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**AlaskaDenise** · December 31, 2008, 08:27 PM

Re: Scientists watch unusual Yellowstone quake swarm

Shiloh's reference discusses the "sudden appearanace" of those Yellowstone hotspots. I wonder what caused that? If those conditions should repeat, that may be the trigger for more activity in that area.

The seeming lack of explosiveness of the Hawaiian volcanoes is because they are shield volcanoes (fed by spreading plates).

We've got an area here (Wrangell volcanic field) that is being watched. They're inland volcanoes fed by the subduction of a small (as yet unnamed) plate with the source at the south end of Prince William Sound. They don't have the ash typical of a pyroclastic volcano, and are in fact one of the world's largest volcanic batholiths. A very large earthquakes here in 1964 "fired up" one of the volcanoes, that had been covered by ice for years. The caldera stays filled with warm water year round and it periodically steams. I lived nearby for a few years and watched the earthquakes in Prince William Sound often followed by small steam eruptions of that mountain.

.

**Shannon Bennett** · December 31, 2008, 08:49 PM

Re: Scientists watch unusual Yellowstone quake swarm

Hotspot volcanoes are relatively unique. There are less than 30 in the world and, some of those may be extinct. Many of the others are located under oceans and are of little concern. The reason for the different kinds of threat is due to the kind of rock that lies on top of the hotspot. Lighter continental rock is explosive when it melts, whereas basalts found in oceanic basins is not. The driving mechanism for these kinds of volcanoes is thought to be due to radioactive decay. But, as the heat that partially melts the rock is located between the the two top layers of the earth, we may never know for sure. Subducting plate boundary volcanoes are nearer the earths surface compared to hotspots.

Spreading centers are found usually under the oceans (but not always). Long rifts ooze magma up from below. There are some of these off the Pacific northwest coast. These volcanoes typically do not impact people. Exceptions include Iceland and the African Rift Valley.

Hotspot volcanoes are stationary while continents are mobile. So, when we look at Yellowstone we can see a long valley stretching across Idaho. All along that long valley one Yellowstone volcano after another blew up forming calderas. We still see hot springs along much of its length. An interesting side note is Boise heats some of its downtown from pipes leading from local hot springs. Hawaii is another hotspot. If you look at a topographic map of the Pacific basin you can see a long ine of extinct volcanoes. They at one time were located where Hawaii is today. The plate over millions of years has been shoved northwards leaving the hotspot to create new volcanoes as new plate lies over the top.

**JJackson** · December 31, 2008, 09:56 PM

Re: Scientists watch unusual Yellowstone quake swarm

<meta http-equiv="Content-Type" content="text/html; charset=utf-8"><meta name="ProgId" content="Word.Document"><meta name="Generator" content="Microsoft Word 10"><meta name="Originator" content="Microsoft Word 10"><link rel="File-List" href="file:///D:%5CDOCUME%7E1%5CADMINI%7E1%5CLOCALS%7E1%5CTemp%5 Cmsohtml1%5C01%5Cclip_filelist.xml"><o:smarttagtyp e namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="PlaceName"></o:smarttagtype><o:smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="PlaceType"></o:smarttagtype><o:smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"></o:smarttagtype><style>  </style> We may all be misunderstanding each other but my understanding is this.
<o:p> </o:p>
There are volcanoes on plate boundary subduction zones (Ring of Fire etc.) which form when the water bearing plate is subducted and melts with the new melt rising and forming the magma-chambers and new volcanoes (important in the long term carbon cycle - and you get diamonds which is always nice).
<o:p> </o:p>
The hot spot volcanoes are fixed plumes of small diameter which ?bubble? through the centre of plates holding their position as the plate floats by above. They usually cause chains of ocean islands and seamounts with an active one followed by a string of extinct volcanoes of progressively greater age.
<o:p> </o:p>
<st1:place>Yellowstone</st1:place> is a super volcano which is a hot spot but on an entirely different scale (<st1:place>Yellowstone</st1:place> released about 1000 times as much material as <st1:place><st1:placetype>Mt.</st1:placetype> <st1:placename>St. Helens</st1:placename></st1:place>). Here the rising magma chamber is of such size it melts the crust over a sizeable area (The Deccan Traps released magma for 30,000 years leaving the flats which are 2km thick basalt in places and cover half a million sq. km). The attendant dust cloud and SO2 release do not just make pretty sunsets they cause ice ages. There has not been a super volcano eruption during the Holocene; when one does occur it will be attended by mass extinctions.

