In this document you are going to get exposed to a summary done by me. This will help you to clearly understand how our earth works and what are the natural hazards. Earthquakes, volcanoes and tsunami's, how do they happen and what are the primary and secondary impacts of these natural hazards.

1. How did the layers form?
Some time after Earth formed, it got so hot that
everything inside it melted. The heavier substances in the
liquid sank, and the lighter ones rose, making layers. As
Earth cooled, the layers remained.
 The upper mantle is about 600 km thick
 The lower mantle is about 2300 km thick
 Together the crust and the upper mantle form a hard and rigid layer called
the LITHOSPHERE

2. How does an Earthquake happen?
 An earthquake is the sudden, violent shaking of the ground
 When tectonic plates move, they can become locked together causing
stress and pressure to build. Eventually, the stress becomes so great
that the rocks fracture and the pressure is suddenly released
 This causes intense ground shaking for seconds to minutes
 The focus is the point at which the earthquake starts below the Earth's
surface
 The epicentre is the point on the Earth's surface directly above the focus
 The magnitude of earthquakes is measured on the Richter Scale
 As the shock setteles into it’s new position (after the movement of the
tectonic plates) there will be lots of smaller earthquakes called
Aftershocks

3. Impacts of the Earthquake:
Short Term Impacts Long Term Impacts
Deaths and Injuries Financial cost
Tsunami is most probably expected to
come
Houses, health centers and schools rebuilt
Roads blocked due to landslides Displaced people still in temporary shelters
Houses, schools and health centers
destroyed and damaged
Water mains bursts, no more water left
When an earthquake occurs beneath the sea bed this can lead to a tsunami
 As the sea bed jolts, water is displaced and forced upwards creating a
wave
 As the waves approach the land they slow and the wavelength becomes
compressed
 This leads to an increase in wave height: they frequently reach 5-10
meters, but can reach 30 meters
 It can travel at over 700 km an
hour
 As they reach shallower water
near a coast they get slower and
taller, this makes them deadly
and destructive

4. How does a Volcano happen?
 Volcanoes occur at divergent (constructive), convergent (destructive)
plate boundaries and do not occur at collision or transform boundaries
Volcanoes at divergent boundaries:
 At a divergent the tectonic plates are moving away from each other
 It often occur under the sea/ocean
 The lava escapes through the gap left as the plates move apart
 The lava cools and hardens forming a new crust

5. Impacts of the Volcanoes:
Primary impacts Secondary impacts
Social
 Deaths and injuries
 Displacement of people
 Damage to properties and
infrastructure
 Mental health issues e.g. stress,
anxiety, depression
 Homelessness
 Disruption to services such as
healthcare and education
Economic
 Significant costs for repair and
reconstruction
 Loss of income and employment
 Costs of immediate responses
 Slower economic growth and
development
 InIncreased costs of insurance and
hazard management strategies
 Disruption of trade and economic
activity
Environmental
 Poor air and water quality
 Loss of biodiversity
 Destruction of habitats and
ecosystems
 Acid rain can damage ecosystems
 Release of greenhouse gases can lead
to a rise in global temperatures