The Challenge of Natural Hazards PHYSICAL PAPER 1

Natural Hazard:

A naturally occurring process or event which has the potential to cause loss of life or damage to property.
Without people it is just a natural event not a hazard.

Hazard Risk:

The exposure of people to a hazardous event which may present a potential
threat to people or their possessions, including buildings and structures.

Vulnerability:

Is a place/person susceptible to physical or emotional injury

factors affect hazard risk: Urbanisation

-Urbanisation - Over 50% of the worlds population now live in cities. Densely populated areas are at the greatest risk.

factors affect hazard risk: Poverty

-Poverty - people may be forced to live in areas at risk. Shortage of housing leads to building on unstable slopes prone to floods and landslides.

factors affect hazard risk: Climate Change

Climate Change - A warmer world means an atmosphere with more energy creating intense storms and hurricanes. Wetter climates put areas at risk of flooding, and warmer drier climates put areas at risk of drought.

factors affect hazard risk: Farming

Farming - River floodplains have an abundance of fertile silt perfect for farming. Low lying countries are at a greater risk. Volcanic regions are also great for farming therefore people live within close proximity

Tectonic Hazards

- involved movement of tectonic plates in the earth's crust

- Atmospheric Hazards

those that form due to influences in the atmosphere

Geomorphological Hazards

- those that occur on the earth's surface

- Biological Hazards

- which involve living organisms

Theory of Plate Tectonics

The mantle that surrounds the core is made of solid material that can flow very slowly. The upper part of the mantle is
called the asthenosphere, which can deform like plastic.

the crust is split into tectonic plates - dense, thin oceanic crust, and thick,less dense continental crust. Together these form a rigid shell at the surface of the Earth called the lithosphere.

Theory 1: Convection

THEORY 1 CONVECTION: Circular movements of heat in the mantle
The cores temperature is 6000 ⁰C. This creates lots of energy and causes the magma to rise in the mantle from the core and then sink back to the core when it loses energy, as it cools closer to the crust.
The currents flow beneath the lithosphere, building up lateral pressure and carrying the plates with them.

THEORY 2: Slab Pull

Slab Pull: DESTRUCTIVE
At destructive plate margins the dense crust sinks into the mantle under the influence of gravity, which pulls the rest of the plate along behind it

THEORY 2 : Ridge Push:

Ridge Push: CONSTRUCTIVE
ocean ridges form high above the ocean floor. Beneath ocean ridges the mantle melts, the magma rises as the plates move apart and cools to form new plate material. As the lithosphere cools it becomes denser and begins to slide down, away from the ridge which causes plates to move away from each other.

Construct plate margin

Asthenosphere melts and hot magam rises. The plates are moved away- by slab pull, ridge push or combination of these. The magma rises in between and cools to form solid rock - which forms part of the oceanic. This plate sometimes fractures causing small nonviolent earthquakes. Much of the magma never reaches the surface - it's buoyant enough to push up the crust at margins to form a ridge and rift feature. Lava produced is runny: a volcano with a typically wide base and gentle slope known as a shield volcano is formed.

Example of Constructive Plate margin

Mid-Atlantic Ridge, Iceland

Destructive Plate margin

An oceanic and continental plate collides, the oceanic plate is subducted and sinks under the continental plate into the Earth's mantle: this creates a deep ocean trench. Hot magma rises up, some eventually erupt producing a linear belt of volcanoes. Magma becomes increasingly viscous as it rises to the surface, producing composite volcanoes which are steep-sided and have violent eruptions. Rock eventually fractures, causing earthquakes(violent ones).

Example of Destructive Plate Margin

Pacific and Philippine plate, ocean trench - Marian Trench.

Conservative Plate Margin

Tectonic plates move parallel to each other. Pressure builds up the margin of the plates as they're pulled along behind a plate being subducted elsewhere. Friction causes them to become stuck, the built-up pressure eventually the rock fractures in an earthquake. Volcanoes don't form at conservative plate margins as there are no gaps for magma to rise therefore no land is created or destroyed.

Example of Conservative Plate Margin

San Andreas Fault

Earthquake is...

a sudden and short period of intense ground shaking

FOCUS

The point where the pressure is released - the origin of the quake

SEISMIC WAVES

Shockwaves that spread out from the focus. The strength decreases with distance from the focus.

EPICENTRE:

The point on the Earth's surface immediately above the focus

INTENSITY

a measure of the violence of earth movement due to an earthquake.

MAGNITUDE

The actual size of an earthquake. Depends on the depth of the focus and the distance from the epicentre.

Primary Effect -

The immediate damage caused by a tectonic hazard. It can include death and destruction to property

Secondary Effect -

The unforeseen consequences of tectonic hazards such as fires, spread of disease and food shortages

Immediate Responses -

Search and rescue and keeping survivors alive by providing medical care, food, water, and shelter

Long-Term Responses -

Re-building and reconstruction, with the aim of returning peoples lives back to normal and reducing future risk

Earthquake in L'Aquila, Italy (2009)

On 6 April 2009, an earthquake measuring 6.3 on the Richter scale struck L'Aquila in the Abruzzo region of Italy (Figure 2.12). The earthquake's epicentre was seven kilometres northwest of L'Aquila.It struck at 3.32 a.m., so most people were asleep in buildings which collapsed.

