Date:         Fri, 27 Oct 1995 05:00:16 MST
From: Gerard Fryer 
Subject:      Northern Marianas

A seamount 25 miles northwest of Saipan is currently erupting.
Two weeks ago fishermen saw discolored water. Personnel of the
CNMI (Commonwealth of the Northern Mariana Islands) Wildlife and
Emergency Management Office (EMO) surveyed the site and measured
a bottom depth of 200 m. More recently fishermen reported
"explosions" (though nothing broke surface). EMO went back on
October 25, confirmed the submarine explosions, and measured a
bottom depth of 60 m. It isn't clear what navigation equipment
was used so we cannot really conclude yet that the seamount grew
150 m.

Activity continues. CNMI has issued a tsunami alert, not because
a major catastrophic eruption is expected, but because near
surface activity could build a very unstable structure which
might collapse, generating waves which would threaten the nearby
islands of Saipan, Rota, and Tinian. Residents have been advised
to be ready to evacuate low-lying areas on short notice or
immediately on feeling any ground tremors (the tsunami travel
time would be about fifteen minutes).

The Northern Marianas are predominantly basalt and andesite,
though the breached cone of Maug Island has a submarine
dome (Maug looks like it erupted very much like Mt. St.
Helens).  Basaltic activity has occured within the last fifteen
years at the island of Pagan and on the seamount Esmeralda
Gerard Fryer
Hawaii Inst. of Geophysics & Planetology