The U-shaped valleys that house New York's Finger Lakes were sculpted out by massive sheets of ice. Glaciers withdrew north around 10,000 years ago, leaving deposits of gravel that blocked streams and created depressions to form lakes. The largest of these is Lake Erie, which stretches from Cleveland to Niagara Falls.
The Great Lakes are a group of five large bodies of water in North America: Lake Huron, Lake Superior, Lake Michigan, Lake Ontario, and Canal de l'Ouest (now part of Lake Saint Clair). They are the largest freshwater lakes in total area in Canada and United States. With an average depth of 50 feet (15 m), they are also among the deepest lakes in the world. The only other larger lakes in the Americas are Argentina's Lake Titicaca and Chile's San Antonio Reservoir.
The largest lake by volume is Lake Superior, which takes up almost half of Wisconsin. It contains 20% of the world's fresh water reserves not tied up in ice. The next three largest are Huron, Michigan, and Ontario, in order of size.
Lake Erie has 110 miles (180 km) of shoreline; it is the second most populous lake after Lake Ontario. Port Dover on its southern end is the oldest settlement in Ontario; it was first settled in 1792.
During the last Ice Age, New York was blanketed by a mile-thick sheet of ice. Valleys, lakes, rivers, and even rounded mountain ranges were formed by the power of this ice. This canal filled with water as the glaciers collided, forming the Hudson River. The ocean washed over the land until the ice melted away.
Today's landscape of New York City was shaped by other forces than ice: wind and water. When the Earth changes temperature, rocks at the surface melt first, then water, then sand, then clay. As the rocks cool they contract, causing valleys to form. Over time, these valleys are filled with water or covered with rock. That is why there are so many mountains in New York State!
Mountain building continues today through the process of erosion. Water wears away rock, which leaves more hard surfaces for water to wash away. Erosion has removed almost all of the soil along the riverbank, leaving only hardpan (solid rock).
The Hudson River was once completely different from what it is now. During the last Ice Age, when much of New York was frozen under a mile of ice, water flowed much farther into its present-day course. At that time, sea levels were about 140 feet lower than today, so instead of flowing into Long Island Sound, the Hudson River entered a large bay that extended far beyond present-day New York City.
Many lakes, particularly in the Northern Hemisphere, were produced by glaciers that covered significant amounts of land during the most recent ice age, around 18,000 years ago. These materials were occasionally used to build dams, which confined water and resulted in the formation of new lakes. Many glacial lakes dot the landscapes of North America and Europe.
Lakes can also be formed by volcanic activity. The largest lake created by a volcano is Lake Tahoe, which forms where the Reno-Lake Tahoe Basin lies within Nevada and California. The first humans to visit Lake Tahoe were Spanish explorers in 1772. They called it El Desierto (the desert) because there was no vegetation around its edge.
Today, many people come to Lake Tahoe for recreation including hiking, biking, fishing, cross-country skiing, and more. It is estimated that about 40 million people will visit Lake Tahoe this year.
Lakes can also form when a glacier melts at the end of an ice age. Water from the melting glacier flows into the surrounding terrain. If the terrain is flat enough, it may accumulate into a lake. Lakes can also form when large bodies of water such as oceans or large reservoirs fill up and then drain away. This happens with oceanic plates moving under them, forming trenches. Over time, the water in these trenches collects and becomes deep enough for other things to live in. This process creates many beautiful islands scattered across the oceanic floor.
During the previous ice age, glaciers retreated, forming the Great Lakes and lakes in Minnesota. Glaciers alternately withdrew and surged across the landscape between 15,000 and 9,000 years ago, cutting huge holes and leaving behind ice pieces. As the glaciers melted, they left behind large bodies of water.
The last glacier to cover most of Minnesota receded around 10,500 years ago, leaving behind the present-day state border with Wisconsin. Since then, wind and rain have shaped the remaining glaciers, which contain a large amount of water vapor that comes out when they melt in summer. This causes periods of drought and floodage throughout the year. Lake Minnewawa, for example, is expected to disappear by 2025 if it doesn't receive more rainfall. The average annual precipitation in Minnesota is 40 inches, so this makes Lake Minnewawa important for water supply.
Most lakes in Minnesota began as glacial valleys. The shape of a valley is determined by the location of the mountain range that forms it. Where there is no mountain range, such as near the coast, the valley will be deeper and more elongated. Where there is a steep mountain range, such as in the center of the state, the valley will be narrower and flatter on the bottom.
Lakes also change shape over time.
The Great Lakes began to emerge some 14,000 years ago, towards the conclusion of the last glacial epoch, when retreating ice sheets revealed the basins they had cut into the terrain, which subsequently filled with meltwater. The opening of these new waterways allowed for the development of wetlands that provided habitat for a number of species including many forms of fish.
During the most recent ice age, sea levels were about 120 feet lower than today, and the Atlantic Ocean met the Pacific Ocean where now stands California. All of North America was covered in one big ice sheet, from Canada down to South America. When the ice melted, it left behind rock depressions called glacial valleys that are still visible in some places today. As the water drained away, any rocks exposed by the erosion of the valley walls formed islets called "boulder beaches." Over time, more soil developed on these beech trees, creating fertile areas suitable for human settlement.
The appearance of modern day Lake Michigan was influenced by two major glaciers. One was a large ice sheet that at its closest point reached as far south as Long Island before melting back north of where it started. The other was a smaller glacier that flowed out of Canada and stopped just east of present-day Chicago. As this glacier melted, it left behind Helvetia Desert, a flat area of land nearly 50 miles long by 10 miles wide.
As they traveled slowly, the massive slabs of ice dug out large trenches and cleaned the soil. When the glaciers melted, the depressions were filled with water, generating lakes. As they melted, glaciers formed vast valleys and deposited massive amounts of dirt, stones, and boulders. The collision of many glacial blocks created extremely rugged terrain with steep cliffs and tall peaks. These features can be seen on Earth today in places like Glacier National Park in Montana.
The United States has more than 12 million acres of protected land, including national parks, forests, and wildlife refuges. This means that there is a good chance that you will encounter some form of nature protection. However, this does not mean that you cannot see other forms of nature's work as well. For example, scientists have recently discovered how glaciers affect climate change by analyzing the contents of their cells. They have found that glaciers contain huge amounts of salt which melt when they reach the surface of the ground. This salt then flows into nearby rivers or lakes, where it helps to fertilize them. The water becomes more alkaline as a result, which affects how much acidity it can hold and may even help protect against other types of pollution.
Other countries also have large areas of protected land, but they do not have as many opportunities to see the impact of glaciation up close.