Earthquake in L'Aquila, Italy (2009) : Primary effects

An estimated 308 people were killed,
1,500 were injured and 67,500 were made homeless.
Approximately 10,000-15,000 buildings collapsed, including: many churches, medieval buildings and monuments with considerable cultural value - the Basilica of St Bernardino, and Porta Napoli
■ San Salvatore Hospital, which was so severely damaged that patients had to be evacuated as it could not cope with injured victims
EU reported US$11,434 million of damage to L'Aquila.

Earthquake in L'Aquila, Italy (2009) : Secondary effects

-Aftershocks triggered landslides and rockfalls,causing damage to housing and transport.
-A landslide and mudflow was caused by a burst main water supply pipeline near the town of Paganini.The numbers of students at L'Aquila University has decreased.
-The lack of housing for all residents meant house prices and rents increased.
-Much of the city's central business district was cordoned off due to unsafe buildings. Some 'redzones' still exist, which has reduced the amount of business, tourism and income.

Earthquake in L'Aquila, Italy (2009) : Immediate Response

-For those made homeless, hotels provided shelter for 10,000 people and 40,000 tents were given out.
-Within an hour, the Italian Red Cross was searching for survivors. They were helped by seven dog units,36 ambulances and a temporary hospital. The British Red Cross raised £171,000 in support.
-The EU granted US$552.9 million from its Solidarity Fund for major disasters to begin rebuilding L'Aquila. The Disasters Emergency Committee (DEC),a UK group, did not provide aid because it considered Italy a more developed country

Earthquake in L'Aquila, Italy (2009) : Long-term Response

-Residents did not have to pay taxes during 2010. Mortgages and bills for Sky TV, gas and electric were suspended.
-Students were given free public transport, discounts on educational equipment and were exempt from university fees for three years.
-Homes took several years to rebuild and historic centres are expected to take approximately 15 years to rebuild.

Earthquake in Gorkha, Nepal (2015)

On 28 April 2015, a 7.8 magnitude earthquake struck the Gorkha district in Nepal (Figure 2.14). The earthquake's epicentre was in Barpak, 80 kilometres northwest of the capital, Kathmandu.Happened around 11:26 am - most people were out and about.

Earthquake in Gorkha, Nepal (2015): Primary Effects

-A total of 8,841 dead, over 16,800 injured and 1 million made homeless.
-Historic buildings and temples in Kathmandu including the iconic Dharahara Tower,a UNESCO World Heritage Site were destroyed.
destruction of 26 hospitals and 50 per cent of schools.
-A reduced supply of water, food and electricity.
352 aftershocks, including a second earthquake on 12 May 2015 measuring 7.3 magnitude.

Earthquake in Gorkha, Nepal (2015): Secondary Effects

-In 2014, the World Travel and Tourism Council reported that tourism was 8.9 percent of Nepal's GDP and provided 1.1 million jobs. It was expected to increase by 5.8 percent in 2015, but until Nepal has recovered from the earthquake, tourism, employment and income will shrink.
-The earthquake happened just before the monsoon season, when rice is planted. Rice is Nepal's staple diet,and two-thirds of the population depend on farming.Rice seed stored in homes was ruined in the rubble,causing food shortages and income loss.

Earthquake in Gorkha, Nepal (2015): Immediate Responses

-The UK's DEC raised US$126 million by September 2015 to provide emergency aid and start rebuilding the worst-hit areas. The Red Cross provided tents for 225,000 people.
-The United Nations (UN)health agency and the World Health Organization (WHO)distributed medical supplies to the worst-affected districts.
-Facebook launched a safety feature so people could indicate they were 'safe'. Several Companies did not charge for telephone calls.

Earthquake in Gorkha, Nepal (2015): Secondary Responses

-A recovery phase started six months later by the Food and Agriculture Organization of the United Nations (FAO). To expand crop production and growing seasons individuals were trained how to maintain and repair irrigation channels damaged by landslides in the earthquake.
-Nepal's government (along with the UN, EU, World Bank etc) carried out a Post-Disaster Needs Assessment. It reported that 23 areas required rebuilding, such as housing, schools, roads, monuments and agriculture.
-Eight months after the earthquake, the Office for the Coordination of Humanitarian Affairs (OCHA) reported that US$274 million of aid.
-The Durbar Square heritage sites were reopened in June 2015 in time to encourage tourists back for the tourism season. Mount Everest was reopened for tourists by August 2015.

Why do people live in areas at risk of Earthquakes?

• Major earthquakes happen relatively infrequently
• Planning and preparation reduces risk
• Many of the earth's natural resources (oil, minerals, and geothermal energy) are located near plate margins
so economic benefits outweigh the risks)
• Tourism/Job opportunities - in Nepal 1 million go trekking/mountain climbing a year and contribute $1.8
billion to the economy
• Wealth - do not have a choice

Monitoring/Prediction -

Attempts to forecast when and where a natural hazard will strike, based on current knowledge. Recording physical changes, such as earthquake tremors. (This can be done, but less reliable for earthquakes. It is difficult to predict their time, date and exact location).

Protection /MITIGATION-

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

Planning -

Actions taken to enable communities to respond to, and recover from, natural disasters, through measures such as emergency evacuation plans, information management, communications and warning systems.