Restless Earth

The Structure of the Earth

The Earth is made up of four concentric layers:

Inner Core This is in the centre of the earth where it is hottest. It is solid and consists of Iron and Nickel with temperatures of up to 5,500C
Outer Core This is a liquid layer also composed of Iron and Nickel and is extremely hot with temperatures similar to the inner core.
Mantle This is the widest section of the Earth at approximately 2,900km. It is made up of semi-molten rock called magma. Towards the top of the mantle the rock is hard, but lower down nearer to the centre of the earth the rock is soft and beginning to melt.
Crust This is the thin outer layer of the earth which is only between 0-60km thick. The crust is the solid rock layer which we live on. There are two different types of crust:
  • Continental Crust: Carries land
  • Oceanic Crust: Carries Water
A diagram of the layers of the Earth

By Surachit [GFDL or CC-BY-SA-3.0-2.5-2.0-1.0 , via Wikimedia Commons

Diagram of the Earth's tectonic plates

Distribution of the Earth's Tectonic Plates

The Plate Boundaries

Destructive Constructive Conservative Collision

Volcanic Hazards

Shield Volcanoes Composite Volcanoes
Are found on constructive plate boundaries Are found on destructive plate boundaries
Are formed by eruptions of thin, runny lava which flows a long way before it solidifies Are formed by eruptions of viscous, sticky lava and ash that don’t flow far
Have gentle sloping sides and a wide base Have steep sloping sides and a narrow base
Contain basaltic magma which is very hot with low silica and gas content Made up of layers of thick lava and ash
Erupt frequently but not violently Contain andesitic magma which is less hot but contains lots of silica and gas
Erupt infrequently but violently, including pyroclastic flows (mix of ash, gases and rock)

Earthquake Hazard

There are two scales which are used to measure the magnitude (strength) of an earthquake.

  • The Richter Scale measure the amount of energy which is released from the earthquake.
  • The magnitude increases 10 fold as you move up the scale
  • The Mercalli Scale measures the effects or impacts and is measured in roman numerals I to XII.
Kashmir, 2005 California, 1989
75,000 dead Up to 12,000 homeless
75,000 injured 3757 injured
2.8 million homeless Built up, accessible area
Property damage $440 million Property damage $10 billion
Remote mountainous area 63 dead
Gas mains burst and fires broke out

Haiti - 7.0 on the Richter Scale

Primary Impacts Secondary Impacts
316,000 people were killed and 1 million made homeless 1 in 5 people lost their jobs because so many buildings were destroyed
250,000 homes and 30,000 other buildings destroyed or badly damaged they had to be demolished Hospitals became full very quickly
Transport and communication links were damaged Diseases, especially cholera became a problem
Hospitals (50+) and schools (1300+) were badly damaged People sleeping in streets for fear of more earthquakes.
The main prison was destroyed
Presidential palace was destroyed
Road blocked by rubble
Two years after the earthquake
  • 80% of the rubble had been cleared
  • 350,000 people still living in tents
  • Only 111,000 out of the 125,000 shelters planned had been built
  • Not all the money promised in aid had been sent, making recovery difficult
  • There is a shortage of safe, clean water
  • Only 18% of the required homes had been built

Managing Earthquake & Volcanic Hazards

Two years after the earthquake

The difficulties of predicting these hazards are that we don’t know…

However, there are things we can look out for.

Signs of a Volcano Nearing Eruption Earthquake Preparations
Animals and birds moving out from an area Create an exclusion zone around the volcano
An increase in gas emissions – When a volcano is close to erupting it starts to release gases such as sulphur. The higher the content of these gases, the closer it is to erupting. Make sure they have an evacuation plan
An increase in soil temperature – The temperature around a volcano will increase when it is about to erupt. We can use thermal imaging cameras to detect these heat changes Have an emergency supply of basic provisions such as food and water
The volcano swelling Ensure that money is available to deal with the emergency
An increase in small earthquakes – As the magma moves up through the cracks in the earth’s crust, many small earthquakes are set off. Ensure that a good communication system is in place
Water in ponds getting warmer Do earthquake drills so they know what to do in the event of a real earthquake
Build earthquake proof buildings. In San Francisco, the Transamerica Pyramid was designed to absorb the energy of an earthquake and withstand the movement of the Earth
Build roads and bridges to withstand the power of an earthquake

What is needed after a natural disaster - Case Study

Izmit Earthquake, 1999 What is needed
The Izmit earthquake struck 55 miles east of Istanbul, Turkey near the industrial city of Izmit Trained volunteers to help the injured people
It happened on August 17th at 3:02am local time and lasted 45 seconds. Clean water to prevent the spread of disease
The rate of urbanisation in Turkey had been rapidly increasing and with the huge amount of people in the city and lack of housing, people resorted to building their own houses. Food – shops, towns, roads and farms are often damaged
More than half the population in Istanbul is living in illegal accommodation says Turkey's Chamber of Commerce. Radio communication – phones often don’t work
So when the earthquake struck, it was these self-built houses and illegal houses which didn't meet building regulations that collapsed leaving people trapped in their houses. A plan to evacuate the area if necessary
Medical help

Immediate response and relief efforts

Criticisms of the Turkish Authorities