more vulnerable to wind erosion which can create large scale dust storms. Northern China is suffering from an increased frequency of dust storms as desertification takes place south of the Gobi Desert.

Reduced Crop Yields: As the soil becomes less fertile the amount of crops that it can support will reduce. The falling crop yields can lead to famine and starvation.

Conflict: With increasing soil degradation and reduction in agricultural output and available agricultural land conflict can arise over diminishing resources.

Famine: If the soil become degraded and cops begin to fail or the yields reduce in quantity then famine can happen. Famine is normally caused by a combination of factors, soil degradation, drought and possibly a natural disaster or conflict, so if soil degrades it increases the potential of famine.

Crop Rotation and Fallow Periods: Growing different crops each year, so different nutrients are used and to allow periods of rest (fallow periods) so that soil can regain its fertility.

Shelter Belts: Shelter belts (sometimes called wind breaks) are areas of forest or hedge that are left untouched to protect farmland from the affects of water and wind erosion.

Reforestation and Afforestation: By reforesting or afforesting areas you can help return land to its natural state, making it more fertile and stable, thus reducing wind and water erosion and ultimately land degradation.

Irrigation: It is possible to water areas of land that have become arid to try and improve the productivity of the soil.

Grazing Quotas: Placing limits on the number and types of animals that can graze on land, reducing the destruction of vegetation and eventual desertification.

Population Control: The main reason we are putting more pressure on the earth's resources (including soil) is because the world's population has reached 7 billion and is still growing rapidly. If we can control population growth then we can limit the amount of agricultural land we need and the intensity of our farming.

GM Crops: GM stands for genetically modified. GM crops can be engineered to withstand poor soil and water shortages. By growing some types of vegetation you maybe able to add nutrients back to the soil.

Plate Boundaries – Various ExamplesType of Plate Boundary

Types of Crust

Direction of Movement

Major Landforms Tectonic Activity Example

Constructive Oceanic and oceanic

Away from each other (divergent)

Ocean ridges and islands

Small earthquakes and volcanoes

Mid atlantic ocean ridge (Eurasia vs North America)

Destructive Oceanic and continental

Towards each other (convergent)

Fold mountains (with volcanoes) and ocean trenches and island arcs if boundary at sea

Big earthquakes and big volcanoes

Andes Mountain Range, Chile and Peru (Nazca vs south American)

Collision Continental and Continental

Towards each other (convergent)

Fold mountains and mountain roots

Big earthquakes Himalaya, India, China, Nepal etc (Indo-Australian, Eurasian)

Conservative Continental and Continental

Alongside each other (transform)

No major landforms are found

Big earthquakes St. Andreas Fault, California, USA (Pacific, North American)

Earthquakes – Catania 1682 The 1693 Sicily earthquake struck parts of southern Italy near Sicily, Calabria and Malta on January 11 at around 9 pm local time. This earthquake was preceded by a damaging foreshock on January 9. It had an estimated magnitude of 7.4 on the moment magnitude scale, the most powerful in Italian history, and a maximum intensity of XI (Extreme) on the Mercalli intensity scale, destroying at least 70 towns and cities, seriously affecting an area of 5,600 square kilometres (2,200 sq mi) and causing the death of about 60,000 people. The earthquake was followed by tsunamis that devastated the coastal villages on the Ionian Sea and in the Straits of Messina. Almost two thirds of the entire population of Catania were killed.

Living Near Earthquakes:

Poverty: Some people are very poor and are forced to live on marginal land that is very vulnerable to the impacts of earthquakes:

Inertia: Some people have lived in earthquake zones although their life and are unwilling to move

Infrequency: Major earthquakes happen relatively infrequently so some people are prepared to take the risk and don't think that one will occur in their lifetime.

Overpopulation: Some countries are very densely populated so people are forced to live on dangerous and marginal land.

Building Design: Building design has improved and now people are confident that their house or workplace will withstand strong earthquakes.

Education and preparation: Many countries practice earthquake drills and evacuation and prepare their houses so feel confident that they will know what to do in an earthquake.

Economic Opportunities: Many tectonically active locations have good resources and locations e.g. next to the sea. Because of this there are many job opportunities which people move near to take advantage of.

The affect an earthquake has on humans can depend on numerous human and physical factors. These factors include:

The depth of the earthquake

The magnitude of the earthquake

The duration of the earthquake

The local geology (soft or hard rock, solid or cracked rock)

The location of the epicentre (in a rural or urban area)

The population density around the epicentre.

The building design and hazard mapping near the epicentre.

The time of day (earthquakes at night might trap people in their houses, earthquakes during dinner time might trigger more fires).

The preparedness of the population (evacuation routes, emergency services, etc)

Building Design and Building Preparedness

Buildings can be made safer in a number of ways. Firstly they can be built in areas less vulnerable to hazards e.g. flat land with solid rock. They can then be designed to be made stronger, cross braces can be used to make the building stronger, dampers can be added to high buildings to counteract swing in earthquakes or even springs can be added to foundation to allow buildings to move. Once a hose is built pictures can be secured to walls, windows reinforced and emergency exits created. Read the attached booklets to see how the American government recommends schools and houses to prepare.

