"This is like Jurassic Park for geologists, to see this thing in its natural habitat," said Bruce Marsh of John Hopkins University who, together with Lucien Bronicki of Ormat Technologies and William Teplow of US Geothermal, revealed the findings at the American Geophysical Union's meeting in December. "It's like seeing a dinosaur frolicking in an open field."
The scientists calculate that the magma is likely to be 1050 °C, making the site possibly the hottest commercial geothermal well that has ever been drilled. More typically, a geothermal site could expect temperatures of 500 °C at a depth of 5 km. The large volume of high-temperature rock at such a shallow depth could provide ideal to research heat-extraction methods from volcanic systems for energy generation.
"Although electricity generation is still pretty far away we are excited about getting close to a big source of heat at high temperature," said Bronicki. "We plan to co-operate with the scientific community to learn as much as possible about the resource."
The magma flowed up the drill hole to a height of around 8 metres before solidifying. Engineers from Ormat Technologies, who were sinking a well bore for the Puna Geothermal Venture power plant, repeated the process several times, obtaining around 400 kg of samples of the rock for analysis.
Analysis revealed that the magma was 67% silica, in contrast to the basalt that makes up nearly the entire mass of the Hawaiian Islands, which has a silica content of 50%. The dacite was also higher in potassium and lower in iron than the surrounding basalt.
The Puna Geothermal Venture plant has been producing 25 MW since 1993, roughly 30% of Big Island's electricity requirements. It covers about one square mile of a highly volcanically active area of Big Island.
Geothermal systems extract energy from the Earth's crust in the form of hot water or steam. The hot fluids are used to drive a turbine and create electricity, while the water is injected back into the rock. The technology gives off virtually no greenhouse-gas emissions and is largely renewable. What's more, the electricity-generating plant required has a relatively small carbon footprint compared with nuclear or fossil-fuel power plants because most of the energy capture and extraction takes place underground. Geothermal energy systems currently in use in the US – mostly in California, Hawaii, Utah and Nevada – produce about the same amount of electricity each year as solar and wind power combined. Unlike solar and wind power, geothermal systems can operate continuously to provide firm power and are not dependent on the weather.
The magma discovery was made in October 2005. The scientists announced their findings at the American Geophysical Union Fall Meeting in San Francisco in December.