The continents are still drifting apart. But how do we know that they are moving? They move slowly that you and I cannot see it.

 However, nowadays we have human- made satellites in space, which can measure even very small movements on earth. The satellites give us very accurate measurements of the movements of the continents.

 We now know New York is moving about 2.5 centimeters farther away from London every year! South America is moving 20 centimeters father from Africa every year. On average, continents move at about the same rate as a fingernail grows.

 But why do the continents move? And how do they move? Imagine the earth as something like an egg –it has many layers. At its centre, the earth is solid-and very, very hot!

 Around this solid center is a liquid layer. This liquid layer is also very hot. It is made up of melted rock-that is, rock which has become liquid because of the heat.

 Above this is a thick layer, which is solid. It is also cooler. On this solid crust are the continents and oceans.

 Now, the liquid layer is always boiling. There are currents in it, which are like the currents in the sea.

 Because of these currents, the solid crust broke into pieces. Scientists call these pieces `plates’.

 Our continents and seas are on these plates. But these plates are always moving and hitting each other. And when these plates move, the continents also move.

 What will the continents be like, in the distant futures? We know that America is moving away from Europe, and closer to Asia. The Atlantic Ocean will continue to become wider, and the Pacific Ocean will become narrower.

 Maybe in another 200 million years there will be no need to cross the ocean from America to Asia. America will have touched Asia. And people will be able to walk across!

 But will there still be people on earth, in that distant future?