Volcanic earthquakes produce a “seismic scream” just before eruption
By John Timmer | Ars Technica
Volcanic activity is intimately associated with seismic activity. You simply can’t force molten or semi-molten rock through a mountain without cracking a few faults in the process. If we were ever able to understand how to read the seismic activity correctly, it could provide valuable advanced warning about impending eruptions.
A 2009 eruption of Alaska’s Redoubt Volcano may not get us much closer to an advanced warning, but it provides a detailed glimpse of the last moments before an explosive eruption. Shortly before the eruption, small faults within the volcano were breaking so frequently that they merged into what’s being called a "seismic scream." Then, within a few minutes of the eruption, the scream got cut off as the last resistance gave way.
Redoubt is a stratovolcano, built from material that melted as the Pacific plate subducted beneath Alaska. Like some more famous examples, such as Mount St. Helens, it alternates between slow eruptions of extremely viscous rock and sudden, explosive ones. The 2009 eruption was accompanied by a number of small explosions (small at least in the sense that the mountain was still there afterward); the researchers focused on the seismic activity that led up to these explosions.
Most of the earthquakes associated with the eruption were small (between magnitude 0.5 and 1.5) and centered a few kilometers below the volcanic vent. There was plenty of activity of this sort seen during the eruption, but something unusual happened before the largest explosion: "These small earthquakes occurred in such rapid succession—up to 30 events per second—that distinct seismic wave arrivals blurred into continuous, high-frequency tremor." This continuous tremor is what is being called the "seismic scream."
The earthquakes themselves might be enough to make you nervous, but something even more unnerving happened after a few minutes of screaming: things suddenly went quiet. For somewhere between 30 seconds to a minute, the low magnitude quakes stopped, although sometimes larger ones would happen. And then, the explosion hit.
Read the full article at: arstechnica.com
Spectacular Volcanic Plugs & Natural Monoliths
Scientist argues that volcanoes, not meteorite, killed dinosaurs
Scientists locate ’trigger’ for large-scale volcanic eruptions
What if Yellowstone’s supervolcano erupts?
Latest News from our Front Page
German Government Evict Poor Germans From Their Homes For Migrant Asylum Seekers
This is a video of a report on replacement of poor Germans with Middle Eastern asylum seekers. This was made broudcasted on a German Left-leaning TV station on August 28, 2015. It's original title: The most poor of the poor have to vacate their homes for asylum seekers.
Black Lives Matter Radio Host Calls for Killing Whites and Police
â€śItâ€™s open season on killing whites and police officers."
A blogtalkradio program associated with the Black Lives Matter movement spewed racist hate and called for a race war Monday, reports Breitbart.
The YouTube video of the audio recording has since been removed as a violation of YouTube's policy prohibiting hate speech, but Breitbart has video (below) of the host "King Noble" making the comments, taken from ...
Irish will be an ethnic minority in Ireland by 2050
The former President of Dublin City University says that Ireland’s natives will be a minority in the country by the middle of this century...
Professor Ferdinand von Prondzynski was referring to unpublished and unidentified United Kingdom based research. Speaking at the conferring ceremony at DCU on Tuesday he said that the Irish in Ireland will be a minority by 2050 while ...
Immigrant Crisis Is the Final Nail in the EU Coffin
One of the biggest flaws with the EU, was the idea that they could house dozens of cultures with distinct histories and languages, all under one roof, and expect them to thrive. You can’t hold 28 nations together under one union, when all of these countries have wildly different interests, expectations, and priorities. Every time the EU faces a problem, ...
Three-year-old ultra-Orthodox Jewish children told 'the non-Jews' are 'evil' in worksheet produced by London school
Documents seen by The Independent show children are taught about the horrors of the Holocaust when they are still in kindergarten at the Beis Rochel boysâ€™ school in north London.
A whistle-blower, who wished to remain anonymous, has shown The Independent a worksheet given to boys aged three and four at the school. In it, children were asked to complete questions ...
|More News » |