Last Glacial Maximum

The Last Glacial Maximum (LGM), also called the Last Glacial Coldest Period, was the most recent time when huge ice sheets covered large parts of the world. This happened between 26,000 and 20,000 years ago, during the Last Glacial Period. Enormous sheets of ice stretched across much of Northern North America, Northern Europe, and Asia.

Because of these thick ice sheets, Earth's climate changed dramatically. Many areas became much colder and drier, causing deserts to grow larger. The weight of the ice also pushed down on the land, and when the ice melted later, sea levels rose sharply.

Scientists study this time using special methods like terrestrial cosmogenic nuclides and radiocarbon dating. They have found that ice sheets in the southern hemisphere began growing about 33,000 years ago, reaching their biggest size between 26,500 and 20,000 years ago. Later, as the ice melted, sea levels rose quickly, especially when parts of the West Antarctica ice sheet began to break up. This major change in our planet's ice and climate shaped the world we live in today.

Glacial climate

The Last Glacial Maximum was a very cold time about 21,000 years ago when the world's average temperature was about 6 °C colder than today. During this period, large areas of Earth were covered in ice, and sea levels were much lower—about 125 meters below what they are now.

Many parts of the world were much drier and cooler. Deserts grew larger, and rainforests shrank. Some places, like parts of the western United States, actually had more rain and large lakes formed. In Australia, sand dunes covered much of the land. Overall, the climate was very different from what we experience today.

World impact

During the Last Glacial Maximum, much of the world was cold and dry. Massive ice sheets locked away water, lowering sea levels and exposing continental shelves. This created extensive coastal plains and joined land masses together. The ice sheets also changed atmospheric circulation, causing cooler temperatures and more clouds, which reflected sunlight and amplified global cooling.

In Africa and the Middle East, many smaller mountain glaciers formed, and deserts like the Sahara expanded. In Asia, ice sheets covered modern Tibet and other regions, while sea levels dropped, connecting islands to continents. Europe was largely covered by ice, with the southern boundary passing through Germany and Poland. North America saw large ice sheets covering Canada and extending into the United States. South America experienced glacier advances in the southern Andes. These changes had a major impact on global climate and landscapes.

Late Glacial Period

The Late Glacial Period came after the Last Glacial Maximum and before the Holocene, which began around 11,700 years ago. This period marked changes in Earth's climate as ice sheets began to retreat, leading to warmer conditions that eventually resulted in the modern climate we experience today.