Iceland

Iceland Volcano Blows a Smoke Ring

A very rare event was captured on film when the Eyjafjallajokull volcano in Iceland blew a smoke ring. According to a story in a London newspaper, the Mail Online, this was witnessed by Joseph Licciardi, an earth sciences professor from Oregon State University.   This event occurred on May 1. The video below is a ring from Mt. Etna in June, 2000.

See the ring develop: http://www.youtube.com/watch?v=VbV98Z0QP-k

Smoke-ring-150x59

Some Fallout from Icelandic Volcanoes

A story on the Scientific American website proclaims “Ice cap thaw may awaken Icelandic volcanoes.” “A thaw of Iceland’s ice caps in coming decades caused by climate change may trigger more volcanic eruptions by removing a vast weight and freeing magma from deep below ground, scientists said on Friday.”

This contention is based on the fact that rocks melt at a lower temperature under lower pressure. The question is, will removal of some or all of the ice cap in Iceland result in a pressure load decrease that will make a significant difference in melting temperature and therefore produce more magma?

The relationship between pressure and melting temperature of basaltic lava, the type in Iceland, was estimated by the Carnegie Geophysical Laboratory to be:

Tm = 1391.5 + 0.01297 * P

Tm is the melting temperature in degrees Centigrade, and P is the pressure in bars (or atmospheres, 1 atmosphere = 1.01 bars or about 14.7 pounds per square inch at sea level). We need be concerned only with the last term of that formula which says that a one atmosphere change in pressure results in a 0.013º C change in melting point (rounding the number to two significant figures).

The pressure of one atmosphere is about equivalent to the pressure or weight of 10 meters of ice, so one meter of ice would result in a temperature change of about 0.0013º C. The thickest ice in Iceland is about 500 meters. Complete removal of that ice would lower the melting point of rock about 0.65 ºC, not very significant considering the base melting point is nearly 1400 ºC. The earth’s normal geothermal gradient (the change in temperature with depth), is about 20- to 30º C around most of the planet, and about 40º C at tectonically active spots like Iceland. The removal of 500 meters of ice giving a temperature difference of 0.65 ºC is the equivalent of a depth difference of about 16 meters. Big deal. It is very unlikely that this small pressure difference would stimulate additional volcanic activity.

Ash is formed when magma is rapidly cooled and fractured by steam. Removal of the surficial water source could result in less ash formation and make the Icelandic volcanoes behave more like the Hawaiian volcanoes.

Reference:

Change of Melting Point of Diopside with Pressure, by Hatten S. Yoder Jr., Geophysical Laboratory, Carnegie Institution of Washington, © 1952 The University of Chicago Press.

Another type of fallout:

The banning of air travel in Europe, which is causing economic chaos, was based on predicted damage to aircraft from ash clouds. The ban was based on an advisory from the British Meteorological Office’s London Volcanic Ash Advisory Centre. That organization based their advisory on a computer program originally developed to monitor nuclear fallout. The computer model predicted dangerous concentrations of ash at various places around Europe. The Met office failed to send up any weather balloons to check actual conditions. Because there is a valid possibility that flying through an ash cloud can damage aircraft, the major airlines made test flights in the last few days to check conditions and found no danger. This is another example showing that relying on computer modeling, rather than real data, can cause unnecessary economic loss and concern.

Geologic Setting of Icelandic Volcanoes

The ash spewing from the Eyjafjallajokull volcano in Iceland is disrupting air traffic throughout Europe. Volcanic ash is essentially sharp-edged glass with particles ranging from sand-sized to microscopic. These particles can wreak havoc with jet engines and your lungs. The last time this volcano erupted, the eruption lasted more than a year, from December 1821 until January 1823.

Iceland sits astride the Mid-Atlantic Ridge, a boundary between two tectonic plates, where new crust is being formed by volcanic eruptions as the plates diverge, i.e., they are moving away from each other. Movement on this structure over the last 180 million years or so has separated Europe from North America, and Africa from South America. The island of Iceland is engaged in a geologic race between the spreading motion which is ripping the island apart, and the volcanoes which are building the island up.

Other islands of the Atlantic Ocean created by the volcanism of the Mid-Atlantic Ridge are The Azores, Bermuda, Madeira, The Canary Islands, Ascension, St. Helena, and Tristan da Cunha. But, you probably haven’t heard about any volcanoes erupting in Bermuda because that island group lacks one other geologic phenomenon: the “hot spot.” Iceland also sits above a mantle plume or “hot spot” where magma from deep in the mantle forces its way to the surface. The Hawaiian Islands were formed, and are being formed, by such a hot spot. In Hawaii, the westward movement of the Pacific plate passes over this hot spot and eruptions produce new islands. Iceland, however, is not moving in such a manner.

map_plate_tectonics_world

The general geology of Iceland is shown on the map below from the Nordic Volcanology Institute.

Iceland-geo_map

The pink area on the map represents the rifts along the Mid-Atlantic Ridge where the crust is separating and the volcanoes are most active. Of Iceland’s 100 most active volcanoes, 25 have erupted in recent history, and 35 volcanoes have erupted in the last 10,000 years. Eleven volcanoes have erupted between 1900 and 1998. Most of the eruptions were from fissures or shield volcanoes and involve the effusion of basaltic lava.

The 1783 to 1784 eruption at Laki fissure and the adjoining Grímsvötn volcano was the largest single historic eruption of basaltic lava (12 cubic km). Benjamin Franklin, who at the time was serving as ambassador to France remarked on this eruption. The ash cloud caused the “year without summer.” That eruption of basalt lava and clouds of poisonous hydrofluoric acid/sulfur-dioxide compounds killed over 50% of Iceland’s livestock population, leading to famine which killed approximately 25% of the population. It remains to be seen if the current eruption will be as long lasting. So far, the ash cloud from the current eruption has risen to 30,000 feet which affects airline travel, but it has stayed below the stratosphere, so the climate effects are not likely to be as drastic as those in 1783.

The Boston Globe has a series of photographs of the volcano and flooding it caused. Boston Globe photos: http://tinyurl.com/y6vslk4