Hello-

I'm not a volcanologist, but I'll pass this along to one of the volcanologists in the next building. Thank you for your interest.

Greg Durocher
gfdurocher@usgs.gov

Transaction=GSFXPHKT [28OCT2004 04:09:48UTC]
Customer email: Goldeneagle5@adelphia.net
Customer: Martin Thurman Sr.
Subject: Mount Saint Helens New LAVA DOME - South Creep

Your inquiry has been forwarded to the USGS Cascades Volcano Observatory

for response. You may visit their web site at http://vulcan.wr.usgs.gov/ .

Cheryl O'Brien

USGS

I'm not sure I fully understand the question, but some comments follow:
Domes have not grown exclusively in the same site over the past 4500 years. For example, the Goat Rocks dome, which was swept away by the May 18, 1980, landslide, grew on the north flank; the Sugar Bowl and Dogs Head domes are preserved along the north rim of the crater. Several other domes that formed from eruptions within the past 4500 years exist in other places on the outer flanks of the volcano. Thus, there is nothing exclusive about the site of the 1980-86 dome.
The feeder for the current eruption reaches the ground surface (or glacier surface) immediately south of the 1980-86 lava dome. It may well be that the 1980-86 dome and/or its feeder have deflected the feeder for the new dome slightly southward.
The new dome is growing southward, but that does not imply it that is now intruding or at some future time will intrude or disrupt the south flank of the volcano. A dome's geometry is controlled by gravity and the viscosity of the lava. Accordingly, the new lava spreads, driven by gravity, laterally or down hill. If it grows large enough, it will bank against the crater walls; it is not expected to mow them down. If dome growth continues long enough, the dome could eventually fill the crater, after which avalanches from the dome could spill down the current outer flanks of the volcano. Unitl then, the crater wall blocks its southward growth just as the 1980-86 lava dome is currently blocking its northward growth.
The best available evidence, which comes from earthquake locations, strongly indicates that the magma -supply system (conduit and mid-crustal reservoir) are located vertically beneath the 1980-86 dome and crater floor. The is no efvidence to suggest that the present feeder system is slanted downward to the south-southeast.
There is simply no evidence to support the concept that a lava dome growing in the crater will penetrate the south crater wall and erupt southward.


Edward W. Wolfe
Scientist Emeritus
U.S. Geological Survey
2725 Boone Court
Prescott, AZ 86305
928-776-4754
ewwolfe@usgs.gov

Ed,

Could you please respond to this inquiry? You may want to consult with DZ and JP or others.

Thank you.

Carolyn

Carolyn L. Driedger
Hydrologist

*************
US GEOLOGICAL SURVEY
CASCADES VOLCANO OBSERVATORY
BUILDING 10 SUITE 100
1300 SE CARDINAL COURT
VANCOUVER, WA 98683

(360) 993-8907

Check out our website: http://vulcan.wr.usgs.gov

----- Forwarded by Carolyn L Driedger/WRD/USGS/DOI on 10/28/2004 08:45 AM -----

Your inquiry has been forwarded to the USGS Cascades Volcano Observatory for response. You may visit their web site at http://vulcan.wr.usgs.gov/ .

Cheryl O'Brien
USGS

Martin Thurman Sr. writes
MSH New Lava Dome

Date: October 23, 2004 at 02:42:23

I still believe MSH new lava dome is creeping south. By pictures and closer viewing since the last time I posted the Dome has moved backward to the SSE almost to the crater wall now. The dome may intrude into the south wall. And I also believe the Magma chamber is actually on a slant from the SSE thrusting the Old magma to the NNW giving the false security that it is thrusting straight up. If it penetrates the South wall there is a possibility is can also Erupt to the South side IF the new DOME plugs up and cools to fast from Glacier ice. The Steam I see would warrant this phenomenon.


Date: October 27, 2004 at 16:57:41

If I may make a small comment. I keep thinking that the new dome is doing the same as 1980, but in a different way.

1# The dome is still ejecting new hardened lava "from the old Magma plug" Massive pressure with a lubricated chamber allows for little or no seismic activity without restriction.

#2The new Dome is now Creeping to the South wall of the crater because it "can not" Form in its normal direction the way it has for the last 4500 years. The lateral blast destroyed the mountain built from the entire previous dome building periods. Because I think the Magma Chamber is in a 60 to 70 degree angle. "Not a vertical magma conduit". It is pushing against the post OLD 1980 built dome causing a blockage as it was in the past build periods to the North. This is why it is moving to the south without restriction because it is in a layered section of old dome built material made over hundreds of years (The weakest link). This is why there is lack of larger earthquakes within the dome.

#3 IMO if the dome building process "does not" subside I believe there will be a new Lateral South wall explosion then vertical blast Ash Column! Again the South wall is now the weakest point in the crater.

Oct 31, 2004

Dear Edward W Wolfe,

Sir,

I disagree somewhat with your findings in regard to the South creep.

For the record:

#1 In the amount the New lava dome is growing and expaning to the south.

#2 Why is the USGS for some reason is NOT showing pictures from the SSE side of the new dome (Taken looking to the NNW).

#3 The magma and venting is also moving South WITH the direction of the new dome! If the original ash eruption had continued in the same place, I would agree with your analogy. But it continues to move South with the Dome expansion. Clarified: The new magma is moving south of the original site where MSH first erupted Oct 1, 2004

#4 The Original thrust of the open conduit is now Plugged and allowing the magma the move freely to the surface, again in a southerly direction. Using the OLD 1980 Dome growth as a THRUST BLOCK! With this in mind I would ask you to further look into this matter. There are many lives at risk on the southern flanks of MSH.

Sincerely,

Martin Thurman

Goldeneagle5@adelphia.net