The Reykjanes Peninsula ( ) in southwest Iceland is the continuation of the mostly submarine Reykjanes Ridge, a part of the Mid-Atlantic Ridge, on land and reaching from Esja in the north and Hengill in the east to Reykjanestá in the west. Suðurnes (transl. Southern Peninsula) is an administrative unit covering part of Reykjanes Peninsula. A great deal of volcanic activity was occurring in the Reykjanes Peninsula in 2020 and into 2021, after nearly 800 years of inactivity. After the eruption of the Fagradalsfjall volcano on 19 March 2021, National Geographic's experts predicted that this "may mark the start of decades of volcanic activity". The eruption was small leading to a prediction that this volcano was unlikely to threaten "any population centers". Origin The two most important factors for the existence of Iceland, rifting in combination with the Iceland hotspot, were responsible for the existence of Reykjanesskagi. Reykjanes Peninsula originated in a so-called rift jump 6-7 million years ago. At this time, the Snæfellsnes-Skagi rift had drifted so far to the west and away from the presumed steady place hot spot, that activity shifted eastwards in direction of this mantle plume which is now thought to be situated under the big glacier shield of Vatnajökull. Outcropping rocks have ages from 3.2 million years to the present. Volcanism and glaciations The topography of Reykjanes Peninsula was formed by glaciers and volcanism, basaltic lava fields covering a good part of the peninsula, in between volcanoes of subglacial as well as subaerial origin, namely tuyas, hyaloclastic ridges (tindars), shield volcanoes and crater rows. Some volcanic systems are submarine, so that there is a pronounced continuation between the volcanism of Reykjanes Ridge, a part of the Mid-Atlantic Ridge, and the Reykjanes Peninsula. Reykjavík region Famous in the area of Reykjavík is the Grágrýti (, Gray Lava). These tertiary basalt lava layers cover much of the ground around and under Reykjavík, but their origin is unknown. It is thought that the small hills within the city, some of which were islands during periods of glaciation, could be small shield volcanoes from warm spells of the glaciations. But it is known that during the Plio-Pleistocene (from 3.2 – 1.8 million years BP) two central volcanoes were active in the Reykjavík region, Viðey volcano and Stardals volcano. Both volcanoes partially formed Esja and the smaller mountains near Reykjavík and the hills on the islands and small peninsulas