Saturday, January 5, 2008

Inside the Earth

The centre of the Earth is very hot. This heat produces enough energy to keep the ground under your feet constantly moving as the major land masses, or continents, are carried slowly along on a lower layer of semi-liquid rock. This movement causes the continents to be pulled apart in some places, creating new oceans. In other places, they collide and create mountain ranges.

A shifting world
Scientists have discovered that around 250 million years ago all of today's main continents were joined together. Animal alive at that time, such as the dinosaurs, were able to move freely across this huge single landmass. By 200 million years ago, it was starting to break up.

What is the Earth made of?
The Earth has an outer layer of solid rock called the crust (5-60 km/3-37 miles thick), a middle layer of hot, semi liquid rock called the mantle (2900 km/1800 miles thick), and a very hot liquid centre, the core (3470 km/2160 miles in radius). Inside the Earth, the temperature increase rapidly towards the centre, where it is nearly as hot as on the surface of the Sun.
The solid crust is broken into pieces, called plates, which float on the mantle. Some plates are covered by oceans, others by the continents. The plates fit together like a jigsaw, and the places where they meet are called plate boundaries. In some places, two plates push together and one slides over the top of the other. Along some boundaries under the ocean, the plates are moving apart.

250 million years ago
North and South America, Europe, Asia, Australia and the Antarctic formed one big continent called Pangaea. The rest of the Earth was covered by an ocean called Panthalassa.

135 million years ago
Africa and South America began to split apart as the South Atlantic opened up. The North Atlantic formed between North America and Europe.

Tag :Earth inside
Tag :shifting world
Tag :Earth made