Police departments and private detectives are not the only ones who use hidden clues to uncover events long passed. Massive amounts of natural history information are waiting to be uncovered in the landscapes around us. Using fairly simple clues, you can determine for how long areas in New Hampshire have been forested, when farming stopped, when and where blowdown events occurred, and even where fires scorched hillsides decades ago.
But you can take this even farther. In southwest Greenland, we’re particularly interested in how our study lakes were formed. We want to be able to look at a lake, and imagine the receding Laurentide Ice carving away cirques, or giant ice blocks melting in the moraine, leaving giant holes. We can do this, and it isn’t that difficult.
There are four main types of lakes (and many combinations thereof) we see around Kangerlussuaq, each with its own epic story of formation.
Cryogenic lakes are shallow dishes of water caught on top of permafrost blocks and ice-wedges. Water is held on the ground surface because the underground ice keeps it from flowing away. These lakes are extremely shallow, and usually have large cracks in the ground nearby, caused by expanding and contracting permafrost.
Cryogenic lakes near the Greenlandic Ice Sheet, with part of the Russel Glacier in the background.
Fault lakes are exactly what they sound like: large fault valleys filled with water, often due to landslide activity at either or both ends. These lakes tend to be very narrow and very deep. In Greenland, these are some of the only lakes not formed by glacial or ice activity.
These small lakes near the Sandflugtdalen all occur in the same fault valley, and are therefore probably fault lakes.
Cirque lakes are generally the most dramatic lakes we see in Greenland. Cirque lakes are formed by moving glaciers that carve out large amphitheater-shaped valleys in the landscape. They are also usually the easiest to identify, as they are almost always surrounded by steep mountains on almost all sides, and have small lips or ledges holding the water back at the outlet.
Sea Tomato Lake (the largest in this photo) is in a small cirque, and has a small moraine lip holding water back at its outlet. The bay to the upper left contains a kettle.
Kettle lakes are by far the most numerous lakes in Greenland. They are usually small, and form when a receding glacier leaves a block of ice to melt in the sediment, often over hundreds of years. These lakes often appear to occur randomly- on plains or in areas with no obvious valleys or depressions. A neat feature of kettles is that they hold the general shape of the ice block that formed them, so each one is very unique.
This lake, also near the Sandflugtdalen, is a typical kettle.