around 70,000 years ago and has an area of over 1,000 square kilometres.
While many crater lakes are picturesque, they can also be deadly. Gas discharges from Lake Nyos (Cameroon) suffocated 1,800 people in 1986, and crater lakes such as Mount Ruapehu's (New Zealand) often contribute to destructive lahars.
Certain bodies of water, although their formation is directly related to volcanic activity, are not usually referred to as crater lakes, including:
• Lakes created by volcanic dams due to lava flowing outside of the volcanic edifice/caldera (such as Garibaldi Lake in Canada, Fuji Five Lakes in Japan),
• Closed atoll lagoons (such as Clipperton lagoon), whose formation process also implies subsequent biogeomorphologic processes,
• Ponds encountered at the bottom of waterfalls occurring in volcanic canyons in a volcanic context but not within a volcanic edifice/caldera (such as Trou de Fer on Réunion Island).
Other kinds of crater lakes
Lakes can also fill impact craters, but these are not usually referred to as crater lakes except in a few isolated cases. Example of such impact crater lakes include Manicouagan in Canada, Lake Bosumtwi in Ghana and Siljan in Sweden.
More rarely they can also fill craters caused by artificial explosions, such as the radioactive Lake Chagan in Kazakhstan.
Other geological features that can be mistaken for a crater lake
Some geomorphological features, when filled with water, can sometimes be confused with crater lakes:
• Pingos (soil-covered ice mounts) whose summital part has collapsed,
• Sinkholes (karstic holes, also called cenotes), such as Otjikoto Lake in Namibia.
Some circular open-pit mines can also present a similar appearance, such as Big Hole in Kimberley, South Africa, a diamond mine (in akimberlite pipe) where water
