Pressure ridge (lava)

In volcanology, a pressure ridge or a tumulus (plural: tumuli), and rarely referred to as a schollendome, is sometimes created in an active lava flow.

[1] Formation occurs when the outer edges and surfaces of the lava flow begin to harden.

[1][2] Inflation also takes place and is a process where the plastic layer of lava underneath expands as it cools and small crystals form.

[1] The result is a raised mound of hardened lava rock, usually a relatively narrow but long ridge.

[1] Along the edges of a pressure ridge, if the tension crack is large enough it will create a liftup cave.