SMALL EARTHQUAKE
Every country in the world sits on top of large sheet of rock. Earthquakes are caused by the movement of these sheet of rock and measured by by the Richter Scale. Most earthquakes are just tremors which measure 3 or less on the Richter Scale. But each year there are about eighteen earthquakes which measure between 7 and 7,9. These are major earthquakes. The earthquakes that destroyed Kobe measured 7,2 on the Richter Scale. After the earthquake, geologists discovered a 60-kilometers fault line, where two sheets of rock had moved over 2 meters in opposite direction against each other.
The amount of damage caused by an earthquake depends on many things. A major earthquake can cause very little damage if it occurs far away from towns and cities. In Kobe, there were many building in a small space. Many of the buildings in Kobe were very old. They collapsed during the earthquake or were destroyed by the fire afterward. Although there are often earthquake in japan, Kobe was a frightening reminder of how much damage they can cause.
If they occur at the seabed with a bigger scale, e.g.7 or more on the Richter Scale, they can cause high waves called 'Tsunami'. If they happen, they may sweep the lives and everything away a long the coast lines and the plain area.
Example 2
CHANGE OF CLIMATE
Over millions of years world climates change. The way the have changed can be seen by looking at rock. In a particular area we might find beds of coal that were produced in a tropical swamp, or covered by sand stone that formed in a desert. These many covered, in turn, by mud stone deposited at the bottom of a shallow sea. Climate changes such as these take place over millions of year.
Extensive change of climate can take place over shorter periods of time. The ice ages that began 2 millions years ago-not along time in geological term-did not finish until 10.000 years ago. Throughout that time world's climate varied widely. At time much of the northern Hemisphere was choked with ice caps and glaciers. Then a few thousand years later, the climates were farmer than they are now. A few thousand years later still the glaciers swept southward again.
Even in historical times there have been major changes in the climate. On the Tassili plateu in the middle of Sahara Desert, there are of rock paintings showing grassland animals. They must have been painted when the local climate was much moister than it is now. Trees still grow nearby .They have immeasely long rots that extract water from deep rock. These trees could not have started growing unless there was water on the surface. During the thirteenth and fourteenth countries, Europe suffered “Little Ice Age”. The climate was much colder than it is now. In London, for example, winter fairs were often held on the frozen River Thames. This would be impossible now a day because it does not get could enough.
The change in climate through geological time, as revealed by the deferent rocks, can be the drifting of the continents from on climatic region to another. More recent changes are due to shorter-term events. Volcanic eruption can through up dust and gases such as sulfur dioxide high into the atmosphere. There they can block out sunlight and lower the temperatures on the Earth surface. A noticeable cooling in the 1960s coincided with increasing volcanic activity a cross the globe.
Another influence may be a fluctuation in the energy output of the sun itself. Old astronomical records show that the sun does,indeed, change in size and energy output from time to time. These changes alter the climate.
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