Travelling Australia
Lava Tubes - Vic
Lava tube at Mt Eccles
Lava tube at Mt Eccles, between Hamilton and Portland in Western Victoria.
The Volcanic Region in the Victorian Western District is characterised by a large number of easily seen extinct volcanoes dotted around the landscape but there are also less easily seen underground structures left over from the era of volcanic eruptions. One of the most interesting is lava tubes; these are long underground, smooth sided tubes, usually wide and big enough for people to walk through.

Lava tubes form when liquid lava ejected from a volcano vent flows in a stream through recently solidified lava. As the edges of this flow cool a continuous crust of lava forms on top of the flow then merges with the walls forming a tube of cooler, hardened lava enclosing a stream of flowing liquid lava insulated by the hard crust on top. Over a prolonged period of time a lava tunnel can carry molten lava many kilometres from the vent without significant cooling.

Sinkhole at Byaduk
Sinkhole formed where a lava tube has collapsed at Byaduk. The lava tube was in a flow from Mount Napier, near Hamilton in Western Victoria.
Lave Tubes - page 2
If the lava in the tube flows away after the eruption a hollow tube encased in rock and up to several metres wide is left; usually the lava ejected from the volcano has raised the ground level so the tube is now underground. The tube may be continuous and run for many kilometres, or solidified lava may remain in parts of the tube blocking it off completely. Sometimes the roof of the tube collapses allowing birds and animals to enter the exposed cave; on other occasions the roof is strong enough to retain the oval cross section of the original lava tube.
   Volcano Discovery Centre, Penshurst.