• Matthew Blackett

Drill volcanoes, release the pressure?

Those cooks amongst us will be aware of the safety valve on a pressure cooker: once the pressure inside gets past a certain threshold, the valve opens and steam comes out. Without such a mechanism, pressures inside might reach a critical point, the cooker would explode and we'd end up with stew covered walls. Based on this analogy, the question has often been asked: can't we just drill into a #volcano to release its internal pressure and thus, prevent #eruptions and rock/#lava splattered landscapes?

In theory, this sounds like a great idea: we could manage the pressures within volcanoes and in effect, de-gas or de-magma them at our convenience. If we could do this, it would avoid the complications that come with unpredictable eruptions and we could potentially save many lives and reduce the associated economic impacts. In fact, between 1989 and 1998, a drilling project in Long Valley, California, attempted to reach the region's magma but failed. So might this pressure release actually work? Most scientists agree it would not!

The magma (i.e. lava whilst under the surface) of a volcano is stored in its magma chamber and is often termed #mush, referring to its make up of some solid crystals suspended within a liquid-phase mass of molten rock. While underground and at the associated high temperatures and pressures, this 'mush situation' is maintained (much like water being kept in the liquid phase at temperatures >100°C in a pressure cooker). If we were to drill into the magma chamber however, the sudden loss of pressure and temperature once the magma was exposed to the environment, would lead to the immediate solidification of the molten material and thus, to the blockage of the hole we had drilled.

A volcano and its underlying magma chamber (US NPS).

This scenario of blocking a drilled hole with solidified magma is not just a theoretical situation. In 2005, a drill from the Puna Geothermal Venture on the Big Island of Hawaii (initially developed in the 1970s to harness the island's geothermal heat) unexpectedly stuck magma at a depth of around 2400m and a temperature of around 1050°C. In this case, the magma flowed up the 'pipe' just several metres before solidifying into a glassy substance, obsidian, and preventing the outward movement of magma or gas. Whilst this event was unplanned, it has since provided geologists with the unprecedented opportunity to study magmatic processes, with one scientist quoted as saying:

"This is unprecedented; this is the first time a magma has been found in its natural habitat. [] Before, all we had to deal with were lava flows; but they are the end of a magma's life. They're lying there on the surface, they've de-gassed. It's not the natural habitat. It's the difference between looking at dinosaur bones in a museum and seeing a real, living dinosaur roaming out in the field."

The entrance to the Puna Geothermal Venture Power Plant on the Big Island of Hawaii (source).

Similarly to Hawaiian experiences, drilling at the Krafla Power Station on Iceland's Reykjanes Peninsula (near where the current volcano is erupting) also unexpectedly reached magma in the search for geothermally-heated water, this time in 2009. Here, where magma solidification also happened, the project has continued as the The Iceland Deep Drilling Project, with the aim of better understanding Iceland's geothermal systems and, associated with it, the Krafla Magma Test Bed (KMTB) has been created. The KMTB has been developed with the aim of better understanding magmatic (and hence volcanic) processes, via boreholes (40+) often right into, or near to, known magma chambers. One of the aims of the project is summarised as:

"By drilling through the rock–magma interface and into magma, we can establish where and under what conditions magma is stored beneath a volcano. Stimulate its boundary region by fluid injection to see whether the result is indeed measurable as the inferred unrest and ultimately place sensors near and even in magma to provide direct measurement of a rise in temperature, extent of crystallisation, change in gas content or increase in pressure that could lead to eruption".

Krafla Geothermal Plant (source).

So whilst we are never likely to be able to drill into a magma chamber to de-pressurise it and to prevent a forthcoming eruption, drilling efforts will continue so that we can better understand what goes on 'down-there'. Given such an enhanced understanding will enable scientists to model different scenarios and to thus potentially formulate predictions based on the empirically collected data from deep within the Earth. And, let's face it, even if we could extract the content of magma chambers in a controlled way, perhaps via heated pipes, so to reduce pressure build up, what would we do with many cubic kilometers of molten rock and gases that would be emitted? These products would likely be more hazardous than the volcano we're trying to tame - so such endeavours are probably best left to fiction writers!