Volcanic caves of Victoria (Small Tubes)

Subcrustal caves

Small, shallow, subcrustal caves form near the surface of a lava flow by drainage of still-liquid lava from beneath a thin crust.

See also the Poster (PDF) on Sub-crustal Lava Caves (KG Grimes, 2002). Prepared for the IUS conference on Volcano-speleology, Iceland, September, 2002.

Selected photographs and diagrams

To view full size images, click on the displayed image.
Small is better!
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Maps of some small subcrustal chambers. These are the simplest forms we find.
A shallow tube, showing the thin roof. 3H-64, Mt Napier.
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The small chamber, with lava drips, of Turtle Cave, Byaduk.
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Part of the upper-level crawls above Fern Cave.
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Not all tubes drain at the end of the eruption!
A completly lava-filled tube is exposed by breakdown at the edge of a lava channel at Mt Eccles. IMG00018.jpg

A set of three stacked subcrustal caves

For more details see the descriptions and maps of two of the caves imaged below 3H-106 and 3H-108 at Byaduk. These two and H-74 form a stack of three caves in separate thin lava flows.
A set of slightly more complex subcrustal caves. These have multiple chambers, and they have formed as a set of three, each in its own separate lava flow.
View of the entrances (numbered) to the three separate levels of caves. The cliff is the wall of a collapse into a deeper major feeder tube.
Chamber in 3H-74. Note sags and bulges in ceiling.
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Small chamber in 3H-74, with pahoehoe lava floor and lava drips on ceiling.
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A typical small low chamber in a subcrustal cave. 3H-106.
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Evolution into small feeder tubes

Continuing flow through a subcrustal system enlarges the active parts and modifies them into large and more cylindrical shapes.
These can act as feeder tubes for the advancing flow-front.
See also the Mt Hamilton Lava Cave, which has even larger evolved tubes, with remnants of the original tubelets in its walls.

A small feeder tube at the start of 3H-53, Mt. Eccles
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Another small cylindrical tube
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