**AlaskaDenise** · December 31, 2008, 10:26 PM

Re: Scientists watch unusual Yellowstone quake swarm

I read that the term "hotspot" is one of those new terms to express an old idea - that volcanoes tend to occur in the same place over time. Some sources say there are at least 40-50 hotspots. Sounds like one of those theories that interpretation depends on who you talk to.

However, no matter what it's called, volcanoes do tend to occur in areas of "unstable geology". That's why I don't find it surprising that they can be impacted by earthquakes, sometimes quite distant.

The shield volcanoes in the source (spreading) region of tectonic plates aren't explosive because they're composed of more pure basalts and have comparatively little to no rock over them. See:

The pyroclastic volcanoes that result from subduction are more explosive because the plate carries many years accumulation of organic material deposited on the ocean floor, to beneath the plate being subducted. Those organic materials (including water) create an explosive mixture that releases itself into an unstable geologic area as a pyroclastic, explosive volcano. For a land-based pyroclastic see:

The pyroclastic volcanoes sometimes occur in or near oceans when the area of subduction occurs under the ocean floor (as Krakatoa). See:

So the nature of oceanic volcanoes depends on whether they're in the spreading zone or a subduction zone.

I noticed that one theory for Yellowstone activity is that plate movement "rearranges" the geology of underground areas feeding that magma chamber. I would expect that will be evidenced by earthquakes - some being quite distant.

It will be interesting to watch.

**Shiloh** · January 1, 2009, 07:47 AM

Re: Scientists watch unusual Yellowstone quake swarm

Here's another article on the yellowstone caldera...comments are interesting:

404 | Scientific American

http://www.sciam.com/blog/60-second-science/post.cfm?id=multiple-tiny-earthquakes-rattle-ye-2008-12-30

Scientific American is the essential guide to the most awe-inspiring advances in science and technology, explaining how they change our understanding of the world and shape our lives.

**Shannon Bennett** · January 1, 2009, 12:22 PM

Re: Scientists watch unusual Yellowstone quake swarm

Page not found – Department of Geological Sciences

http://www.geology.sdsu.edu/how_volcanoes_work/intraplvolc_page.html

I nice diagram explaining why a hotspot volcano is different from other kinds of volcanoes.

<CENTER>INTRAPLATE VOLCANISM</CENTER>

<CENTER><HR SIZE=3></CENTER>

HOT SPOTS AND MANTLE PLUMES

Although most volcanic rocks are generated at plate boundaries, there are a few exceptionally active sites of volcanism within the plate interiors. These intraplate regions of voluminous volcanism are called hotspots. Twenty-four selected hotspots are shown on the adjacent map. Most hotspots are thought to be underlain by a large plume of anomalously hot mantle. These mantle plumes appear to be generated in the lower mantle and rise slowly through the mantle by convection. Experimental data suggests that they rise as a plastically deforming mass that has a bulbous plume head fed by a long, narrow plume tail. As the head impinges on the base of the lithosphere, it spreads outward into a mushroom shape. Such plume heads are thought to have diameters between ~500 to ~1000 km.

