Tumulus
Photograph by Janet Babb, June, 1990. Used with permission.
A tumulus is a "doming or small mound on the crust of a lava flow, caused by pressure due to the difference in rate of flow between cooler crust and more fluid lava below. Unlike a lava blister ... it is a solid structure" (Bates and Jackson, 1980, p. 669). The tumulus shown in this photo is on the south flank of Kilauea Volcano.
