The Undara Lava Tubes are the remnants of basalt lava flows which poured out from a crater east of Mt. Surprise in North Queensland, only about 190 000 years ago. They are part of the geologically-young McBride Volcanic Province, which contains about 160 volcano remnants, with Undara Volcano being the third youngest.
The Undara volcanic crater is 340 m across and 49 m deep, rising only 20 m above the surrounding lava field. It has an elevation of 1100 m, being the highest point in the McBride Province. An estimated 23 km3 of lava erupted from Undara Volcano. Most of this was of the 'pahoehoe' or ropy lava type, flowing at a temperature of about 1200° C and blanketing about 1550 km2.
The lava field extends 90 km to the north and 160 km to the north-west of the crater (the world's longest lava flow from a single volcano). Some of the lava flowed down old water courses, and while channelled in this way, hardened on the outside, while still flowing inside the tube thus formed. When the lava stopped flowing, long, hollow lava tubes, or lava caves were left. Most of the tubes are less than 200 m long, but one is over 1.3 km (Australia's longest lava tube cave).
The largest lava tube, Barker's Cave is 35 km from the crater, with a length of over 560 m and ceiling height of 13.5 m. Many of the tubes have stalactites ('lavacicles') formed from lava drips from their ceilings. Over 60 lava tubes and arches (collapsed tubes) have been found in this system of lava flows.
Copyright © Australian Museum, 2004