Effects of the last glacial period

The climate has changed many times on Earth. There have been several periods when it has been much colder than it is now. During these ice ages, ice has spread over large areas of land, forming ice sheets. Colder, glacial, periods of an ice age are separated by relatively warmer interglacial periods. We are currently in an interglacial period of the Quaternary Ice Age.

The most recent glacial period of this ice age lasted from about 115,000 to 11,700 years ago. How did this last glacial period affect Earth? In general, glacial periods cause enormous changes to the Earth’s surface. Over time, ice sheets grow and shrink. This movement picks up rocks and soil, eroding hills and mountains, and shaping the landscape.

The sheer weight of the ice can even cause the Earth’s crust to sink! However, once the ice sheets are gone, the ground begins rising again. This process is called post-glacial rebound. Post-glacial rebound has caused significant changes to coastlines and landscapes over the last several thousand years. Lake Mälaren in Sweden, for example, was formerly a part of the Baltic Sea.

But, by around the 12th century, uplift had turned it into a freshwater lake. Post-glacial rebound is still ongoing in many places, especially in Northern Europe, Siberia, Canada, and the Great Lakes region of North America. Studies suggest that in many places, rebound will continue for about another 10,000 years. Another effect of the last glacial period was the disappearance of many large animals. Woolly mammoths, sabre-tooth cats, giant armadillos called glyptodons… These large animals were known as pleistocene megafauna.

Then, beginning as early as 130,000 years ago, a major global extinction event of many hundreds of species of megafauna occurred. The reasons for this are not fully understood, but scientists have a few theories. During the most recent glacial period, much of the water on Earth's surface was trapped in thick ice sheets, so conditions were very dry. As the ice sheets expanded, large areas of land became totally uninhabitable. So animals had to compete for living space — and probably food, too.

It’s possible that much of Earth’s megafauna could not adapt to these changes. But there is another theory. It involves Homo sapiens – humans. During the last glacial period, humans and megafauna coexisted in many parts of the world. Archaeologists have found remains of tools and weapons that could have been used to hunt large prey.

Scientists believe hunting may have contributed to the decline of some species. Homo sapiens were not the only human species at the beginning of the last glacial period 115,000 years ago. At that time, Homo erectus was still living in modern-day Indonesia. The Denisovans were in Asia. The Neanderthals, meanwhile, had lived in Europe for hundreds of thousands of years.

And yet, all except Homo sapiens were extinct by the end of the last glacial period. Homo sapiens were likely able to adapt due to their large, complex brains. Homo sapiens’ advanced survival skills allowed them to adapt to many different environments and climates. After the glacial period ended, there was more moisture in the air, less frozen soil, and better conditions overall for plant and animal life. These conditions likely led to the beginnings of agriculture, and eventually, to the foundations of the first civilizations.