Credit: White Island Tours
I'M STANDING ON the crater rim of White Island, New Zealand's most active volcano. Clouds of sulphurous steam veil the marbled green waters of the lake below. The entire area hisses and boils like a witch's cauldron. With an acidity of about pH 0.2, the crater lake is one of the most acidic environments on Earth. Yet even here primitive algae and bacteria thrive.
I've visited New Zealand twice before and been blown away by the scenery, featured in films from Lord of the Rings to The Piano. But this trip, I'm on a mission to some of the geological hot spots, which have produced this remarkable terrain. New Zealand is a Mecca for geologists. Processes that elsewhere on the planet have been frozen by the unrelenting aeons are still in action here.
It is one of the few places on Earth where a plate boundary - the line demarking the collision of two massive tectonic plates - is accessible on land, rather than buried out to sea. The colliding plates meet in a subduction zone, where the thinner oceanic crust of the Pacific Plate is pushed underneath the Indo-Australian Plate.
As the Pacific Plate dives into the mantle, minerals under intense heat and pressure release water, which permeates up into rocks of the overlying plate, causing these to melt. This melted rock forms subterranean magma chambers in the crust, instigating volcanism on a widespread and spectacular scale.
"We're surrounded by volcanoes in New Zealand and it's exciting to work in an area that is so active - it's one of the reasons I became a volcanologist," says Jan Lindsay from the Institute of Earth Science and Engineering at the University of Auckland. "The area north of Auckland is peppered with old volcanoes. There's also Little Barrier Island in the Hauraki Gulf, and the Coromandel Peninsula is formed by old volcanoes too."
The most recent, and most massive, eruptions in New Zealand have all been found in what volcanologists call the North Island's 'Taupo Volcanic Zone' (TVZ), a 250-kilometre-long frontier of intense volcanism, stretching from the central Taupo region north to White Island, 48 km out from Whakatane in the Bay of Plenty.
White Island and Mt Ruapehu are the two most active volcanoes, venting ash, gas and occasionally lava. Ruapehu is found on the southern side of Lake Taupo. It erupted as recently as September 2007, accompanied by a 2.9 magnitude earthquake, and even more spectacularly between 1995 and '96.
White Island is a stratovolcano, a cone-like volcano, mostly submerged by the ocean and created about 150,000 years ago as magma formed by the subducting Pacific Plate punched through the seafloor. It has been erupting gas, steam, lava and rock fragments since at least 1826, when the first Europeans set foot on the island.
Getting out to the island summit of the marine volcano isn't always easy - access by boat is restricted in bad sea conditions, and on the night I arrive in Whakatane, on the mainland, the wind picks up and the swell is rising. I'm told the skipper will make the call about leaving in the morning.
Nervous, but packed and ready, I discover at 8:00 am that the trip is off. To bide my time while hoping the weather will improve, I drive 100 km southwest to Rotorua, New Zealand's most famous geothermal region, and do what every tourist here does.
A light mist of rain plays on my face as I steam my skin in a thermal spa. I lazily move through the three pools, from nicely warm, through nicely warmer to satisfyingly scalding. The soak may cost money, but the energy heating the water is free: all of the heat that permeates the area originates in the TVZ's geological activity.
