The Four Layers of Earth
The Earth is composed of four different layers. Many geologists believe that as the Earth cooled the heavier, denser materials sank to the center and the lighter materials rose to the top. Because of this, the crust is made of the lightest materials (rock- basalts and granites) and the core consists of heavy metals (nickel and iron).
-The Crust:The Earth's Crust is like the skin of an apple.
Those caused by movements of the Earth. These occur with the minimum amount of warning and include earthquakes, volcanic eruptions and tsunamis. They are difficult to predict and impossible to stop. All that can be done is to take appropriate action to limit damage and loss of life after they occur.
Weather related disasters. These will include hurricanes, tornadoes, extreme heat and extreme cold weather. There will usually be some degree of advanced warning, but since weather is unpredictable, nothing can be done to stop these disasters from developing once the weather system develops. Again, in areas prone to this sort of disaster, some provision can be made to limit damage and loss of life.
Floods, mudslides, landslides and famine. These are usually the consequence of extreme weather events, or are supplementary to other natural disasters.Often they are the result of extreme and unforeseen conditions.