<CENTER><TABLE cellSpacing=2 cellPadding=0 width=450 border=0><TBODY><TR><TD width="50%">
<CENTER> </CENTER></TD><TD width="50%">Many scientists believe that mantle plumes may be derived from near the core-mantle boundary, as demonstrated in this computer simulation from the Minnesota supercomputing lab. Note the bulbous plume heads, the narrow plume tails, and the flattened plume heads as they impinge on the outer sphere representing the base of the lithosphere.</TD></TR></TBODY></TABLE></CENTER>
Decompressional melting of this hot mantle source can generate huge volumes of basalt magma. It is thought that the massive flood basalt provinces on earth are produced above mantle hotspots. Although most geologists accept the hotspot concept, the number of hotspots worldwide is still a matter of controversy.
HOTSPOT TRACKS

The Pacific plate contains several linear belts of extinct submarine volcanoes, called seamounts, an example of which is the Foundation seamount chain shown here.

<CENTER><TABLE cellSpacing=2 cellPadding=0 width=553 border=0><TBODY><TR><TD width="56%">
<CENTER> </CENTER></TD><TD width="44%">The Foundation seamount chain is located near Easter Island in the south Pacific. Courtesy of NOAA.</TD></TR></TBODY></TABLE></CENTER>
The formation of at least some of these intraplate seamount chains can be attributed to volcanism above a mantle hotspot to form a linear, age-progressive hotspot track. Mantle plumes appear to be largely unaffected by plate motions. As lithospheric plates move across stationary hotspots, volcanism will generate volcanic islands that are active above the mantle plume, but become inactive and progressively older as they move away from the mantle plume in the direction of plate movement. Thus, a linear belt of inactive volcanic islands and seamounts will be produced. A classic example of this mechanism is demonstrated by the Hawaiian and Emperor seamount chains.

<CENTER><TABLE cellSpacing=2 cellPadding=0 width=450 border=0><TBODY><TR><TD width="100%"> <TABLE cellSpacing=2 cellPadding=0 width=450 border=0><TBODY><TR><TD width="48%">
<CENTER> </CENTER></TD><TD width="52%">
<CENTER> </CENTER></TD></TR></TBODY></TABLE></TD></TR><TR><TD width="100%">The image on the left shows the Hawaiian and Emperor seamount chains. The Hawaiian chain begins at the Hawaiian Islands, to the southeast, and continues to the bend located ~5000 km to the northwest. From the bend, the Emperor chain continues to the north-northwest until it terminates at the Aleutian trench (Courtesy of NOAA). The diagram on the right is a model demonstrating how these chains form above the stationary mantle plume, becoming progressively older to the northwest (Courtesy of the USGS).</TD></TR></TBODY></TABLE></CENTER>
The "Big Island" of Hawaii lies above the mantle plume. It is the only island that is currently volcanically active. The seven Hawaiian Islands become progressively older to the northwest. The main phase of volcanism on Oahu ceased about 3 million years ago, and on Kauai about 5 million years ago. This trend continues beyond the Hawaiian Islands, as demonstrated by a string of seamounts (the Hawaiian chain) that becomes progressively older toward Midway Island. Midway is composed of lavas that are ~27 million years old. Northwest of Midway, the volcanic belt bends to the north-northwest to form the Emperor seamount chain. Here, the seamounts become progressively older until they terminate against the Aleutian trench. The oldest of these seamounts near the trench is ~70 million years old. This implies that the mantle plume currently generating basaltic lavas on the Big Island has been in existence for at least 70 million years!
The Hawaiians were very good at recognizing the difference in the older, eroded volcanic islands and newer islands to the southeast, where volcanic features are more pristine. Legend has it that Pele, the Hawaiian goddess of fire, was forced from island to island as she was chased by various gods. Her journey is marked by volcanic eruptions, as she progressed from the island of Kaua'i to her current home on the Big Island. The legend corresponds well with the modern scientific notion of the age progression of these volcanic islands.
Go to:

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**JJackson** · January 1, 2009, 01:03 PM

