Category ICE AGES

HAVE THERE BEEN MANY ICE AGES?

There have been at least five major ice ages in Earth’s history: the Huronian,  Cryogenian, Andean-Saharan, late Palaeozoic and Quaternary. The study of rocks dates the Huronian around 2.1 billion years ago. The Cryogenic, around 700 million   years ago may have seen Earth almost totally frozen, like a snowball. The Andean-Saharan Ice Age happened around 400 million years ago. The late Palaeozoic, around 360 million years ago, had extensive polar ice caps. The Quaternary Age began around

2.5 million years ago. At present, Earth is in an interglacial period it is between ice ages.

There have been five or six major ice ages in the history of Earth over the past 3 billion years. The Late Cenozoic Ice Age began 34 million years ago, its latest phase being the Quaternary glaciation, in progress since 2.58 million years ago.

Within ice ages, there exist periods of more severe glacial conditions and more temperate conditions, referred to as glacial periods and interglacial periods, respectively. The Earth is currently in such an interglacial period of the Quaternary glaciation, with the last glacial period of the Quaternary having ended approximately 11,700 years ago. The current interglacial is known as the Holocene epoch. Based on climate proxies, paleoclimatologists study the different climate states originating from glaciation.       

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WHAT BRINGS ABOUT THE END OF AN ICE AGE?

The rotation and revolution of Earth, the amount of solar radiation and the amount of carbon dioxide in the atmosphere are all factors that contribute to a warming up of Earth, which ends an ice age. Changes in ocean currents also have a major effect on temperatures on Earth.

Over thousands of years, the amount of sunshine reaching Earth changes by quite a lot, particularly in the northern latitudes, the area near and around the North Pole. When less sunlight reaches the northern latitudes, temperatures drop and more water freezes into ice, starting an ice age. When more sunlight reaches the northern latitudes, temperatures rise, ice sheets melt, and the ice age ends.

Credit: American Museum of Natural History

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WHAT IS AN ICE AGE?

A very long period, it could be millions of years, during which major parts of Earth are covered with ice because of a significant drop in temperature, is termed an ice age. Geologists say that the most recent was the Little Ice Age, which started in the 16th century in Europe and many regions across the world and reached its peak in 1850.

An ice age is a period in which the earth’s climate is colder than normal, with ice sheets capping the poles and glaciers dominating higher altitudes. Within an ice age, there are varying pulses of colder and warmer climatic conditions, known as ‘glacials’ and ‘interglacials’. Even within the interglacials, ice continues to cover at least one of the poles. In contrast, outside an ice age temperatures are higher and more stable, and there is far less ice all around. The earth has thus far made it through at least five significant ice ages.

One glance at our icy poles and frozen peaks makes it clear that our current epoch (the Holocene, c. 12,000-present day) actually represents an interglacial within the ice age that spans the Quaternary geological period, which started around 2,6 million years ago and encompasses both the Pleistocene (c. 2,6 million years ago – c. 12,000 years ago) and the Holocene epochs. This entire period is characterised by cycles of ups and downs in ice sheet volumes and temperatures which can sometimes change as much as 15°C within a couple of decades. This rapidly overturning climate can have huge knock-on effects all around the world, altering vegetation and the types of animals that can survive in certain areas, and it helped shape human evolution, too.

Credit: World History Encyclopedia

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