Hazourdous Environments

Hazard

an event which has the potential to cause harm to the environment, people, or economy.

Examples of Tectonic and geological hazards:

Earthquakes, volcanic eruptions, landslides, tsunamis.

Examples of Climatic and meteorological hazards

Storms, floods, droughts, tornadoes.

Examples of Biological hazards

Pests, diseases.

How can natural hazards categorized

Magnitude, frequency, size, duration, location.

Tropical Cyclones

Rotating, low-pressure systems with heavy rainfall, high wind speeds, high waves, and storm surges.

Cyclone location and measurement

Occur in tropical regions between 50-300 north and south of the equator, measured on the Saffir-Simpson Scale.

Earthquakes

Sudden, violent shaking of the ground caused by tectonic plate movement and the buildup of pressure

Where do earthquakes occur and how are they measured?

• Occur at all types of plate boundaries

• epicenter directly above the focus

• magnitude measured on the Richter scale or moment magnitude,

• damage measured on the Mercalli Scale.

What are volcanoes, where do they occur and how are they measured?

• Magma erupting onto the Earth's surface as lava

• most occur at constructive and destructive plate boundaries

• magnitude measured by Volcanic Explosivity Index (VEI).

Causes of Tropical Cyclone Hazards:

• Low pressure

• sea surface temperatures over 27°

• between 50 and 200 north and south of the equator, low wind shear, deep layer of humid air.

Formation of a tropical cyclone

1. Warm moist air rapidly rises forming an area of low pressure

2. air from high-pressure areas rushes in to take place of the rising air

3. this air then rise → continuous flow

4. as air rises, it cools and condenses releasing heat energy which powers the cyclone

5. Coriolis force causes the air to spiral around the center

6. some air sinks in the middle → calm eye

7. cyclone moves westward.

Coriolis force

The force created by the rotation of the Earth.

Features of a tropical cyclone

• Heavy rainfall

• high wind speeds,

• storm surges,

• calm eye,

• highest winds and heaviest rain in the wall of the eye,

• diameter up to 800 km.

what are the 4 Plate boundaries?

• Constructive (divergent),

• destructive (convergent),

• collision,

• conservative (transform).

Constructive (divergent) plate boundary

• Plates moving apart,

• example:Mid-Atlantic ridge,

• volcanoes and earthquakes can occur.

Destructive (convergent) plate boundary

• Plates moving towards each other,

• denser oceanic plate subducts under less dense continental plate,

• volcanoes and earthquakes can occur

• example: Boundary between Nazca + American

Collision boundaries

• Plates of similar density moving towards each other, form fold mountains (no subduction)

• (e.g., Himalayas), causes earthquakes.

Conservative (transform) boundary

• Plates move past each other in opposite or same directions with diff speed,

• earthquakes occur.

Formation of volcanoes at constructive boundaries:

1. Plates moving away from each other, (these often occur under the sea/ocean)

2. lava escapes through the gap formed,

3. lava cools and hardens forming new crust,

4. runny lava leads to shield volcanoes with gentle sloping sides

Volcanoes at destructive boundaries

1. Plates move towards each other, heavier plate subducts,

2. friction causes heat and melting of plate material,

3. magma rises to the surface through cracks,

4. the cooling lava and ash builds up forming a volcano

   • lava is sticky and produces explosive eruptions here, these form composite/stratovolcanoes.

Formation of volcanoes at hot spots

1. Tectonic plate passes over a plume of magma at a hotspot,

2. magma rises to the surface through cracks in crust,

3. as the tectonic plate moves slowly over the magma plume, aline of islands may form (e.g., Hawaii).

Volcanic eruption primary hazards

• Ash,

• pyroclastic flow: clouds of super-heated material up to 700 degrees centigrade which can travel up to 500km

• lava flow,

• gas emissions,

• volcanic bombs.

Volcanic eruption secondary hazards:

• Lahars: when water (from melting snow + ice) mixes with volcanic ash to create fast-moving mud flows,

• acidification of water: sulphur emissions from eruptions increase the acidity of water

• landslides,

• climate change,

• fires,

• floods.

Formation of an earthquake

1. As tectonic plates move, the can get stuck due to friction

2. pressure builds up as the plates continue to try to move

3. eventually the plates jolt free along the fault line and the pressure is released as energy

4. the point at which the earthquake starts is the focus

5. the epicentre is the point directly above the earth

6. the energy passes through as tectonic waves

Depth of focus at a destructive (convergent) plate boundary

deep to shallow

Depth of focus at destructive (collision) plate boundary:

shallow

Depth of focus at constructive (divergent) plate boundary:

moderate to shallow

Depth of focus at conservative plate boundary:

shallow

Ring of Fire

A major area in the basin of the Pacific Ocean where a large number of earthquakes and volcanic eruptions occur.

Tectonic plates

Large, rigid pieces of the Earth's lithosphere that fit together like a puzzle and move due to convection currents in the mantle.

Fault line

A break or crack in the Earth's crust where tectonic plates meet and can slip past each other.

