The Rocky Mountains of North America are quite old. Even though they were very volcanic millions of years ago, only a couple was still active today. In Yellowstone National Park, however, there is a large area of land, which indicates recent volcanic activity. This area contains hot springs, geysers and mud springs. Hot springs, like geysers, are caused by underground water being heated by hot rocks down in the earth. This hot water is then forced to the surface. When the surface rock is soft or porous, then the hot water bubbles up like a spring.
When the surface rock is hard, then the hot water shoots up through any hole in the rock that it can find. These spurts of hot water are called geysers. Yellowstone also contains mud pots or mud springs. These happen when the hot water is turned to steam, and the steam carries mud and clay to the surface. Yellowstone Park is high up in the Rocky Mountains of Wyoming.
Very few white people went there until the 1860s. It is said that Indians avoided the area because they thought that evil spirits lived there. In 1869, three men from Montana decided to explore this remote area. They were very impressed with its natural wonders and talked about it to others. Two other exploring expeditions followed in the next two years.
These visitors were so enthusiastic about the beauty and majesty of Yellowstone that they asked that it be made a national park. At that time, there was no national park system in America. Nonetheless, in 1872, the American government agreed to set aside these lands as a public park. Why were the early visitors to Yellowstone so impressed?
First, the scenery is spectacular. The Yellowstone River has created its own Grand Canyon through years of eroding its rocky banks. It is the yellow colour of these canyon walls that gave Yellowstone its name. The area has many waterfalls, including the 308-foot high Lower Falls in the Yellowstone River. There are many beautiful lakes, and the largest is Yellowstone Lake.