A submerged forest is the in situ remains of trees (especially tree stumps) that lie submerged beneath a bay, sea, ocean, lake, or other body of water. These remains have usually been buried in mud, peat or sand for several thousand years before being uncovered by sea level change and erosion and have been preserved in the compacted sediment by the exclusion of oxygen. A forest can become submerged as the result of a lake or sea level rise that results in a lacustrine or marine transgression and in-place drowning of the forest. A submerged forest that lies beneath a lake can also be formed by the blockage of a river valley by either a landslide or manmade dam.