"The 1980 blast obliterated the top 1,300 feet of the volcano"
The difference between the elevation of the old summit
and the elevation of the crater floor is a lot greater
than 1,300 feet. The mountain's highest elevation happens
to be 1,300' lower, but the 1980 blast blew away quite
a lot of the mountain.
A lot of these articles are pretty poorly written, imho.
They should really say, that half (or whatever the number
is) the mountain was blown away in 1980.
Wouldn't it be something if in ten years Mount Saint Helens
was the tallest mountain in Western Washington? Nobody
makes outrageous predictions like this, but outlier
forecasts can be right, however infrequently. Probably
Cascade volcanos are explosive, and rebuild only very
slowly--but I remember as a kid hearing about a new
volcano that was born in a Mexican corn field, and
became quite massive in just years to decades.
Ah, here is the Helens FAQ!
wrgis.wr.usgs.gov
The images suggest something less than half
was blown away, but this is good: If 1300'
of the summit is gone, plus the crater is
2100' deep, that suggests to me that a good
3400' of mountain was blown away from old
summit to crater floor.
The Faq has the volume stats too.
The 500M tons of ash seems like an awful
lot, I'd like to convert that to volume
and compare that to the volume of the
mountain that is gone--how much magma came
up out of the earth? Sounds like a lot.
Maybe it will indeed take a long time to
replace that much magma...and replace the
mountain.
Still, for fun, I am going to make the wacky
prediction that Helens completely rebuilds in
my lifetime...plus some. Why not?
Now to find out the difference between basalt
and dacite again. Geology 101 is quite a lot
of fun, crystals and chemistry and stuff. |
