When Does a Hill Become a Mountain?
There is no exact rule that indicates when a hill becomes a mountain. But scientists who study the surfaces of the Earth usually agree that when a hill is 2,000 feet higher than the land around it, it can be called a mountain. The word, “mountain” means different things to different people.
People living in a nearly level plains area might call even a small hill a mountain. But those living in an area similar to Colorado would not call a region mountainous unless it was very high and rugged. Mountains cover a fifth of the Earth’s land area.
According to the U.S. Geological Survey, there is no official difference between hills and mountains. The United Kingdom and the United States used to define hills as summits less than 1,000 feet. However, both countries abandoned the distinction in the mid-twentieth century.
Sometimes, you’ll find a hill made by people. This is called a mound. In the Midwest region of North America, a network of Native Americans known as the Hopewell created huge mounds. In fact, the Hopewell people are often called Mound Builders. The most well-known mounds are in Hopewell Culture National Historical Park, in the U.S. state of Ohio.
The Hopewell people built mounds in the shape of spirals and domes. These mounds are about 9 meters (30 feet) tall and sometimes as wide as 305 meters (1,000 feet).
Archaeologists are unsure what the mounds were used for. Some may have been burial mounds for important people, or they may have been used as astronomical observatories.
Natural hills are formed all the time, by different types of geologic activity. One of these activities is faulting, which happens because the rocks underneath the Earth’s surface are constantly moving and changing the landscape. Hills formed by faulting can eventually become mountains. The Himalayas in Asia, the tallest mountain range in the world, were once tiny hills. The Himalayas continue to grow because of faulting activity beneath the Earth’s surface.
Hills are also formed because of erosion, which happens when bits of rock, soil, and sediment get washed away and placed in a pile somewhere else.
Hills can be destroyed by erosion, as material is worn away by wind and water. Hills can also be created by erosion, as material from other areas is deposited near the hill, causing it to grow. A mountain may become a hill if it is worn down by erosion.
Parts of the U.S. state of Indiana are almost entirely flat. However, other parts of the state have a ton of hills. Geologists and geographers have studied the lack of hills in northern Indiana.
They discovered that during the Ice Age, glaciers covered the area, mowing down the landscape as they advanced like steamrollers. The glaciers started to melt once they reached the middle of the state. Running water from the melting glaciers helped form the hilly, rugged landscape of southern Indiana.
There are a handful of different types of hills. A drumlin is a long hill formed by the movement of glaciers. A butte is a hill that usually stands alone in a flat area. It has steep sides and a flat top. The rest of the hill was eroded away. A tor is a rock formation on top of a hill.
Sometimes, especially in the United Kingdom, a tor also refers to the hill itself. A puy is a cone-shaped, volcanic hill. A pingo is a mound of ice covered with earth. These are found in the Arctic and Antarctica.
People have used hills for homes and urban areas for thousands of years. Many people have built their homes and villages on hills to avoid floods.
The higher elevation also allows people to defend themselves. Ancient Rome, for example, was built on the city’s seven hills so Romans could see their invaders coming from far away.