Definição: A depression caused by erosion by water or ice. Low-lying land bordered by higher ground; especially elongate, relatively large gently sloping depressions of the Earth's surface, commonly situated between two mountains or between ranges of hills or mountains, and often containing a stream with an outlet.
Definição: A lake or estuary that is formed at the mouth of a river where flow is blocked by a bar of sediments. It can be maritime (the bar being created by the current of a sea) or fluvial (the bar being created by the flow of a bigger river at the confluence).
