September 2, 2010
A weekly feature provided by scientists at the Hawaiian Volcano Observatory.
A new book reintroduces old terminology
There's a new volcanology book available from a Hawai`i-based volcanologist, the first in almost 40 years.
Volcanoes: A Global Perspective was written by John P. ("Jack") Lockwood and Richard W. ("Rick") Hazlett. Jack retired after a long career with HVO and is now an internationally known consulting volcanologist. Rick wrote and illustrated several field guides about Hawai`i and has been a long-time geology professor at Pomona College, California. Their combined efforts result in a well-illustrated, broad treatment of modern volcanology that provides the reader with a good understanding of how volcanoes work.
Of special interest are stories with Hawai`i ties, like the origin of the term "pyroduct." The first person to theorize how lava is able to travel so far from its vent was not a geologist but a Christian missionary—the Reverend Titus Coan—who was very interested in the workings of active volcanoes. Reverend Coan was stationed in Hilo between 1835 and his death in 1882, and witnessed every eruption of Mauna Loa during that time.
His first was the January 1843, eruption of Mauna Loa that sent flows racing to the north where it ponded against cinder cones at the base of Mauna Kea in the Saddle between the two great mountains. Having never climbed either mountain or seen an active Mauna Loa lava flow, Coan, with another missionary and a few native porters, decided to make the trip.
After an exhausting journey to the foot of these active flows, the party began a treacherous climb over hot, but hardened, lava flows in an attempt to reach the vent high on Mauna Loa. On the way, Coan's party noticed openings (now called skylights) through which they could see a molten lava stream below, flowing at a rate of 20 miles per hour. They found several of these openings on their trek up the lava flow.
Unencumbered by the constraints of a formal geologic education, he concluded that "As these lower branches [of the flow] were pushing slowly along upon level ground, and as the feeding flood had ceased to come down upon the surface from the ... vent, but flowed in a subterranean duct or ducts ..."
Titus Coan humbly offered a name "pyroduct" for these conduits through which lava flows.
Coan's observations, however, were not without controversy, as he discovered upon discussed his ideas with the premier American geologist, James Dwight Dana. Dana had been the geologist with the U.S. Exploring Expedition that visited Mauna Loa and Kilauea volcanoes in 1840 and 1841.
As the story is told in Volcanoes: A Global Perspective, Dana, who had never observed an active Hawaiian lava flow, openly challenged and dismissed Coan's ideas that lava flowed through the hardened interior of flows and hypothesized that what Coan had seen were deep volcanic fissures radiating from Mauna Loa's summit.
Coan's idea, however, made more sense to other lava flow witnesses, and the reports of subsequent eruptions by fellow missionaries also included descriptions of pyroducts. Even if the term wasn't used, the idea of internal lava transport had become widely accepted in Hawai`i.
For example, when another Mauna Loa lava flow threatened Hilo in the summer of 1881, newspapers reported plans for diverting lava away from the town and the bay. In the August 20, 1881, edition of The Saturday Press, the rationale was given this way for a potential use of explosives:
"For the last two months nearly, has this flow poured down the mountainside, and it seems to make for itself a tunnel or casing, of cold lava, whilst this heated molten rock flows in a sort of tube of its own construction.?Now if this great conduct were broken up the lava flow might be taken in hand as it were, rendered a little more tractable."
Titus Coan's idea made it possible to think of ways to divert a lava flow, Dana's ideas did not. Years after Coan's death, Dana did, finally, accept Coan's concept. As Jack and Rick say in their new book, "Good field observations usually trump academic theories!"
Flash forward to 2010, Pyro-ductTM is now an electrically and thermally conductive material that is commercially available, and the internal conduits through which lava is transported are commonly called "lava tubes." But, who knows, maybe the new text will return Coan's term—"pyroduct"—to modern usage.
Kīlauea Activity Update
No breakouts on the flow field have been reported over the past week, as of this writing (Thursday, September 2). Though repeated deflation-inflation cycles at Kilauea's summit may have caused small fluctuations in the size of the steam plume at Puhi-o-Kalaikini, the ocean entry remains active.
At Kīlauea's summit, a circulating lava pond deep in the collapse pit within the floor of Halema`uma`u Crater has also been visible via the Webcam throughout the past week. The lava surface fluctuated slowly in concert with the deflation-inflation cycles. This slow change in lava level was punctuated on several occasions by abrupt increases in the height of the lava surface. These periods of high lava level were short-lived, lasting up to several hours, and ended with a sudden drop of the lava surface, back to its previous level. Volcanic gas emissions remain elevated, resulting in high concentrations of sulfur dioxide downwind.
One earthquake beneath Hawai`i Island was reported felt during the past week. A magnitude-2.8 earthquake occurred at 8:40 p.m. on Thursday, August 26, 2010, H.s.t., and was located 14 km (8 miles) west of Kilauea summit at a depth of 11 km (7 miles).
Visit our Web site (http://hvo.wr.usgs.gov) for detailed Kīlauea and Mauna Loa activity updates, recent volcano photos, recent earthquakes, and more; call (808) 967-8862 for a Kīlauea activity summary; email questions to askHVO@usgs.gov.
Updated: September 7, 2010 (pnf)