Lake

A lake is a large pool of water.

It sits in a dip in the land. Most lakes have fresh water. Some lakes have salt water instead.

Rivers can flow into a lake. Rivers can also flow out of a lake. This helps the water move around the Earth. Some lakes have no rivers at all.

Lakes can form in many ways. Some form in holes made by volcanoes. Others form when big ice sheets move.

Some lakes are made by people. People build these to hold water. They use this water for many things.

Lakes are not the same as the ocean. They stay on the land. They are a special part of our world.

A lake is a large body of water.

It sits in a basin, which is a dip in the land. Most lakes hold fresh water. Some lakes are salt lakes. These have salt levels higher than the sea.

Lakes form in many ways. Tectonic lakes form when the Earth's crust moves. Volcanic lakes form in craters left by volcanoes.

Glacial lakes are made by moving ice. These are the most common lakes in the world. Some lakes form from rivers. An oxbow lake is a curved lake made by a river.

Some lakes are made by people. We call these reservoirs. People build them to hold water. They use this water for power or drinking.

Lakes are part of the water cycle. This is the way water moves around Earth. Most lakes are on land. They are separate from the ocean. Some lakes even exist on Titan. Titan is a moon of Saturn.

A lake is a large body of water on the Earth's surface.

It sits inside a basin, which is a low area of land. Most lakes are filled with fresh water. Some are salt lakes with very high salt levels.

These lakes are part of the water cycle. This is the way water moves around our planet. Lakes cover about 2.5 million square kilometers of Earth. This is less than 2% of the world's surface.

Lakes can form in many different ways. Tectonic lakes happen when the Earth's crust moves or shifts.

Volcanic lakes form in craters left by volcanoes. Crater Lake in Oregon is a famous example.

Glacial lakes are made by moving ice sheets. These are the most common lakes in the world. Some lakes form from rivers, like crescent-shaped oxbow lakes.

Others form in underground caverns or from melting snow.

Scientists study lakes to learn about our world. In 1957, G. Evelyn Hutchinson wrote a famous book about them.

He helped classify the many types of lakes. One type is called an endorheic lake. This is a lake with no natural way for water to flow out.

These lakes only lose water through evaporation or underground seepage. This can make them very salty over time.

Lakes are found in many different places. Canada has at least 2 million lakes.

Finland has 168,000 lakes that are large. Most lakes are in the Northern Hemisphere. Some lakes are even found on other worlds.

Titan is a moon that orbits Saturn. It has lakes that look like the ones on Earth. On Mars, scientists found dry lake beds from long ago.

People also make their own lakes. We call these artificial lakes reservoirs.

Humans build them for many important jobs. They use them for hydroelectric power to make electricity. They also use them for farming or for drinking water. Some reservoirs are built just for fun or for beauty.

Even though they are useful, all lakes are temporary. They will eventually fill with dirt or spill out of their basins.

A lake is a relatively large, fixed body of water located on or near the Earth's surface.

These bodies of water are localized within a basin or a series of connected basins surrounded by dry land. While lakes are separate from the ocean, they may be linked to it via rivers. Lakes play a vital role in the water cycle, which is the continuous movement of water around our planet. Most lakes contain freshwater, accounting for nearly all the world's surface freshwater. However, some are salt lakes with salinity levels even higher than seawater.

In total, lakes cover approximately 2.5 x 10^6 km², which is less than 2% of the Earth's surface.

Defining the exact difference between a lake and a pond can be difficult. There are no official scientific criteria or international definitions used by all disciplines. Some limnologists, who study inland waters, view lakes as simply larger versions of ponds. They might distinguish them by wind-induced turbulence that mixes the water column or wave action on the shore. Because of this uncertainty, many researchers use size-based definitions. These can range from 2 hectares to 8 hectares for a minimum lake size. The ecologist Charles Elton once suggested a lake must be at least 40 hectares.

In some regions, like Newfoundland, almost every lake is called a pond. In other places, like Wisconsin, the names are often reversed.

Lakes form through many distinct geological processes. Tectonic lakes are created by the movement of the Earth's crust, such as faulting, tilting, or folding. Some of the largest lakes, like Lake Baikal, occupy rift valleys. Volcanic lakes occur when water fills depressions like craters or calderas. For example, Crater Lake in Oregon formed in a caldera after Mount Mazama subsided.

Glacial lakes are the most numerous type in the world. They are created by the direct action of glaciers and continental ice sheets. These include subglacial lakes or epishelf lakes, which are found in Antarctica.

Fluvial lakes are produced by running water. A common type is the oxbow lake, which has a crescent shape. These form when a meandering river cuts through its own bend, leaving a horseshoe-shaped body of water behind.

In 1957, G. Evelyn Hutchinson published a landmark monograph titled *A Treatise on Limnology*. This work provided a comprehensive classification of lake types based on their origin and characteristics. Hutchinson identified 11 major lake types, which are further divided into 76 subtypes. His work remains a fundamental reference for understanding how lakes are distributed and how they function. This scientific foundation helps us categorize the vast variety of water bodies found across the globe.

Water management and movement also define different lake categories. Most lakes have at least one natural outflow, such as a river, to maintain their water levels. However, some lakes are endorheic, meaning they have no natural outflow.

These lakes lose water only through evaporation or underground seepage. This process can lead to very high salt concentrations in the water. Humans also create artificial lakes, which are known as reservoirs.

These are constructed for many purposes, including hydroelectric power, agriculture, and domestic drinking water supplies.

Lakes are distributed widely across the planet, with many located in the Northern Hemisphere. Canada is home to an estimated 2 million lakes, including over 31,752 that are larger than 3 square kilometers. Finland also has a high density of lakes, with 168,000 lakes measuring 500 square meters or larger.

While large lakes hold most of the world's lake water, small ponds are much more abundant. One study estimated there are 304 million lakes and ponds on Earth, with 91% being 1 hectare or less. This is because lake volume increases much faster than surface area.

Interestingly, lakes are not unique to Earth. Extraterrestrial lakes exist on Titan, a moon of Saturn.

The shape of these lakes is very similar to those found on our planet. Additionally, scientists have found evidence that lakes once existed on the surface of Mars, though they are now dry lake beds. Despite their importance, all lakes are temporary over long geological periods. They will eventually fill with sediment or spill out of their basins, changing the landscape once again.