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How deep is the Connecticut River? Would it surprise you to know
that in some places its depth exceeds 125 feet? It surprised me.
Two deep sites in Massachusetts are currently being explored by
divers. The following map shows their locations; both are near
where the French King Bridge spans the Connecticut River. Site B, known as
French King Hole, has been dived for years by Valley Divers . The second site, labelled Site A, known as
King Philip's Abyss, was recently (summer, 1997) discovered and
explored by University of Massachusetts divers. Both sites
should be dived with caution: they are very deep, totally without
light (dark as the inside of a cow!), have overhangs, and there
is the possibility of entanglement from waterlogged, uprooted
trees (roots, trunk and crown) that sink to the bottom.
As you will note on the map, both of these deep sites are close
to a fault that crosses the Connecticut River. This fault, known
as the Border Fault, is worth a geological digression.
Approximately 200 million years ago, all of the continents were
united into a single supercontinent called
Pangea. Subsequently faults separated the continental plates
and they began the slow drift to their present locations. During
the initial phase of this continental break up, a fault (the
Border Fault) developed through what is now the Connecticut River
Valley. This fault aborted, and another occurred east of Boston
separating North America from Africa. Had the Border Fault not
aborted, Boston would be in Africa and Greenfield, Massachusetts
would be a coastal resort! Too Bad.
French King Hole (Site B) exactly coincides with where the Border Fault
crosses the river.
THE BORDER FAULT CROSSES THE RIVER IN THE FOREGROUND
UPSTREAM FROM THE FRENCH KING BRIDGE. THE BORDER FAULT IS ON THE RIGHT (EASTERLY) SIDE OF THE RIVER
Faulting may result in neighboring rocks either becoming stronger
or weaker. According to Professor Little, a geologist at
Greenfield Community College, the rocks in the French King Gorge have been weakened by the
Border Fault. Perhaps the 125' depth of this sector of the river
is due to the erosion of these fault-weakened rocks by great
volumes of water that have flowed through the Gorge in the
King Philip's Abyss is near the Border Fault, but no known fault
crosses the river at this location. The origin of the Abyss is
geologically unresolved, but its proximity to the Border Fault is
DIVE FLAG MARKS THE ABYSS
Of the two deep (125 feet plus) river sites, King Philip's Abyss
is the more interesting biologically. Therefore our discussion
will focus on this habitat. The Abyss is an underwater cliff
that crosses the river. The edge of the cliff is 20-30 feet
beneath the surface and plunges almost straight down for 80 feet
in some locations. The
bottom of the cliff is abrupt and then begins an unexplored slope
of gravel and boulders going deeper. In some places the cliff is
undercut into cavern-like areas.
Since the cliff is in the lee of the flow of the river, this
habitat is unique. The cliff wall is festooned with life: white
sponges as big as dinner plates and colonies of the
bryozoan, Lophopodella carteri, a state listed species, cover the cliff face between the sponges.
SPONGES GROWING ON ABYSSAL WALL. NOTE DIVER'S ARM FOR SCALE.
AND MORE SPONGES!
We as yet know very little about this deep water cliff-face
community of invertebrates. During any given dive, because of the depths, only 10-15 minutes
are spent sampling for organisms; thus the total diving time actually spent
studying this unique environment has probably been less than one
We really don't know what is
living down there! This might be the last environment in
Massachusetts whose biota is unknown.
Hamblin, W. Kenneth. 1985. The Earth's Dynamic Systems,
4th Edition. Macmillan Publishing Company, New York. See Chapter 22 for a clear discussion of continental drift.
Stopen, Lynne E. 1988. Geometry and deformation history of
mylonitic rocks and silicified zones along the Mesozoic
Connecticut Valley border fault, western Massachusetts. Master's
Thesis, Department of Geology and Geography, University of