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Volcano Watch: Will drilling into magma start a volcanic eruption?

Krafla volcanic area, Iceland

Krafla volcanic area, Iceland

(Volcano Watch is a weekly article written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.)

It seems logical that if underground magma can start an eruption by forcing its way to the surface, one might also start an eruption by opening a conduit from the surface to the magma. While plausible, that doesn’t seem to be what happens.

Magma has either been drilled into—or risen to enter—a drill hole four times, according to the scientific literature. Of the four incidents, three occurred in Iceland and one in Hawai`i with one of the Icelandic examples producing a brief spattering of lava. In all of the examples, the wells were not destroyed and continued to be used for their original purpose afterward.

Lava flow during a rift eruption at Krafla volcano, northern Iceland, in 1984. Photo courtesy of USGS

Lava flow during a rift eruption at Krafla volcano, northern Iceland, in 1984. Photo courtesy of USGS

The first known encounter was in September 1977, in a geothermal area south of Krafla volcano in Iceland. Hole B-4 was drilled to 1,138 m (3,734 ft) in 1968 and had been producing hot water and steam for the Namafjall geothermal plant before the incident. The sequence started with a small amount of lava erupted in the northern part of the Krafla caldera during a rifting event, and it was followed by a migration of earthquakes to the south, directly toward the plant and the well field that included B-4.

The earthquake swarm allowed the tracking of an injection of magma along dikes to the south. The earthquakes arrived in the Namafjall area about 10 pm and, about 40 minutes later, a large crack opened that cut the main road. At 11:45 pm, a loud explosion was heard when one of the pipes carrying steam from the well burst. It was followed 10-20 minutes later by a series of rapid explosions or shots (bursts?) of glowing cinders, carried upward by steam jetting from the ruptured pipe that lasted about one minute.

It was later found that the magma was injected into the drill hole between depths of 625 and 1,038 m (2,050 and 3,405 ft). The eruption produced only a few cubic meters (cubic yards) of lava spatter. Well B-4 was none the worse for the experience and, once the casing was repaired, continued in production until 2002.

The next three were less dramatic but equally interesting scientifically. Each was an instance of drilling into magma, and two of them were also in the Krafla volcanic zone. In 2008, well K-39 drilled into a glass at about 2.6-km (1.6-mi) depth. The glass had probably been molten magma but was rapidly cooled by the drilling fluids before the actual encounter. In 2011, magma flowed into an exploratory geothermal well (IDDP-01) drilled into the center of the volcano at 2.1-km (1.3-mi) depth.

The fourth example occurred in the only geothermal development in Hawai`i and involved drilling into the lower east rift zone of the active Kilauea Volcano. In 2005, the Puna Geothermal Venture guided the KS-13 drilling operation into a molten magma body at 2.5-km (1.6-mi) depth beneath the Pu`u Honua`ula Cone and very close to the initial fissures that opened during the 1955 eruption of Kilauea.

Upon analysis, the magma turned out to be dacite – a type of magma very different from the normally basaltic lavas that erupt from Kilauea Volcano. While the main component of almost all magmas is silica (the stuff that window glass is made of), dacite has a lot more of it than basalt.

So where’d the dacite come from? We know that, during any eruption, not all of the magma that is transported through the volcano gets erupted. A significant portion is left within the rift zone. That magma slowly starts to cool and form crystals; because the crystals don’t use up the silica in the same proportion that exists in the magma, the remaining liquid magma becomes slowly more silica-rich.

Understanding this process helps us “see” where these magma storage areas are. When new eruptions occur, like that in 1955, for example, the first lavas usually contain small amounts of these stored lavas. That’s because the new magma rose through these storage areas and carried some of the remaining more silica-rich magma along with it. As the eruption progresses, the lavas usually become “fresher” or more like the stuff that is originally supplied to the volcano.

There are several of these local storage areas within Kilauea volcano’s east rift zone and, based on these four examples, it doesn’t appear that drilling into one of them will start an eruption.

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