New Auckland Lava Cave Discovered

Did you know that lava flows can create their own underground tunnels?
Lava flowing in these “lava tubes” is so insulated that it only loses ~1 degree every kilometer it travels – super efficient! The lava cools as it flows away from the vent forming a crust of hard basalt. Hot lava continues to move inside the flow and eventually drains leaving an empty lava tube behind. Lava tubes are a common feature in Auckland, and are sometimes found during construction projects.
Our partners at Auckland Council invited us to help photograph and take rock samples from one of several new lava tubes recently discovered in the city. This task was quite an adventure, as it was not safe to enter the tube. The samples we took will be geochemically analysed to try to figure out which volcano it flowed from, and the samples and tube descriptions can also be used to learn more about lava flow lengths and properties in Auckland. DEVORA also plans to do more research on our hidden, subterranean tunnels (stay tuned for an MSc opportunity soon!).
Lava tubes can be fragile and dangerous, with falling rocks and roof collapses (and the occasional Wilberforce!). If you are in Auckland and want to most safely get a look at a lava tube yourself, check out the excellent examples along Rangitoto’s Lava Caves Track – and don’t forget your torch!
Pic 1: New lava tube discovery in Auckland! (Half of a) Person for scale. As one side is blocked, this is now a lava tube cave. The small cave’s entrance is approximately 1 m at its widest and is overlain by a mixture of weathered tuff and blocks of lava. A crack in the ~0.5 m lava block to the top left of the entrance shows how fragile the cave is. Unfortunately concrete covers a portion of the tube entrance and floor. The cave expands back and curves around to the right several meters before being blocked off.
Pic 2: Sandeep (left) and photographer Jay (right) take photos of the tube’s interior from the entrance. Sandeep held the photography light while Jay took the photos on a pole-mounted camera. It took a lot of careful maneuvering to get good shots without entering the lava tube
An interesting feature of this lava tube is the ‘petal’ like sheets peeling off along the roof and sides of the tube. More research needs to be done to figure out how these formed. Stay tuned with DEVORA for more lava tube news!