Focus

The point within the Earth where an earthquake starts.

Epicenter

The point on the Earth's surface directly above the focus of an earthquake.

What is the primary hazard of an earthquake?

ground shaking.

Secondary hazards of earthquakes?

• building collapse,

• landslides,

• mudflows,

• gas leaks,

• tsunamis,

• fires, soil

• liquefaction,

• subsidence.

Soil liquefaction

When loose materials, including soil and rocks, act like a liquid due to the shaking caused by an earthquake.

Subsidence

The sudden sinking of the Earth's surface.

Reasons for living in hazardous regions?

• lack of education: not aware of risks

• adv>disadv: fertile soil, trade, jobs, tourism, water, etc.

• too poor to move away

• born there (friends + fam)

• not frequent disaster

Economic factors that affect vulnerability to natural hazards?

• wealth, level of development,

• insurance,

• buildings,

• technology

Social factors that affect vulnerability to Natural hazards?

• population density : increased deaths

• education: increased wealth = safer housing

Physical factors that affect vulnerability to natural hazards?

• global location: increased hazards

• physical environment: steep slopes= increased landslides or coastal areas= tsunamis

Short-term impacts

Immediate effects or consequences of an earthquake, such as deaths, damage to infrastructure, displacement of people, and disruption of services.

Long-term impacts

Effects or consequences of an earthquake that persist or develop over a longer period of time, such as ongoing displacement, changes in building codes, infrastructure improvements, and changes in the natural environment.

Cyclone case study and it’s short and long term impacts:

Tropical cyclone Haiyan

• Philippines, Vietnam and Taiwan

• magnitude: 5

• 2013

Short term: 6400 deaths and 33 million cocnut trees destroyed

longterm: 4 million people still in shelters after a year and repairs caused 5.8 billion dollars

Earthquake case study and its short and long term impacts:

Gorkha Earthquake

• Epicentre: Nepal,, Barpak village

• Magnitude: 7.8

• 2015

Short term: 8600 deaths and roads blocked due to landslides

Longterm: repairs cost 10 billion USD and 70% of displaced ppl still in temp. shelters afetr 2 years

Volcano case study and its short and long term impacts:

Mount Meropi eruption

• Java, Indonesia

• Magnitude: VEI 4, composite volcano

• 2010

Short term: 353 deaths and pyroclastic flow travelled 3 km

Long term: 2500 residents permanently moved away and money given to farmers to replace lost live stock + crops

List methods of monitoring that help predict earthquakes:

• Tiltmeter : which monitors ground changes

• Clusters of small earthquakes

• Changes in radon gas emission

• Changes in animal behaviour

• Remote sensing of ground movement using satellites

State ways how countries can prepare for earthquakes?

• Building design and earthquake resistant structures

• Land use planning

• Earthquake drills

• Emergency planning

How can Building design be used to prepare for earthquakes?

• Shutter on windows prevent falling glass

• Cross-bracing of steel frames

• Foundations sunk deep into the bedrock

• Frames which sway away with the earthquake tremors

• Rubber shock absorbers to reduce tremors moving through the building

How can land use planning be used to prepare for earthquakes?

Planning can ensure that valuable services such as the fire service and hospitals are not built in high risk areas. Densely populated housing can be located away from high risk areas.

How can drills and education be used to prepare for earthquakes?

Drills help people prepare for what to do in an earthquake to protect themselves. Education about how to prepare homes means that people are less likely to be I jurd by falling objects and furniture.

How can GIS help prepare for an earthquake?

Geographic information systems (GIS) provide data such as vulnerable areas, land use and infrastructure. This can be used foot assist in land use planning.

Developing country, earthquake preparation case study:

Nepal, Kathmandu

Prep before earthquake: Nepal Red Cross society maintained 12 warehouses with stocks of emergency supplies

Isssues with prep: not enough for the scale of disaster

Developed country, earthquake preparation case study:

Japan

Prep before earthquake (2011): Over 80% of buildings in Tokyo are earthquake resistant

Issues with prep: Many buildings survived the earthquake but not the tsunami

What short term responses must be taken after an earthquake?

• Searching collapsed buildings to rescue people who are trapped

• Providing medical assistance

• Distribution of food and water

• Ensuring that people have shelter

Earthquake short term response, developing country case study:

Nepal

Three Chinook helicopters; 100 search and rescue; medical workers

Issue: too slow, epicentre not reached for 24 hours

Earthquake short term response, developed country case study:

Japan

Self Defence forces sent in immediately to organise food, water, shelter and medicines

How is Hazard mapping and GIS useful for long term planning?

• Identify the main roads into areas for emergency aid

• To inform land use zoning so hospitals etc... are not built in vulnerable areas

• To coordinate all the agencies involved when there is a hazard event

• To identify if there a link between vulnerability and risk

Rebuilding programmes:

• Large scale rebuilding is often required after an earthquake event

• Existing buildings and structures, such as bridges, can be retrofitted to make them safer in future events