What happened during the last Ice Age?

Earth’s most recent glacial period began about 110,000 years ago and ended about 12,500 years ago. The maximum extension of the ice sheets of the glaciation, a period called the Last Glacial Maximum (LGM for its acronym in English, Last Glacial Maximum ), happened about 20,000 years ago.

This was the last glaciation of the Pleistocene, a geological epoch that is part of the Quaternary period of Earth’s evolution. The Pleistocene began 2.59 million years ago and lasted until 10,000 BC. Although several glacial cycles occurred at this time, with the corresponding interglacial periods (the warmest periods between extreme cold climates), the last glaciation is the one that has been best studied.

The geographical distribution of ice sheets

Approximately 26 million square kilometers of Earth were covered by ice at the time of the LGM; there were sheets of ice that covered large areas and glaciers that descended from the mountain ranges. The caps of the Earth spread out and covered vast regions. Here we break down a bit of what the world looked like at the time.

Europe

Iceland and Greenland were completely covered in ice, as was the area south of Iceland to the British Isles. Northern Europe was covered in ice as far as Germany and Poland, and glaciers projected from the Alps, the mountain range that stretches from Italy to Slovenia.

America

In North America, Canada was covered by ice sheets, as were some areas of the northern United States that extended south to the Missouri and Ohio rivers. In the American southern cone, the glaciation extended over Patagonia and covered the entire Andes mountain range, the mountain range that extends from southern South America; the ice covered Chile and a large part of Argentina and reached as far as the eastern cordillera of Colombia.

Southern hemisphere

On the other side of the planet but also in the southern hemisphere, the ice also covered New Zealand and several regions of Africa. In Southeast Asia, glaciers projected from mountainous areas.

ice age names

The name of the glaciation has been assigned according to the region where it has been identified and studied. The last glaciation, the Ice Age, receives the name of the Würm glaciation in the area of ​​the European Alps; in the north of the old continent it is called the Weichsel glaciation. In the area of ​​Patagonia it is called Llanquihue, due to studies carried out on sedimentary sequences extracted from Lake Llanquihue, in Chile. Further north, in the Venezuelan Andes, its name is Mérida glaciation, and Lauricocha in Peru. In North America there is talk of the Wisconsin glaciation.

Climate and sea level during the glacial period

The ice sheets began to form after a prolonged period of cooling of the Earth and an increase in precipitation, usually in the form of snow. Regions that today are desert received heavy rainfall, while other arid areas spread. The cold landscape of the newly formed ice caps altered weather patterns and the dynamics and composition of air masses. The new weather patterns reinforced the characteristics of the initial climate that created them, plunging the various regions into an ice age.

The warmer regions of the Earth also experienced a profound change in their climatic conditions due to the glaciation; most of them became colder and drier. For example, the vegetation cover of the tropical rainforest in West Africa was reduced and, due to decreased rainfall, it was replaced by tropical grasslands. At the same time, as the climate became drier, most deserts expanded. The exceptions are the regions of the American Southwest, Afghanistan, and Iran, which have become wetter due to changing atmospheric circulation patterns.

As the glacial period progressed to culminate in the LGM, the level of the world’s seas decreased; this happened as water was stored in the ice sheets that covered the continents and the extent of the polar ice caps. The sea level dropped about 50 meters in 1000 years. This level remained relatively constant until the ice sheets began to melt towards the end of the glacial period.

Changes in flora and fauna during the glacial period

Changes in climate due to glaciation altered the conditions for the development of vegetation in all regions of the Earth. The forms of vegetation that developed during the ice age are similar to those found today; this is the case with many trees, mosses and flowering plants. It is also valid for many species of insects, birds, shelled molluscs, and mammals.

Many mammals became extinct during the ice age, but there is multiple evidence of their existence; This is the case with mammoths, mastodons, long-horned bison, saber-toothed tigers, and giant ground sloths. The disappearance of species was very important in the American continent. It is estimated that during the Ice Age 46 genera of mammals became extinct in South America; about 80% of those that existed up to that time. In North America, 73% of large mammals disappeared; 33 genres. Species extinction was not as important in Europe, Africa and Asia; in many cases their habitats were restricted, but the species survived.

The history of the human being began in the Pleistocene with the appearance of the genus Homo more than two million years ago. The glaciation had a great impact on its development. Its impact on the population of America is an example: the drop in sea level allowed the migration of communities that lived in Asia to North America. The landmasses emerged in the Bering Strait connecting the Chukchi Peninsula in Asiatic Russia with Alaska in North America.

Vestiges of the Ice Age

Although the last ice age ended some 12,500 years ago, the vestiges of this climatic episode can be observed in many regions of the planet. Increased precipitation in the North American Great Basin area created huge lakes in a currently dry area. Lake Bonneville was one of them, once stretching over most of what is now the state of Utah in the United States. The Great Salt Lake is the largest section of what was once Lake Bonneville, and the shores of the former lake can be seen in the mountains surrounding the capital city. The name of Utah’s capital, Salt Lake City, means “saline lake city.”

The enormous energy associated with the development and movement of the glaciers generated drastic modifications to the landscape, such as the formation of extensive and deep lakes. The great lakes of Andean Patagonia were formed by the development of glaciers during the ice ages. An example is Lake Llanquihue, in Chile, which has a maximum depth of more than 350 meters and a surface area of ​​860 km ² and gives its name to the Ice Age in this region. In Manitoba, Canada, the many small lakes that dot the landscape were formed as the ice sheet rose from the land. Over time, the depressions that formed filled with water, creating lacustrine environments.

There are many glaciers all over the planet that have their origin in the last ice age. Most of the Earth’s ice cover is found in Antarctica and Greenland, but there are also vast icy regions in northern Asia, Canada, and Alaska. Beautiful and impressive glaciers can be found in many regions such as Mount Kilimanjaro in Africa; The Perito Moreno glacier in Argentina is located in the Andean mountain range of South America, which is shown in the presentation of this article. Due to the retreat that is observed in many of them, the glaciers are currently a matter of debate. Its retreat is associated with a new change in the planet’s climate, something that has happened over and over again throughout Earth’s 4.6 billion-year history.

Sources

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• Kaufman AJ; Knoll AH; Narbonne GM Isotopes, ice ages, and terminal Proterozoic earth history . Proceedings of the National Academy of Sciences of the United States of America 94 (13): 6600-6605, 1997.
• Rabassa J.; Chalmers MC. Quaternary glaciations of the southern Andes . Quaternary Sciences Reviews 9:153-174, 1990.
• Lee Clayton, John W. Attig, David M. Mickelson, Mark D. Johnson, Kent M. Syverson Glaciation of Wisconsin . University of Wisconsin, 2006.