What force can change the shape of land?

Answer 1

When we consider changes in the shape of land, there are a number of things that can cause it. Plate tectonics, the shifting of the large "pieces" or tectonic plates that cover the surface of the earth, is a major cause of massive changes in the shape of land. The process is slow, but it moves whole continents around. Abrupt changes as stress between plates is relieved results in earthquakes. Also recall that a tsunami, a tidal wave, can be generated by earthquakes, and the massive movement of water can quickly change the shape of areas of land where it comes ashore. There are other forces that can change the shape of land, too.

Volcanic action can cause changes in the shape of land. The big island of Hawaii is increasing in area because of vulcanism. Volcanic action can be something that happens over weeks, months, years or decades. It can also happen in hours as was demonstrated by Krakatoa and other massive volcanic blasts.

Weathering by wind and water erode the land and change its shape. Uplift as a result of tectonic action builds whole chains of mountains, and weathering wears them down to small hills, all over many thousands or millions of years. A big river may move countless tons of material down its length to deposit it near its mouth.

Glaciers made of ice carve valleys out of the Earth's surface and have contributed to the creation of some of the most spectacular scenery on our planet. Also the weight of the ice sheets was large enough to depress the surface of the Earth (making the lithosphere sink further into the asthenosphere on which it floats). Once the ice sheets covering the Earth's surface melted (particularly in the northern hemisphere) the surface had to readjust and has started to rebound. This means that in places like the UK, Scotland and Northern England is actually rising and Southern England is sinking! This process is known technically as post glacial isostatic readjustment.

Once in a while a big rock from space will slam into the earth and change the shape of the land. The larger the rock, the more it can do to alter the terrain. Man can also change the shape of land. We dig big holes in the ground to recover minerals, and these holes can be seen from space. We also move material into the ocean to extend land or make islands. The new airport in Hong Kong is situated on land "created" by adding material to small existing islands, just to cite a single example.

Answer 2

Wind and water erosion.