Very Cool Little Hills
(image via: Tahoe Is Walking On)
Geologists know them as hydrolaccoliths but “Pingo”, an Inuit word meaning “small hill”, goes down a whole lot easier. Pingos look like small mountains or volcanoes but the processes that lead to their creation couldn’t be more different. The world’s tallest pingo is Kadleroshilik Pingo situated about 40 kilometers (25 miles) southeast of Prudhoe Bay, Alaska. This hydrogeological formation rises to an elevation of 54 meters (178 ft) above the surrounding plain that was once a shallow prehistoric lake.
(images via: Panoramio/eugenepotapov)
Pingos are only found in cold climates, specifically arctic and subarctic regions of the northern hemisphere where the ground is subject to permafrost. They’re formed when successive freeze-thaw cycles produce an expanding ice core which, if fed by an underground water source, can grow to astonishing proportions. In Russia pingos are known as “bulgunniakh”, a word taken from the Sakha language of Siberia’s native Yakut tribes. The curious ringed pingo above is located in Nizhnekolymskiy ulus, Sakha, Russia.
The process of pingo formation is related to frost heaving, or what happened to glass bottles of milk and cream left on the doorstep by the milkman in sub-freezing temperatures… back in the days when there were milkmen who used to deliver glass bottles of milk and cream to homes. Water (and watery liquids like milk and cream) expands when it freezes, and one might wake up to find a semi-frozen bottle of milk on their doorstep with the cardboard cap sitting atop a 2-3 inch stack of frozen milk. In warmer eras, pingos will decay and may have unfrozen “crater lakes” at the summits.