The small Grensdalur volcanic system (also known as the Hveragerdi system) lies at the eastern end of the Reykjanes Peninsula, SE of the Hengill volcanic system and south of the Hrómundartindur volcanic system. Grensdalur is the oldest of the three volcanic systems in the Hengill area and was last active during the Pleistocene. The Hveragerdi geothermal area contains high- and low-temperature geothermal features that include fumaroles, hot springs and pools, mud pots, and geysers, and provide heat to the town of Hveragerdi.