How lakes are formed | Geography terms

Summary

The video explains what lakes are, how they vary, and how natural and artificial lakes form.

Definition and water sources

A lake is a body of water surrounded by land, usually occupying a low-lying basin. Lakes may receive water from rivers and streams, rainfall, melting snow or ice, groundwater, and seepage.

Where lakes occur and how they vary

Lakes are found in mountains, deserts, plains, and coastal areas. They range from small ponds to very large lakes; the Caspian Sea is described as the world’s largest lake. Lakes also vary in depth and elevation:

• Lake Baikal in Russia is identified as the world’s deepest lake, at nearly two kilometres deep.
• Lake Titicaca, between Bolivia and Peru in the Andes, is an example of a high-altitude lake, at about 3,810 metres above sea level.

Freshwater and saltwater lakes

Most lakes are freshwater, though some are salty. The video notes that saltwater lakes are commonly found near coastal areas.

Open and closed lakes

• An open lake has water flowing out through a river or another outlet. Freshwater lakes are usually open.
• A closed lake loses water through evaporation. As the water evaporates, salts and other solid matter remain, so closed lakes often become saline.

How natural lakes form

Lakes occupy basins or depressions in the land. These can form through several processes:

1. River and stream erosion: Ongoing flow removes sediment and can create a depression.
2. Tectonic activity and landslides: Earthquakes or related activity can trigger landslides, leaving low-lying areas where water collects.
3. Volcanic activity: After a volcano becomes inactive, its crater may fill with rainwater or melted snow.
4. Glacial activity: Moving glaciers carve the landscape, creating basins that later fill with water.

Artificial lakes

People create lakes by excavating land or building dams across rivers. These lakes are called reservoirs and are used to store water for irrigation, drinking, and industry.

Speakers and sources featured

• Narrator/presenter: Amit Sengupta, the video’s channel presenter.
• Other speakers or sources: None identified in the subtitles.