Lesser Known Volcanos of the USA
Posted by Laurie Frost on April 20, 2010
Next month marks the 30th anniversary of the eruption of Mount St. Helens in Washington State. But did you know that in the United States alone there are 169 volcanoes defined as active by the U.S. Geological Survey and that 54 of these are considered to pose a threat to the public? Here’s a map of the 169 from the U.S. Geological Survey [USGS], which is also the source of the map’s caption, as well as the other public domain images and information in this post.
The U.S. Geological Survey (USGS) is responsible for monitoring our Nation’s 170 active volcanoes (red triangles) for signs of unrest and for issuing timely warnings of hazardous activity to government officials and the public. This responsibility is carried out by scientists at the five volcano observatories operated by the USGS Volcano Hazards Program and also by State and university cooperators.
Just this past August (8/20/09), Shishaldin Volcano on Unimak Island, part of Izembek National Wildlife Refuge, Alaska, was erupted. [Photographer: Cyrus Read, U.S. Geological Survey]
In March 2009, another Alaskan volcano, Mt. Redoubt, had erupted, but this incident was relatively mild. Its last significant eruption, one that affected air travel beyond its immediate region, was in 1989-90.
[Image courtesy of the AVO/ADGGS; Image Creator: Janet Schaefer]
The picture and caption below are from the USGS’s Alaska Volcano Observatory.
Image showing the leading edge of a pyroclastic flow that has been channeled down the Drift Glacier into the Drift River valley. This flow is related to an explosive event that occurred at 8:40 [March 27, 2009] ADT, one minute prior to the photo. Image is from a non-telemetered time-lapse camera at Dumbbell Hills. [Image courtesy of AVO/USGS; photographer: Ryan Bierma].
This Landsat image shows Redoubt’s ash cloud last spring:
Landsat 5 image of the Mt. Redoubt area on March 26, 2009 at 1:07 PM AKDT. The false color image shows the large brown ash cloud extending over the Cook Inlet and the western Kenai peninsula (right sid of image). The image also shows a whiter steam and gas plume rising from the summit of Redoubt Volcano (near upper center). Dark lahar deposits extend north from the summit over the Drift Glacier and into the Drift River. [Credit: U.S. Geological Survey]
And did you know that the US Geological Survey has an alert-notification system for volcanic activity? It is like the terrorist alert system, using colors to indicate four levels of concern about volcanic activity: Normal, Advisory, Watch, and Warning [green, yellow, orange, red]. Actually, there are two monitoring categories: Volcano Alert Level and a four-tiered Aviation Color Code.
Just now, six of the seven volcano observatory sites are reporting normal levels. But at the Hawaiian observatory, the status is Watch and aviation advisory is Orange. Its been at this level since summer 2007, however.
Here are some pictures from the Hawaiian Observatory of the lava flow on March 16, 2010 and the active vent in Halema`uma`u Crater on April 2. [Credit: U.S. Geological Survey]
Active volcanos can pose silent, invisible hazards as well. In the 1990s, trees began dying near Mammoth Mountain volcano in the Sierra Nevada mountain range of California, not far from Yosemite. The US Geological Survey at Long Valley Observatory reported:
When the soil was surveyed in 1994 for carbon dioxide gas, exceptionally high concentrations of gas were found in the soil beneath the trees. What caused such high concentrations of carbon dioxide gas? The most likely sources of the carbon dioxide gas include (1) magma that intruded beneath Mammoth Mountain during an earthquake swarm in 1989; and (2) limestone-rich rocks beneath Mammoth Mountain that were heated by the hot magma.
About using the USGS website as a source for public domain images
Here is their policy statement:
USGS-authored or produced data and information are considered to be in the U.S. public domain. While the content of most USGS Web pages is in the U.S. public domain, not all information, illustrations, or photographs on our site are. Some non USGS photographs, images, and/or graphics that appear on USGS Web sites are used by the USGS with permission from the copyright holder. These materials are generally marked as being copyrighted. To use these copyrighted materials, you must obtain permission from the copyright holder under the copyright law.
When using information from USGS information products, publications, or Web sites, we ask that proper credit be given. Credit can be provided by including a citation such as the following:
Credit: U.S. Geological Survey
Department of the Interior/USGS
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