East of Reykjavik there is a mountain called Hengill. Hengill is formed from Palagomite tuff and its highest point is about 800 meters above sea level. Hengill is a central volcano and has a huge magma chamber below it.
As lava cools, it contracts. This is because hot things usually take up more space than cool things. For example, think about hot steam. When you open the lid of a boiling pot or teapot, that hot steam wants to escape and release into the air.
When thick basaltic lavas cool, they tend to form hexagonal cracks, called columnar joints. Among the world’s most famous examples of these “columnar basalts” are the Giant’s Causeway in Ireland and the Devil’s Postpile in California.
No exposures of such scales exist in Hawaiʻi, but the columnar joint in the Mauna Loa flow exposed at Boiling Pots, although small, provides an excellent opportunity to observe the results of lava cooling .
Iceland’s south coast has a lot to offer. We start by driving south on Highway 1. We explain to you the geology of Iceland and show you the many wonderful and interesting places that have appeared in Iceland both past and present in.
