Cryptodepression

Prealpine lakes in Northern Italy by elevation (surface and deepest point elevation). Lake Maggiore, Lake Lugano, Lake Como and Lake Garda are cryptodepressions.

A cryptodepression is a lake which has its water surface above sea level and its deepest point below sea level.^[1] The term is derived from the Ancient Greek word κρύπτoς ('hidden') and depression.

Description

A cryptodepression is often due to creation of a rift valley or a glacial lake.^[2]

Lakes are often long and narrow. Further, the surrounding landscape and the shore of the lake can be very steep.^[3]

Examples

Simple calculation example:
Lago O'Higgins/San Martín
Surface elevation  250 m -
Maximal depth      836 m =
_________________________________
Cryptodepression  -586 m

• Glacial lakes and moraine-dammed lakes: major prealpine lakes in Italy have cryptodepressions created by erosion. In other parts of the Alps, Swiss, Bavarian and Austrian lakes, cryptodepressions are not found because the lakes have significantly higher elevations. In North America, the Finger Lakes in New York are another example.
• Rift valleys: the deepest known cryptodepression on Earth is in Lake Baikal (-1200 m).^[4]

References

Look up cryptodepression in Wiktionary, the free dictionary.