A moraine-dammed lake occurs when the terminal moraine has prevented some meltwater from leaving the valley. Its most common shape is that of a long ribbon (ribbon lake). Example of moraine dammed lakes include:
In the 19th century the Argentine explorer Francisco Perito Moreno suggested that many Patagonian lakes draining to the Pacific were in fact part of the Atlantic basin but had been moraine dammed during the quaternary glaciations changing their outlets to the west. He argued that as originally belonging to the Atlantic basin these lakes should be awarded to Argentina. Most of the lakes situated in the Himalaya of Nepal and Bhutan are also of the moraine dammed type. They may burst at any time. That is why the areas below such lakes have high risk of flooding.