May 8th, 2010 -- Posted in Volcanoes |
Pelee Volcano
Last month the Wall Street Journal produced an interactive graphic to show the major volcanic eruptions within the past 200 years. I noticed a major volcanic eruption missing from the cool timeline and I was ready to call the Wall Street Journal to report their mistake. Surely Mount Pelée’s eruption in 1902 was omitted in error. That eruption on the pristine Caribbean island of Martinique killed more than 30,000 people. Pyroclystic flows, volcanic gases, and ash from the stratovolcano completely destroyed the town of Saint-Pierre, the largest city of Martinique.
Before I picked up my phone I referred to my notes, and the USGS web site, of course. And sure enough Mount Pelée’s eruption, even though it is considered the worst volcanic disaster of the 20th century, only has a VEI of 4. How could that be? The USGS themselves say the Mount Pelée eruption was very small, producing only about 3 percent of the volume of ash ejected during the May 1980 eruption of Mount St. Helens.
With the VEI measuring only Magnitude (measures the amount of lava produced), and Intensity (measures how fast the lava is produced), some of the most destructive eruptions have not been “very large.” It’s no wonder that some scientists are arguing for a change in the VEI to add other measurements such as levels of destruction and loss of life.
May 7th, 2010 -- Posted in Earthquakes, Volcanoes |
Ash plume from Eyjafjallajökull
Updates from the Institute of Earth Sciences at the University of Icelandreport that at least 10 earthquakes have been located at Eyjafjallajökull since midnight. Most are less that magnitude 2. Measurements show continued horizontal displacement around Eyjafjallajökull volcano. Explosive activity has increased, and with considerable tephra fallout, the cinder cone continues to build. Dark ash plumes have been observed at hieight of 20,000 – 22,000 feet. Scientists have reported, “everything turned black”. The lava channels are about 30 – 60 m wide. And according to UPI, Iceland’s volcano roared back to life on Thursday. “The eruption has changed back to an explosive eruption, lava has stopped flowing and most of the magma gets scattered due to explosions in the crater,” the Icelandic Meteorological Office said.
Will more disruptions in air travel occur? Will Eyjafjallajökull volcano return to the eruptive intensity it displayed in April? Scientists continue to say that “there are no signs the eruption is about to end.”
April 30th, 2010 -- Posted in Volcanoes |
Mount Fuji, a stratovolcano
Of the four types of volcanoes, let’s take a close look at the dramatic stratovolcano.
1. Frequent pyroclastic eruptions give stratovolcanoes their towering cone shape.
2. Eruptions can originate from the summit or flank vents.
3. Subduction-zone stratovolcanoes, like Mount St. Helens, typically erupt with explosive force.
4. Some of the most powerful and destructive volcanoes in human history have been stratovolcanoes.
5. Stratovolcanoes are the most common type of volcano.
6. Of Earth’s 1,511 volcanoes known to have erupted in the past 10,000 years, 699 are stratovolcanoes.
7. Some of the most beautiful mountains in the world are stratovolcanoes, including Mount Rainer in Washington, Mount Fuji in Japan, and Kamchatka in Russia.
8. Magma, from deep in the Earth’s crust, travels through a conduit within the stratovolcano, which becomes lava when it erupts.
9. Between eruptions stratovolcanoes can be quiet for tens of thousands of years, seeming extinct.
10. Many cataclysmic eruptions throughout history were stratovolcanoes, including Mount Pelee in Martinique, El Chichon in Mexico, Mount Vesuvius in Italy, and Krakatoa in Indonesia, causing catastrophic loss of life.
April 29th, 2010 -- Posted in Volcanoes |
Eyjafjallajökull
Eyjafjallajökull is one of the largest volcanoes in Iceland. Only three eruptions are known at Eyjafjallajökull in historical times, one in 920 A.D., another in 1612 AD, and the most recent in 1821. But on March 20, 2010 Eyjafjallajökull exploded back to life.
According to scientists at the Institute of Earth Sciences Nordic Volcanological Center, today the eruption in Eyjafjallajökull has a continuing discharge of meltwater from Gigjokull Glacier due to ice melt caused by the volcano. Booming sounds have been reported as far as 32 km from the eruption site. While ash and steam rise to an elevation of 3.6 km (12,000 ft), ejected lava reached heights of 660 feet. Would we expect anything less from an active stratovolcano?
Scientists are monitoring Eyjafjallajökull with radar observations, GPS measurements, satellite images, seismic monitors, river gauges, aerial observations, and geologist’s inspections of tephra. Tephra is the term for materials of all types and sizes thrown into the air by a volcanic eruption.