Mysa or Syra (whey); Subglacial Volcanism Definitions

James A. Landau JJJRLandau at AOL.COM
Tue Jul 17 16:40:46 UTC 2001

In a message dated 7/17/01 11:57:02 AM Eastern Daylight Time,  His Honor
Bapopik at AOL.COM writes:

>   OED also doesn't have "shield glaciers," or ice-cap glaciers resting on a
> single mountain.  OED does have "shield volcanoes."
>     Table mountains, _stapar_ such as Hrutfell, or tuff were formed in
> eruptions under glacial caps.  The shield volcano, or _dyngja_; Kjalhraun
> formed by thinly flowing lava soon after the glaciers receded.

I think you are confusing two very different geologists' meanings of "shield".

A "shield volcano" is one formed by flows of very fluid lava.  The Hawaiian
islands are shield volcanoes.  The other extreme is a "cinder cone" formed
from solid pieces of volcanic rock (e.g. the "tuff" cited above, the idea is
"volcanic cinders").  A good example is Paracutin in Mexico.

As long as they're dormant, a shield volcano and a cinder cone can have very
similar glaciers.

"ice-cap glacier" is an ambiguous term.

There are two kinds of glaciers.  One is called I think (I don't have a
geology text handy) a "mountain glacier" or "valley glacier".  This is the
type of glacier that in the right climate would form on either a shield or a
cinder cone volcano.

The other type is a "continental glacier" (again, check a geology text).
This is a mass of ice of continental scope that covers both plains and
mountain ranges with  icy indifference.  Greenland is covered by such a
continental glacier.  It may be that "shield glacier" is a synonym for
"continental glacier".

        - Jim Landau

P.S. Your Honor, the controversy over Bush's nominee for Solicitior General
has brought to my mind the question: why is the office called "Solicitor
General" when in fact the occupant is the Barrister General of the US

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