Earth's surface is changing all the time. Some changes are very slow. Some changes happen very quickly.

One kind of change is caused by weathering. Weathering is the process by which large rocks are broken down into small pieces for many years. Weathering can happen in many ways. Rushing water and strong winds can weather rocks. Changing temperatures and some chemicals can also weather rocks. Usually, weathering takes a very long time to occur.

Erosion happens after weathering. It occurs when weathered rocks or soil are carried away to other places. Typically, wind, water, and glaciers cause erosion. Like weathering, erosion is often a slow process. For example, it took the Colorado River millions of years to make the Grand Canyon. This is water erosion. Wind erosion can blow away valuable soil and make deserts. A glacier is a huge mass of moving ice. It moves rocks and other things in its path wherever it goes.

地球表面不斷在改變，有些改變非常緩慢，有些卻非常快速。

其中一種變化由風化所造成，這是大塊岩石經年累月被分解成小顆粒的過程。風化的方式有很多種。急流和強風可以風化岩石，溫度的改變和某些化學物質也可能風化岩石。通常，風化作用的發生需要經過一段很長的時間。