Welcome.Alan.
Back in the early 80's I used to be the area geophysicist for the East Coast
of the US. As such I looked at lots of seismic data along the entire East
coast. Clathrates are seen on seismic as a bottom mimicking strong
amplitude reflector. They are quite widespread in the deeper parts of the
East coast. Surprisingly we don't see them often in the gulf of Mexico. I
don't know why.We knew about these things, they were a drilling hazard for
us If you drill through them and lots of gas is liberated, it can be
disastrous. If a large bubble of gas comes up under a drillship, it will
lose its bouyancy. Stated simply, a boat can't float in air. I have heard
tales of tugboats being swallowed by a gas bubble, only to bob to the
surface with a bruised and scared crew. They were saved by having been
tightly closed up. Other ships have been lost due to that sort of thing. I
am required to examine seismic data prior to drilling a well so that we can
avoid things like that.
glenn
Foundation, Fall and Flood
http://www.isource.net/~grmorton/dmd.htm