Lava Fall

Like flowing water, a lava stream flowing underground can form a falls if the terrain on which the tube forms is suddenly steeper. Such falls can range from a few feet to over 70 feet high, requiring rope to negotiate, as in the fourth and sixth photos. But typically they are small and climbable, as in photos 1,2, and 5.

Photo 3 is an interesting phenomenon, where a large drip stalagmite has formed at the base of a tall lava fall, a later, small-volume flow that cascaded over the lip and piled up beneath it. This is a very different mechanism than most drip stalagmites form.

Many of the erosive features associated with waterfalls also occur with lava falls, with the hot lava thermally eroding into bedrock and back cutting. As the lavafall retreats upstream, it leaves a high-ceiling chamber downstream of it. Larger falls often have lava lakes formed at the base, where turbulence creates a deeper basin or plunge pool. Plunge pools can be quite deep, especially if the falls were not back-cutting. Studies indicate that their depth can be as much as twice the pool width.

Turbulence also results in passage widening at the base of the falls, typically with breakdown of the undercut walls above the growing plunge pool.

AUTHOR: Dave Bunnell