Volcanoes – Mt. Etna, Sicily, ItalyMount Etna is an active stratovolcano on the east coast of Sicily, Italy, in the Province of Catania. It lies above the convergent plate margin between the African Plate and the Eurasian Plate. It is the tallest active volcano in Europe, currently 3,329 m high, though this varies with summit eruptions. It is the highest mountain in Italy south of the Alps. Mount Etna is one of the most active volcanoes in the world and is in an almost constant state of activity. The fertile volcanic soils support extensive agriculture, with vineyards and orchards spread across the lower slopes of the mountain and the broad Plain of Catania to the south.

Dangers of Volcanoes:

Lava Flows: Most traditionally associated with volcanoes, but probably one of the least dangerous hazards to humans. Lava flows only travel up to a couple of km/hr so it is possible to move out of their way. However, they can bury and incinerate any land or property that they travel over.

Pyroclastic Flows: These are giant clouds of ash and gas. They are extremely dangerous because they can travel up to 500 km/hr, reach distances of 30km and can be over 700 degrees centigrade in temperature. They will burn, knock over or bury anything in their path.

Lahars: These are a secondary hazard and normally occur on snow covered volcanoes. Hots ash and gas melt the snow and then mix. They then travel down the volcano as a fast moving mudflow which can drown or bury anything in their path.

Ash Clouds: Not as fast moving as a pyroclastic flow, but ash clouds can still be very disruptive. The weight of falling ash can collapse buildings and destroy crops. They can reduce sunlight by blocking out the sun and even cause problems for air travel like the recent Iceland volcano.

Lava or Volcanic Bombs (tephra): When volcanoes erupt they often throw out semi molten pieces of rocks. As long as humans are a safe distance they don't really pose any problems. However, because of their heat they can start fires.

Poisonous Gases: When volcanoes erupt they can release poisonous gases like carbon monoxide and sulphur dioxide. These can kill humans or animals if they are too close, but they can also contribute to the greenhouse effect.

Predicting an eruption:

Change in the shape or size of volcano Change in the temperature of a volcano Change in the amount and type of gases being released Earthquake activity Changes in plant and animal life Changes in local hydrology e.g. temperature and chemical composition of

nearby rivers.

Living Near Volcanoes

Minerals, it is possible to mine minerals like sulphur from volcanoes Geothermal potential (cheap and clean renewable energy) e.g. Iceland and El

Salvador Tourism - tourists like to view and walk up volcanoes e.g. Mt. Etna There is often hot springs near volcanoes which tourists and locals can enjoy

e.g. Mt. Arenal in Costa Rica or the hundreds of onsens in Japan. Land around volcanoes is very fertile because of all the minerals, therefore

many people choose to farm the land. Poverty, people simply can't afford to live anywhere else apart from the

marginal land on volcanoes Complacency or naivety because the volcano has not erupted for a long time. Confidence that they will be given adequate warning to evacuate Family home. Family have always lived in the area and don't want to leave Shortage of space and high population density. San Salvador is slowly

growing up El Boqueron because of the shortage of space. Their beauty, places like Mount St. Helen's are beautiful to look at and enjoy.

MECDs vs LECDsComparing Vulnerability to Hazards in MEDCs and LEDCs

Preparedness and Vulnerability in MEDCs Preparedness and Vulnerability in LEDCs

Many MEDCs do hazard mapping and zonal planning. They will assess the risk for different areas of the country e.g. is it likely to flood or be in a lava flow. They will then only allow low value and low risk land uses in hazardous areas.

Most MEDCs have fairly strict building codes to protect against earthquake damage. Buildings will have to be reinforced, have shatter proof windows, dampers, sprinklers and escape routes.

In MEDCs the entire population will be educated about hazards. They will know what potential hazards there are and how to respond to them. People will be told evacuation routes and where safe areas are.

Emergency and rescue services will be trained so they know how to find victims and how to treat them. They will have proper equipment and carry out practices.

LEDCs tend to have more informal settlements that don't follow building codes. This makes them more vulnerable when hazards hit.

Many LEDCs suffer from rapid urbanisation and uncontrolled growth of settlements on dangerous marginal land.

Medical care will be poorer in LEDCs and there will be less money spent on search and rescue teams.

Many LEDCs rely on emergency aid during times of natural disasters. Emergency aid always takes several days to mobilise which will usually cost lives.

Transport and communication will be poorer in LEDCs. Much of the population will not have access to phones, television or the internet so will not be warned about forthcoming natural disasters.If they do know, lack of adequate transport may make escape difficult. There will certainly be a shortage of helicopters.

