Ice Age. The ages of the Earth

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This image shows karst formations inside a cave. Water seeps into the porous rock and erodes it. Some of these formations are the result of the advances and setbacks of the sea caused by the glacial ages.

In 1840 the Swiss Louis Agassiz, studying the rocks of the Alps, concluded that in the past there were glacial ages. Then he was not taken seriously, but today nobody doubts that he was right. Throughout the planet there is geological evidence of past glaciations: U-shaped valleys eroded by ancient glaciers, fjords, drumlins, karst caves, cenotes ...

Since the Proterozoic, more than 2,000 million years ago, warm periods alternate with long ice ages. Over millions of years, the Earth cools and its ice expands. It is believed that, at least twice, the planet's surface was completely frozen. It is what is called Snowball Earth.

Quaternary glaciations are the best known. From the oldest to the most recent, they are: Günz, Mindel, Riss and Würm. The last glaciation ended 10,000 years ago. Since then, we live an interglacial period called Holocene.

Glaciations are caused by several causes. The movements of the continents, when separated and united by continental drift, also separate the oceans and modify their currents. Also the variations in the air currents and in the axis of terrestrial rotation (Milankovitch cycle).