Brennisteinsfjöll, (“Sulphur mountains”) a mountain ridge in the Reykjanes range, whence much lava has flowed all the way into the sea at Herdísarvík. It poured down from high ground, forming rocky cascades. Formerly this lava was thought to have flowed before the settlement of Iceland, but riding–trails have since been found that continue under the lava, so some of it must be younger than that. In the late 19th century the Scot W.G. Spence Paterson, for a time teacher at the Möðruvellir school and later British consul at Hafnarfjörður, started sulphur–mining east of the mountains but this never paid. The popular route between Hafnarfjörður and Selvogur once went via Grinda­skörð and east of the mountains.