There probably won't be adequate supplies of tents,

Hazards will be better monitored in MEDCs, scientists will study volcanoes, track hurricanes and then try and make accurate predictions and inform the public.

Transport and communications are usually much better. The population can be informed and are more easily able to escape. There are likely to be more helicopters which can be essential in search efforts when roads are damaged.

MEDCs are simply richer so they can afford to spend more money on training and preparedness.

There will be stockpiles of tents, blankets, food and water for anyone who has lost their home and possessions.

blankets, food and clean water.

Services like electricity and water will take longer to repair, leading to the secondary hazards of diseases and exposure.

A lot of population will be illiterate and never taught about potential natural disasters and how to respond to the natural disasters.

Less money will be spent on monitoring potential hazards, because countries have less money and less trained scientists.

Evacuation routes may not exist and there may be as shortage of shelters.

Poor LEDC cities often have very high population densities. This causes more people to be effected by the primary and secondary hazard.

WeatheringTypes of Chemical Weathering

Carbonation or solutionThis is caused by carbonic acid which occurs naturally in rainwater. Although only a very weak acid, it chemically reacts with rocks such as limestone and slowly dissolves them. Areas that have standing rainwater are going to experience higher rates of carbonation, therefore it is less likely to happen in dry countries and on steep slopes. The dissolved rock then gets washed away.

OxidationThis occurs when iron compounds within rock, reacts with oxygen to produce a reddish-brown coating.

HydrolysisHydrogen in water reacts with minerals in the rocks. Instead of dissolving the rock, the water actually combines with the rock. One example of hydrolysis is feldspar found in igneous rocks such as granites can be turned into a form of clay.

HydrationCertain rocks are able to absorb water into their structure, causing them to swell (get bigger). This not only exerts pressure because of the growing size but causes the chemical structure to change.

Types of Physical (mechanical) Weathering

Freeze-thaw or Frost ShatteringThis occurs in areas with moisture and a high diurnal (daily) temperature range that falls below zero. As water freezes it expands placing pressure on the rock around it. When it thaws more water is able to enter the crack and then it is able to freeze again. This process continues, slowly breaking down the rock.

Exfoliation or Onion WeatheringAgain this tends to happen is areas with a high diurnal temperature range (very hot in the day and cold at night). During the day rock heats up and expands and during the night it cools down and contracts. These changes in temperature and shape cause the rock to weaken and layers beginning to peel off, just like an onion.

Pressure ReleaseWhen rocks above are weathered, or eroded and then removed, rock underneath experiences and reduction in pressure placed upon it. The removal of pressure allows the rocks to expand causing them to fracture. When a glacier melts a similar process happens.

Salt Crystal GrowthCommon in hot areas with high rates of evaporation. Water is evaporated leaving behind salt crystals. The salt can attack the rock chemically, but they also expand placing pressure on the rocks structure.

Factors Affecting the Rate of Weathering

Geology: The type of rock, is extremely important in affecting rates of weathering. Rocks with cracks are more likely to experience increased rates of physical and chemical weathering. Cracks allow water to get. Soft rocks are much more vulnerable to weathering than strong rocks. Also the chemical composition of rocks is also important. For example limestone's that have large amounts of calcium carbonate are more vulnerable to carbonation.

Vegetation: Areas of land that have vegetation are more likely to experience rapid biological weathering. However, they are also likely to insulate the rock from large temperature ranges, reducing some physical weathering. Vegetation will intercept rainwater, reducing rates of some chemical weathering. Vegetation can hold rain water in-situ though increasing chemical weathering and some mosses contain chemicals that can increase chemical weathering.

Climate: Climate is very important because hot temperatures increase the rates of chemical reaction, therefore increasing chemical weathering. Areas with high diurnal temperature ranges will see an increase in some physical weathering. Wet areas are going to see an increase in chemical weathering. Wet and warm areas are also likely to see an increase in the amount of vegetation, increasing biological weathering.

Relief: A steep relief can increase some forms of physical weathering, but can slow chemical weathering. Most forms of chemical weathering need rain to be stationary, but steep slopes encourage fast surface run-off. However, a steep slope will cause weathered rocks to fall away quicker exposing fresh rock beneath to be weathered.

Aspect: This is the direction a slope is facing. The direction it faces can affect the amount of sunshine it receives. If a slope is facing the sun it might have more vegetation growing on it, increasing biological weathering. If it is not facing the sun it might have less vegetation increasing the rates of chemical weathering and physical weathering.

Humans: Humans can influence rates of weathering in many ways, they can add chemicals to water courses, they can deforest or forest areas, they can introduce animals or remove animals.

Why is weathering more rapid in tropical areas than temperate areas?

Briefly tropical areas tend to experience more weathering because of :

Large amounts of rainfall increasing chemical weathering

Large amounts of vegetation increasing biological weathering

They are nearer to the equator so there are high temperatures and faster rates of chemical reaction

Some areas (high areas and desert areas) have higher diurnal temperature range.