2:45 PM | The Iceland volcano erupts, but a far bigger explosion occurs on the other side of the world

[Ash plume from Rabaul volcano in Papua New Guinea]

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Summary The Bardarbunga volcano in Iceland that we have been tracking in recent days has finally erupted, but it was not a big explosive event. Meanwhile, there has actually been a far bigger eruption in Papua New Guinea at the Rabaul volcano on Mount Tavurvur and this has the potential to do more damage to nearby population centers. In addition to the direct threat to people in nearby locations, volcano eruptions can produce ash that is extremely hazardous to jet aircraft that inadvertantly fly through it. The ash is composed primarily of silicate particles that melt when ingested into the combustion chamber of a jet engine, causing severe loss of engine performance and perhaps, a complete shutdown of the engine.

Iceland The Iceland volcano which sits beneath a glacier has been receiving most of the attention lately and last night it finally started erupting as lava emerged from a fissure. A fissure eruption is one in which lava essentially flows up through vents in the ground spread out over a larger area. The eruption lasted about four hours and came after weeks of earthquakes in the region. The eruption did not spew ash into the atmosphere and has had minimal effects on flights and it is in a relatively remote area of Iceland. Even though the eruption has stopped for the time being, earthquakes continue to rumble indicating magma is still on the move, and this volcano will continue to be closely monitored. By the way, in an odd twist of fate by Mother Nature, the remains of Hurricane Cristobal raced from off the US east coast into the North Atlantic during the past couple of days and actually dumped some serious snow on Iceland as well as on eastern sections of Greenland.

Papua New Guinea Meanwhile, on the other side of the world, the large Rabaul volcano began erupting earlier today and it has spewed out plenty of ash into the atmosphere. The ash plume has apparently reached about 11 miles into the air and has indeed disrupted air travel in that part of the world. This was the first major eruption of this volcano – one of the most active in Papua New Guinea - in about twenty years. In 1994, an eruption there nearly destroyed Rabaul altogether, forcing residents to flee.

Impact Volcanic eruptions along with oceanic and solar cycles play crucial roles in our global climate. The most substantive climatic effect from volcanoes results from the production of atmospheric haze. Large eruption columns inject ash particles and sulfur-rich gases into the troposphere and stratosphere and these clouds can circle the globe within weeks of the volcanic activity. The small ash particles decrease the amount of sunlight reaching the surface of the earth and lower average global temperatures. The sulfurous gases combine with water in the atmosphere to form acidic aerosols that also absorb incoming solar radiation and scatter it back out into space. In fact, the formation of atmospheric sulfur aerosols has a more substantial effect on global temperatures than simply the volume of ash produced during an eruption.

Not only does the type and amount of ash from volcanic eruptions play a critical role in its potential effect on global temperatures, but the location of the eruption is also very important. Volcanic eruptions in the tropics, for example, can be much more important than those in the mid-latitudes for a couple of reasons. First, the sun heats equatorial regions more than in mid-latitude or polar regions; therefore, any disruption to solar radiation in the tropics can have more serious effects on global temperatures. Second, upper level winds - which act to spread and disperse ash plumes – are typically weak over tropical regions as compared with the mid-latitudes, for example, and this could impact the longevity of any ash cloud in a particular region.

The atmospheric effects of volcanic eruptions were confirmed by the 1991 eruption of Mount Pinatubo, in the Philippines. Pinatubo’s eruption cloud reached over 40 kilometers into the atmosphere and ejected about 17 million tons of SO2, just over two times that of the El Chichon, Mexico volcano in 1982. The sulfur-rich aerosols circled the globe within three weeks and produced a global cooling effect approximately twice that of El Chichon. The Northern Hemisphere cooled by up to 0.6 degrees C during 1992 and 1993.