Re: Scientists watch unusual Yellowstone quake swarm

<o:smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="country-region"></o:smarttagtype><o:smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"></o:smarttagtype> I was having a read at some of the links and the scale of some of these events is impressive. The Siberian Traps produced enough basalt to cover the continental US to a depth of about 250m and if it was evenly distributed over the <st1:country-region><st1:place>UK</st1:place></st1:country-region> I would have to re-think my preps a bit. I would need to stock up on oxygen as the air is a little thin now that my house is 10,000ft higher than <st1:place>Mount Everest</st1:place> and I may need more fuel for heating. I am not sure my heritage seeds are going to be as useful as I thought, anyone know a good place to buy extreemophiles mail order? On the plus side getting landing slots at Heathrow is now much easier as only the Space Shuttle and U2's can get there.

**Science Teacher** · January 1, 2009, 04:05 PM

Re: Scientists watch unusual Yellowstone quake swarm

Today's quakes in Yellowstone:

2.7 2009/01/01 05:51:24 44.548N 110.361W 0.2 60 km (38 mi) ESE of West Yellowstone, MT
2.8 2009/01/01 03:13:51 44.527N 110.353W 2.0 61 km (38 mi) ESE of West Yellowstone, MT
2.6 2009/01/01 03:13:00 44.527N 110.356W 0.0 61 km (38 mi) ESE of West Yellowstone, MT
2.4 2009/01/01 03:12:57 44.325N 110.388W 37.0 68 km (42 mi) ESE of West Yellowstone, MT
1.3 2009/01/01 03:12:32 44.535N 110.365W 0.6 60 km (38 mi) ESE of West Yellowstone, MT
2.3 2009/01/01 03:06:51 44.529N 110.370W 0.5 60 km (37 mi) ESE of West Yellowstone, MT
2.9 2009/01/01 03:02:57 44.530N 110.357W 2.0 61 km (38 mi) ESE of West Yellowstone, MT

From: http://www.seis.utah.edu/recenteqs/Maps/110-45.html

**Shannon Bennett** · January 5, 2009, 12:27 PM

Re: Scientists watch unusual Yellowstone quake swarm

Yellowstone Volcano Observatory | U.S. Geological Survey

http://volcanoes.usgs.gov/yvo/

<CENTER>YELLOWSTONE VOLCANO OBSERVATORY INFORMATION RELEASE
Friday, January 2, 2009 19:30 MST (Saturday, January 3, 2009 02:30 UTC)</CENTER>

YELLOWSTONE VOLCANO (CAVW#1205-01-)
44.43°N 110.67°W, Summit Elevation 9203 ft (2805 m)
Volcano Alert Level: NORMAL
Aviation Color Code: GREEN

Yellowstone Lake Earthquake Swarm Update: 2 January 2008

The University of Utah Seismograph Stations reports that as of 1800 MST on 2 January 2009, seismicity of the ongoing Yellowstone earthquake swarm continues. Over 500 earthquakes, as large as M 3.9, have been recorded by an automated earthquake system since the inception of this unusual earthquake sequence that began Dec. 27, 2008. More than 300 of these events have been reviewed and evaluated by seismic analysts. Depths of the earthquakes range from ~ 1km to around 10 km. We note that the earthquakes extend northward from central Yellowstone Lake for ~10 km toward the Fishing Bridge area, with a migration of recent earthquakes toward the north. Some of the dozen M3+ earthquakes were felt in the Lake, Grant Village and Old Faithful areas. Personnel of the Yellowstone Volcano Observatory continue to evaluate this earthquake sequence and will provide information to the NPS, USGS and the public as it evolves.

This earthquake sequence is the most intense in this area for some years. No damage has been reported within Yellowstone National Park, nor would any be expected from earthquakes of this size. The swarm is in a region of historical earthquake activity and is close to areas of Yellowstone famous hydrothermal activity. Similar earthquake swarms have occurred in the past in Yellowstone without triggering steam explosions or volcanic activity. Nevertheless, there is some potential for hydrothermal explosions and earthquakes may continue or increase in magnitude. There is a much lower potential for related volcanic activity.

