Continents on the move

Continents on the move While all this was going on, the earth itself had not been inactive. Although the total volume of water in the oceans has not changed very much, the extent of the oceans has varied wContinents on the moveith the comings and goings of the ice ages. The continents themselves have moved slowly about the earth like great boats floating on syrup, sometimes colliding to produce new mountain ranges. They still move, so slowly that even the most sensitive instruments can hardly detect the movement. But geology is more patient; even half an inch a year means a movement of 80 miles in 10 million years. It is now believed that all the land masses on the earth once formed a single continent, given the name Pangaea. This continent first broke into two parts, Laurasia and Gondwanaland, and later broke up into the continental masses of today. A glance at a map shows how neatly the outline of South and Central America fits into the shape of Africa. The present shape of the continents can be explained by assuming that each of the continents was carried along on a huge plate iioating on the earth’s mantle. Where the edges of these plates met, they either collided head on (and mountains were formed) or they slid uneasily past each other in a jerky movement, producing earthquakes. HOMO SAPIENS At Swanscombe in England and Steinheim in Germany have been found fossils which suggest that our own species may be up to 250,000years old; their skulls look very like our own. Hand-axes of the period (below) produced in Europe, Africa and western Asia are more sophisticated and ehicient than earlier tools, with flatter surfaces and straighter edges