PLANET EARTH

Wednesday, November 4, 2009

Buried deep in the heart of our planet is a metal core of iron and nickel that is large than the Moon and almost as hot as the surface of the Sun. The outer layer of the core is liquid metal, but at the center enormous pressure has compressed it into a solid. When the Earth formed 4.6 billion years ago, it glowed red-hot, and the molten metals sank to its center while the lighter rocks floated to the surface.

A thick layer of the hot rock called the mantle, is wrapped around the core. This acts like a heated blanket, holding in the warmth. Around the mantel is a third layer called the crusts, which forms the rock surface of the Earth on which we live. The thickest parts of the crust are about 37 miles (60 km) deep, but if the Earth were compared to an apple, the crust would only be as thick as the apple’s skin.

The mantle contains traces of radioactive uranium, which steadily gives out heat. This warmth rises, creating a more fluid part of the mantle known as the asthenosphere. Above the asthenosphere lies the lithosphere, which includes the outermost mantle and the crust. The lithosphere is made up the massive plates that float on the fluid asthenosphere. These plates are constantly moving, causing the contenents to drift apart, mountains to form, the Earth to shake, and volcanoes to erupt.