Natural and Man-made Disasters with Case Studies
ICSE Class 8 · Geography · Chapter 5
What this chapter covers
- Disasters: meaning
- Natural disasters: floods, earthquakes, cyclones and droughts
- Man-made disasters: fires and oil spills
- Case study: floods in Assam and Bihar
- Case study: the Nepal earthquake
- Case study: oil spills on the coasts of the United States
- Preventing disasters: lessons from the case studies
Key points
- A disaster is an event that causes great loss of life, property or the environment and is beyond a community's own power to cope with.
- A hazard becomes a disaster when it strikes vulnerable people and places.
- Natural disasters, such as floods, earthquakes, cyclones and droughts, are caused by forces of nature; man-made disasters, such as fires, oil spills and gas leaks, are caused by human action or failure.
- Human actions like cutting forests and building in unsafe places can make natural disasters worse.
- Floods in Assam come from heavy rain, snowmelt and a silt-laden, braided Brahmaputra; floods in Bihar come mainly from the shifting, silt-laden Kosi and other Himalayan rivers.
- The 2015 Nepal earthquake (magnitude about 7.8, epicentre in Gorkha) was caused by the Indian Plate pushing under the Eurasian Plate; weak buildings made it deadlier.
- The Exxon Valdez (Alaska, 1989) and Deepwater Horizon (Gulf of Mexico, 2010) spills were caused by human error and harmed wildlife, fisheries and tourism for years.
- Many disasters can be prevented or reduced through forest protection, safe buildings, fire safety, strict rules for oil transport, early warnings and mock drills.
Questions answered
What is the difference between a hazard and a disaster?
A hazard is a condition that has the power to cause harm, such as a weak riverbank or a fault in the Earth's crust. It becomes a disaster only when it strikes people and places that are not ready for it and causes losses the community cannot handle on its own.
Give two examples each of natural and man-made disasters.
Natural: floods and earthquakes (also cyclones and droughts). Man-made: building fires and oil spills (also gas leaks and building collapses).
Explain how human actions can make floods worse.
Cutting forests on slopes lets water run off faster and sends soil into rivers, raising their beds. Filling wetlands and blocking drains leaves nowhere for the water to go, and weak embankments can break and flood large areas.
Why is drought called a creeping disaster?
It builds up slowly over weeks or months of poor rain, instead of striking in a single day as a flood or earthquake does.
Distinguish between the focus and the epicentre of an earthquake.
The focus is the point inside the Earth where the earthquake starts. The epicentre is the point on the surface directly above the focus.
Give two reasons why the Brahmaputra floods Assam so often.
It receives very heavy monsoon rain and snowmelt from steep tributaries, and it carries so much silt that its bed rises and it spreads into many channels with loose banks.
Why is the Kosi called the Sorrow of Bihar? What happened in 2008?
The Kosi carries a huge load of silt, changes its course and floods north Bihar often. In August 2008 its eastern embankment broke near Kusaha in Nepal, and the river flowed into an old course, affecting around three million people.
Explain the cause of the 2015 Nepal earthquake.
The Indian Plate is pushing north under the Eurasian Plate. The rocks along the Himalayas were locked, so stress built up for a long time until they suddenly slipped under central Nepal, releasing energy as an earthquake.