Australia's southern Tasmania coastline is made up of impressive mountain pillars that rise up to 300 meters above sea level. Geologists call these rocks dolerites because of their pronounced long hexagonal columns.
Dolerites form when molten rock from the Earth's interior instantly cools and solidifies, forming small crystals in the rock. At a suitable cooling rate, the rocks contract in volume, causing cracks to form. Fractures cool deeper rocks, leading to more fractures. The result is a large block of rock with long and symmetrical vertical cracks that form five to six adjacent columns. Their sizes can range from a few centimeters to more than a few meters in diameter.
Tasmania's impressive dolerite columns formed during the Jurassic period, approximately 185 million years ago. This happened during a major volcanic eruption that covered a third of the island of Tasmania. The columns are part of a continuous ridge over 4,000 km long, stretching from Australia to Tasmania and to Antarctica.
Column rocks of this type are quite common. There are hundreds of famous places around the world where these formations can be found. These include the Giant's Bridge in Ireland, the Devil's Tower in Wyoming, Los Organos in Spain and Fingal's Cave in Scotland.
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