Landforms
Mountains are landforms higher than 2,000 feet or about 600 meters above sea level.山是海拔2000英尺(约600米)以上的地貌。
Hills are like mountains, but not as tall.山就像山，但没有山高。
Mountains are formed by forces deep within the Earth and are made of many types of rocks.山是由地球深处的力量形成的，由许多种类的岩石构成。
Rivers are streams of water that usually begin at mountains and flow into the sea.河流是水的溪流，通常从山上开始流入大海。
Many early cities were built alongside rivers.许多早期的城市都建在河边。
Most of the world's water is in the oceans, which are large bodies of salt water.世界上大部分的水都在海洋里，海洋是大的咸水体。
The oceans are also an important source of oxygen.海洋也是氧气的重要来源。
Deserts are areas of land that receive little or no rainfall.沙漠区是很少或没有降雨的地区。
The amount of rainfall in some deserts is so low that only a few plants can survive.有些沙漠的降雨量很低，只有少数植物能生存。
A valley is a low, relatively flat area between hills or mountains, often with a river running through it.山谷是山丘或山脉之间地势较低、相对平坦的地区，通常有河流流经。
Some valleys are formed by flowing water, and others are formed by glaciers.有些山谷是由流水形成的，有些则是由冰川形成的。
many early civilizations development near rivers许多早期文明都是在河流附近发展起来的