The University of Utah operates a seismic network in Yellowstone National Park in conjunction with the National Park Service and the U.S. Geological Survey. These three institutions are partners in the Yellowstone Volcano Observatory. Seismic data from Yellowstone are transmitted to the University in real-time by radio and satellite links from a network of 28 seismographs in the Yellowstone area and are available on the web.

Seismologists continue to monitor and analyze data from this swarm of earthquakes and provide updates to the NPS and USGS and to the public via the following web pages.

Information on U.S. earthquake activity including Yellowstone can be viewed at the U.S. Geological Survey web site: http://earthquake.usgs.gov/eqcenter/recenteqsus/.

Information on earthquakes can also be viewed at the University of Utah
Seismograph Stations web site: http://www.seis.utah.edu/.

Seismographic recordings from Yellowstone seismograph stations can be
viewed online at: http://www.quake.utah.edu/helicorder...one/index.html.

An article on earthquake swarms at Yellowstone is available at the following: http://volcanoes.usgs.gov/yvo/public...apr04swarm.php

Persons who felt any of the earthquakes are encouraged to fill out a survey form on the USGS 'Did You Feel It?' web site: http://earthquake.usgs.gov/eqcenter/dyfi/.

Geologic information, maps, and monitoring information for Yellowstone can be found on the Yellowstone Volcano Observatory web site at:
http://volcanoes.usgs.gov/yvo/.

-----
The Yellowstone Volcano Observatory (YVO) is a partnership of the U.S. Geological Survey (USGS), Yellowstone National Park, and University of Utah to strengthen the long-term monitoring of volcanic and earthquake unrest in the Yellowstone National Park region. Yellowstone is the site of the largest and most diverse collection of natural thermal features in the world and the first National Park. YVO is one of the five USGS Volcano Observatories that monitor volcanoes within the United States for science and public safety.

**mordan** · January 9, 2009, 02:21 PM

Re: Scientists watch unusual Yellowstone quake swarm

Yellowstone Seismogram Thumbnails - Thursday, 4/18/2024

http://www.isthisthingon.org/Yellowstone/daythumbs.php

At it again.

**AlaskaDenise** · January 9, 2009, 05:33 PM

Re: Scientists watch unusual Yellowstone quake swarm

Mordon - thanks for the graph links.

Those don't show up on the USA latest earthquakes of >1 on the Richter scale list, as of 6 minutes ago. I'd love to see a more distant graph to see the waves from a different angle. Some may be small harmonic tremors, since I cannot distinguish an "S" wave, however, the sensitivity is turned way up (as evidenced by the larger ones being cut off), so some "S" waves may not be obvious. The "S" wave wouldn't show up if the Seismograph is close to the quake, but it should show up at more distant sites. But at least they don't have the signature of a prolonged harmonic tremor (major magma movement).

There are so many earthquakes is geologically active areas of Western areas of the US right now - see those in "the Geyers" of the California Coast Range - north of SF.

.

**Shiloh** · February 2, 2009, 03:23 PM

Re: Scientists watch unusual Yellowstone quake swarm

Source: http://www.denverpost.com/news/ci_11610449

Earthquake swarm was 2nd-largest for Yellowstone
By Howard Pankratz
The Denver Post
Posted: 02/02/2009 11:52:21 AM MST
Updated: 02/02/2009 11:57:52 AM MST

The swarm of earthquakes that hit Yellowstone National Park in late December and January was the second-largest earthquake swarm in Yellowstone's recorded seismic history, the Yellowstone Volcano Laboratory said today in its updated analysis of the earthquakes.

more....

Howard Pankratz: 303-954-1939 or hpankratz@denverpost.com

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Scientists watch unusual Yellowstone quake swarm

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