1 . Mountain
A mountain is a landform that rises high above its surroundings. Taller than a hill, it usually has steep slopes and a rounded or sharp peak. Mountains are rarely found alone.
Some mountains were formed by the activity of volcanoes. Scientists believe that most volcanic mountains are made up of rock that melted deep within earth. The rock rose through Earth’s surface, or crust. It then flowed onto the surface in the form of lava.
Other mountains were formed by movements within Earth’s crust. The theory called plate tectonics explains this type of mountain building. Earth’s crust is divided into huge pieces called plates, which move very slowly. The continents sit on top of the plates and move with them. At times the plates strike against each other, forcing the rock upward. The Himalayas of Asia are an example of this type of mountain chain.
Mountain ranges are natural barriers to travel. Roads are difficult to build across them. Railroads need expensive tunnels to cross even low mountains.
Life is hard in mountain lands. The high places of the world are cold and have little soil, making farming difficult.
| A．Groups of mountains are called ranges. |
| B．However, many mountain areas are vacation spots. |
| C．The lava, along with volcanic dust, built up to form mountains. |
| D．These colder climates strongly affect the ecosystems of mountains. |
| E．Thus the continental crust is normally much thicker under mountains. |
| F．Therefore mountain ranges tend to divide the people on either side of them. |
| G．They were formed when a plate carrying India struck against the Asian plate. |
