Layers

Iceland is a young country geologically speaking, only about 20-25 million years old (the Earth is 4600 million years old). The buildup of the Icelandic plateau has all taken place during the lattr part of the Cenozoic era. The Icelandic plateau is almost entirely made up of basaltic lava flows with sediments in between. The lava flows have formed during volcanic eruptions, which is not surprising considering that Iceland like Hawaii is a so-called hot spot where eruptions are more common than elsewhere. The geological formations of Iceland are divided roughly into four different categories. Oldest is the so-called blue rock formation from the late Tertiary that comprises the farthest of the Westfjords and parts of the Eastfjords. Then comes the gray rock formation that was formed during the first part of the Ice Age and thirdly there is the hyaloclastite formation formed during the later stages of the last Ice Age. Those three formations, form, roughly speaking, the bedrock of the country on which the fourth and youngest formation is superimposed. This young formation is mainly made from loose sediments, such as gravel, soil, volcanic ash and recent lava fields.

The Tertiary lava formations have mainly been formed in very liquid lava flow eruptions that formed around ancient central volcanoes.

The later part of Cenozoic is called Quaternary. This epoch is divided into the Ice Age (Pleistocene) and recent times. From the beginning of the Ice Age there were around 3,100,000 years until about 10,000 years ago when the Ice Age stopped. The Ice Age is divided into glacial and interglacial. During the glacial, Iceland was covered by ice shields, but most probably with certain nunataks and a few small areas were ice–free. The hyalocastite mountains formed in sub-glacial eruptions and in many places there are thick sediments of glacial till from the last Ice Age.

Around 18,000 years ago the climate started warming after the enormous freeze of the last glacial, and the ice shield started melting. Land rose above sea level and the sea subsided. Around 10,000 years ago the Ice Age was finished and in the present the current interglacial is still going strong.