Kerlingarfjöll is a range of rainbow-colored mountains built from rhyolite, tinted in many places with sulfur and iron compounds. The mix of colors is exceptionally intense, allowing you to admire a palette ranging from black through grays, greens, yellows, reds, and various shades of browns to white silica deposits and patches of snow in some places. Kerlingarfjöll is part of a large volcanic system dating back 10,000 years. The area is characterized by intense geothermal activity, primarily manifested through dense columns of steam, smoking slopes, bubbling mud pots, and boiling muddy water.