Geology

Abstract

Iceland is a volcanic island on the Mid-Atlantic Ridge with about 30 active volcanic systems and eruptions every 3–5 years, fed by a volcanic mantle plume under the island resulting in a so-called hotspot . The oldest rocks are from the late Tertiary , but much of the surface is covered by rocks <3 million years old, with widespread Holocene lava and tephra deposits. Glaciers cover about 11 % of the country and many active volcanoes are located under ice. The volcanism provides the parent materials of Icelandic soils by tephra deposition and aeolian redistribution. These materials are primarily basaltic in composition, while andesite and rhyolite also occur. The use of dated tephra layers in the soil is an important tool in environmental and archeological sciences in Iceland. The Quaternary glacier has carved out deep valleys in the Tertiary rock formations, while more recent landscapes are often characterized by plains and with mountains associated with volcanic systems. Glacial rivers and glacial margins are major sources for the aeolian materials mantling Icelandic land surfaces. Volcanic centers active during the Tertiary are often prominent on the landscapes, carved out by the Quaternary glaciation. Iceland receives a large amount of precipitation leading to many streams and major rivers, which include spring-fed rivers, glacial rivers, and runoff-based rivers.