Archive for May, 2010

Mount St. Helens 30 Years Ago

May 18th, 2010 -- Posted in Volcanoes | No Comments »

Mount St. Helens eruption

May 18, 1980 was a day we will all never forget. Who expected the beautiful mountain, where thousands hiked and camped each year, could unleash such deadly force? The Weather Channel commemorates the catastrophic eruption in an anniversary slideshow.

In case you don’t remember the powerful forces released that day, here’s some numbers to think about. A magnitude 5.1 earthquake preceded the collapse of the mountain peak. Pyroclastic  flows wiped out everything in it’s path including 250 miles of forest land and raised Spirit Lake’s water level by 200 feet. 520 million tons of ash swept across the country. 57 people died and over 200 homes were destroyed in the worst volcanic disaster in the United States.

The USGS had been monitoring Mount St. Helens for months. USGS volcanologist David Johnston reported the eruption, but he was one of those who lost their life that day. Still, scientists learned much from the eruption, from data they had never collected before, from a volcano they had been studying prior to the eruption, and a volcano they continue to study today.

Earthquakes in the Middle Ages

May 14th, 2010 -- Posted in Earthquakes | No Comments »

Faultline

I read a recent blog post over at Medieval Minds about Catalonia earthquakes of the XIV and XV centuries. Author Ann Scott, who is a medieval historian, sites a book, Historical Seismology, that features a study of the Catalonia (NE Spain) quakes. The study, which concluded in 2006, was conducted to evaluate the potential seismic hazard and to evaluate the quakes using standardized criteria. The findings were reported at the First European Conference on Earthquake Engineering and Seismologythe same year in Geneva, Switzerland. In the XIV and XV centuries, only eight earthquakes of magnitude 5.0 or higher occurred, with the largest at magnitude 6.5 occurring in 1428.

I wasn’t sure why the study was barely taking place in 2006, but as I thought about Scott’s post, I was reminded of the value of scientists studying the seismic history of a region. While earthquakes can’t be predicted yet, research provides fault history and field analysis that helps geologists estimate earthquake probabilities. Armed with evidence of a probability of a large quake, scientists and authorities are better able to convince citizens to prepare themselves.

Wall Street Journal Charts Largest Volcano Eruptions

May 8th, 2010 -- Posted in Volcanoes | No Comments »

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.

Iceland Volcano Causing Earthquakes

May 7th, 2010 -- Posted in Earthquakes, Volcanoes | No Comments »

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.”

Chile Earthquake Update

May 2nd, 2010 -- Posted in Earthquakes | No Comments »

Why has the Chilean earthquake disappeared from our radar? Is everything fine and well? Have things returned to normal in Chile? Strong aftershocks struck after the 8.8 magnitude earthquake that occurred on February 27, 2010, lasting 90 seconds and leaving hundreds dead. Since then, more than 1.5 million people have been displaced. According to those who experienced the quake, “cars lay mangled and upended on streets littered with telephone wires and power cables. A new 14-story apartment building fell.” With more than two-dozen significant aftershocks, Chile has to be in turmoil.

Did you know the ensuing tsunamis killed 500 people and caused $30 billion in damage? The earthquake triggered a tsunami which devastated several coastal towns in south-central Chile and damaged the port at Talcahuano. Tsunami warnings were issued in 53 countries, causing minor damage in San Diego and Japan.

Just hours ago, on May 2nd, USGS reported earthquakes in Chile and elsewhere in South America. And Reuters reported a 5.8 magnitude earthquake hitting central Chile. That quake was felt in Santiago but there were no reports of damage.

Sadly, it seems it will be a quite a while before things return to normal in Chile.