[by:www.51voa.com] [00:00.00]¸ü¶àÌýÁ¦Çë·ÃÎÊ51VOA.COM [00:00.16]This week, America celebrated the National Park Service's 100th birthday. [00:07.00]Yellowstone National Park became America's first national park in 1872. [00:16.88]The National Park Service was formed 44 years later in 1916. [00:24.08]Yellowstone, which is mostly in the state of Wyoming, [00:31.16]is considered an example of the success of the National Park System. [00:37.12]Humans have been present in Yellowstone for more than 11,000 years. [00:43.92]The first organized exploration of the area [00:48.24]which lies close to the continental divide of North America took place in 1870. [00:57.92]Those first organized explorers must have seen right away how special the land was. [01:06.00]Yellowstone contains beautiful mountains, deep canyons, lakes and rivers. [01:15.80]The name Yellowstone comes from the river running through the area. [01:22.72]At first known as Rock Yellow River, [01:26.80]it became known as the Yellowstone River. [01:30.80]Yellowstone is host to many different species of plants. [01:36.29]However, the park is most special because of what lies underneath it. [01:42.93]It sits on top of an ancient super volcano, known as The Yellowstone Caldera. [01:51.48]The caldera is 48 by 72 kilometers. [01:57.24]And it remains an active volcano. [02:00.88]It is believed that the last time the volcano exploded [02:05.36]or erupted was one half million years ago. [02:10.36]The area has had three major eruptions in the last three million years. [02:19.16]Experts say it may erupt again in another 1,000 to 10,000 years. [02:27.52]But each year, there are thousands of earthquakes at Yellowstone. [02:32.56]Most are too small to be felt by people visiting the park. [02:38.32]Yellowstone is filled with the beauty of many thermal or hot water springs. [02:45.80]Of all the geothermal places in the world, half are in Yellowstone. [02:52.60]In places of geothermal activity, [02:56.56]hot water and gasses are trapped under the earth's crust. [03:02.04]In places like Yellowstone, they rush to the surface [03:06.60]in the form of hot water and steam to form geysers. [03:12.48]There are more geysers and hot springs in Yellowstone than anywhere else on Earth. [03:22.28]The most famous geyser is Old Faithful. [03:26.04]It erupts about every hour or hour and a half. [03:32.16]The eruption can last from one and a half minutes up to 5 minutes. [03:40.76]The amount of hot water it expels in that time can be as much as 31,000 liters or more. [03:52.68]In addition to its beauty and wonder, Yellowstone is an animal sanctuary. [04:01.96]It is home to the largest group of wild animals in the lower 48 United States. [04:09.68]As you travel through the park, you can sometimes see them in their natural habitat [04:16.60]and hear their calls to mate and defend themselves. [04:21.04]Listen to this elk's bugle. [04:26.20];There is still a wild west in America and its name is Yellowstone. [04:33.60]I'm Dorothy Gundy.