Bare Life on Molten Rock

She laughs to herself, and her whole body shakes with it—she's got a volcano to choke off. So she curls the fingers of one hand into a fist, and sears down its throat with her awareness, not burning but cooling, turning its own fury back on it to seal every breach. She forces the growing magma chamber, back, back, down, down …

N.K Jemisin, The Fifth Season, 384

We know surprisingly little about rock. Rock is red-hot, creeping, viscous stuff that we rarely see, and touch at our peril. For living things like us to enter into an intimate relationship with the lithic - to become enmeshed with rock - is to become rock. It is to meet with sudden, certain, cessation of life.

At least, that's how it would be if we could encounter the bulk of the Earth's rock. Around 15% of Earth's mass is made up of a metallic core, which geoscientists estimate to have a temperature range between 4400°C and 6000°C. Most of the rest of the planet—some 84% of its volume—is comprised of the mantle: a slowly churning mix of more-or-less solid rock with temperatures ranging from around 1000°C nearer the surface to 3700°C closer to the core. There are some bizarrely hardy beasts on this planet, microorganisms that have spent billions of years learning to live with high heat. But even the most 'hyperthermophile' bacteria can only tolerate temperatures of 120°C, a degree of magnitude lower than what would be needed just to brush up against the vast majority of the planet's rock.

There is, of course, an exception to the unlivable cauldron that is earthly rock. A small proportion of the rocky material of the mantle—at any moment some 1% of the planetary body—has made it to the Earth's surface. Here, it cools and hardens in a thin, brittle, excrescence that geoscientists call the crust—an outer coating about which they know a great deal more than all the other layers combined. In its exile from the Earth's simmering interiority, crustal rock provides a platform and venue for biological life. Living things can approach, engage, even ingest this minority of minerals. Indeed, here rock and life transform each other, generating composite formations—rocks assembled out of once-living bodies, biological bodies composed in part of minerals. But we should not forget that this florid organic-inorganic interface is but a 'gloss on the surface' of our astronomical body (Fortey 415), and that the stone that invites life's embrace is a chilled and pallid shadow of its seething progenitors.

For perhaps four billion years, life has been denied direct access to its deep wellspring, its basal underpinning. That may be changing. During exploratory drilling of geothermal wells in Iceland's Krafla volcanic caldera in 2009, engineers accidently made contact with magma. 'Magma' in geological terminology refers to any molten rock. Along active fault zones, magma regularly intrudes into the Earth's crust, where it collects in pockets or 'chambers,' and occasionally bursts through to the surface. At just over two kilometers down, Krafla's magma body was higher than expected, and the fact that the encounter did not have explosive consequences has attracted attention from volcanologists and geothermal engineers worldwide (British Geological Survey).

Researchers are interested in the geothermal potential of magma chambers, which could generate up to ten times the energy of conventional boreholes. More speculatively, the new international research facility at Krafla has begun to explore the possibility of placing sensors directly into magma and even deliberately cooling molten rock—with implications for meliorating volcanic hazards. The research team has no illusions about the trouble they might be stirring up—being at once aware of the 'spectacular' danger of triggering eruptions and the more insidious risk of mobilizing harmful subterranean chemical elements such as mercury and arsenic. "In spite of studies of the magma, well testing and modeling," geologists report, "the thermo-hydraulic nature of the reservoir at Krafla has remained enigmatic" (Scott et al. 2).

'Enigmatic' is an understatement. Only twice...