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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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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.

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In today’s world, the ice sheets of Antarctica and Greenland. An ice sheet is a continuous mass of ice covering more than 50,000 km2. The ice sheet in Antarctica covers 14 million km2. It is 1.6 to 6.4 km thick and holds 30 million km2 of ice. The Greenland ice sheet covers about 1.7 million km2.

The Antarctic ice sheet is the largest block of ice on Earth. It covers more than 14 million square kilometers (5.4 million square miles) and contains about 30 million cubic kilometers (7.2 million cubic miles) of water.

The Antarctic ice sheet is about 2 kilometers (1.2 miles) thick. If it melted, sea level would rise by about 60 meters (200 feet).

The Greenland ice sheet is much smaller than the Antarctic Ice sheet, only about 1.7 million square kilometers (656,000 square miles). It is still the second-largest body of ice on the planet.

The Greenland ice sheet interacts much more dynamically with the ocean than the Antarctic ice sheet. The annual snow accumulation rate is more than double that of Antarctica. Glacial melt happens across about half of the Greenland ice sheet, whereas it is much more isolated on the far western part of Antarctica. Greenland's ice shelves break up much faster than those surrounding Antarctica.

Both the Antarctic and Greenland ice sheets have caused the land under them to sink. Eastern Antarctica is about 2.5 kilometers (1.6 miles) below sea level because of the colossal weight of the ice sheet above it.

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A desert is defined by the amount of precipitation (rain, snow, mist and fog) in an area. A region that receives very little precipitation is classified as a desert. There are many types of deserts, including subtropical, coastal and polar deserts. What they all have in common is a barren, windswept landscape, which makes it difficult for plants and animals alike to gain a foothold on land. This all certainly applies to Antarctica.

The average yearly rainfall at the South Pole over the past 30 years was a tiny 10 mm (0.4 in). Most of the continent is covered by ice fields carved by the wind, and craggy mountains covered in glaciers. While Antarctica is home to wonderful forests of low-lying mosses and lichens, there are only two flowering plants that can survive the harsh conditions. And most of the animals we encounter – penguins, seals, whales and seabirds – rely on seafood for sustenance.

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• The age of the oldest glacier ice in Antarctica may approach 1,000,000 years old
• The age of the oldest glacier ice in Greenland is more than 100,000 years old
• The age of the oldest Alaskan glacier ice ever recovered (from a basin between Mt. Bona and Mt. Churchill) is about 30,000 years old.

Glacier flow moves newly formed ice through the entire length of a typical Alaskan valley glacier in 100 years or less. Based on flow rates, it takes less than 400 years for ice to transit the entire 140 + mile length of Bering Glacier, Alaska’s largest and longest glacier.

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Almost 10 per cent of Earth’s total landmass is covered by ice. This includes glaciers, Ice caps and ice sheets. Glaciers cover 15 million km2. During the last ice age, 32 per cent of the total land area was covered by ice.

Most of the Earth’s ice that we see is to be found in large masses of “nearly” pure ice: ice-sheets and glaciers of various types, ice shelves and sea ice packs. It is quite easy to calculate the surface of the areas covered with ice: it has been calculated that this amounts to approximately 15 million km2, equal to one tenth of the surface of the Earth’s emersed land. It is more difficult, on the contrary, to calculate the volume of ice because the thickness of the entire covered area must be known: using special techniques it is possible to measure the ice thickness in various points of a glacier and therefore to estimate the volume. For example the average thickness of the Antarctic sheet is 2,100 m, with peaks of 4,800 m in Land of Wilkes, in the Eastern sector: with a surface of little less than 13,600,000 km2, the total volume of the Antarctic ice is 30 million km3.

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The Antarctic ice cap contains about 91% of all the ice in the world and about 86% of all freshwater that occurs in the form of ice. But despite all this freshwater, Antarctica is considered one of the most arid places on Earth.

Antarctica is the highest, coldest, driest, and windiest of the world’s continents. It is also “tallest” in terms of average height above sea level. Nearly 99% of this land mass is covered with an ice cap with an average altitude of around 2 200 metres above sea level. The area of this vast continent – some 14 million square kilometres – doubles in the winter, when sea ice can stretch as much as 1000 km outwards from the coastline.

Most of the continent of Antarctica lies south of 70°S, although the Antarctic Peninsula stretches northward as far as 60°S. The continent is surrounded by the Southern Ocean, a circumpolar sea that isolates Antarctica from the other continents.

Most of Antarctica is covered with ice, but in many places mountain peaks (nunataks) stick up out of the ice. The Vinson Massif in West Antarctica, with an elevation of 5 140 m, is the highest peak in Antarctica. In addition to the nunataks, there are large ice-free regions called oases where the ice has retreated and where melting outstrips accumulation of new snow. Other areas, known as dry valleys, are free of ice because essentially no precipitation falls there.

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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.

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