Flow Ledge

Ledges are often left along the edges of sinuous lava tube passages, and are usually somewhat rectangular in cross-section, joining walls and floor. Curbs, benches, and shelves are other names commonly applied to these features, which mark the edges of late-stage flows. This is emphasized in Photo #3 where a later flow with different coloration formed ledges. Ledges may also occur higher on walls and be undercut, leaving catwalk-like suspended ledges. These features are more common near entrances since cooling is more rapid in those areas. Flow lines are along the same continuum but much smaller in cross section, but there is no distinct measure used to differentiate them from ledges. Photo 4 has a nice mixture of these two types of features.

AUTHOR: Dave Bunnell