Vibe-Fall-2024 - Flipbook - Page 63
IN OUR MIDST
surmise, the Ossipees, and other nearby
mountains are not extinct or dormant
volcanoes. Volcanic cones tend to erode
rather quickly, geologically speaking, and
the original volcanoes that covered our
area are long gone. Out west, where the
rocks are much younger in places, one
can still see ancient volcanic cones or the
remains of underground “plugs” that fed
magma to the surface. The Devil’s Tower in
Wyoming is one such famous example.
The ridgeline of the Ossipee Mountains forms a circle with lowlands in the
middle, the donut hole of this perfect
ring. The circular nature of the range
escapes the eyes of most because it can’t
be seen from ground level or even from
most nearby mountains. But take a look
at topographic maps or aerial photos, and
there it is—a mountain range in the shape
of a ring. A great perspective can also be
had from the summit of Bayle Mountain,
which sits in the middle of the ring dike
and allows the observer to perceive the
ring of surrounding mountains.
Ring dikes have volcanic origins. The
current theory is that magma from deep
within a volcano or magmatic hotspot
Fall 2024
wells up through the earth’s crust, creating
a dome-like area of bedrock that extends
up toward the surface. Magma near the
surface in massive amounts causes the
bedrock surface to lose density and rise.
In present times, the elevated plateau-like
surface of Yellowstone National Park is a
current example of how magma in the
upper parts of the crust can create doming
at the surface. Yellowstone is a high-elevation plateau today, with evidence that, in
the past, it erupted as the crust collapsed
into the voided magma chamber, creating
a volcanic basin. Some of this area of Yellowstone is referred to as the geyser basin,
full of famous sights such as Old Faithful.
Back to ring dikes … at the lower
levels of the crust, as more and more rock
was melted away and eruptions emptied
out magma chambers, the crust above
collapsed at the surface into a caldera,
creating bedrock fractures or “shear faults”
in the process. The magma seeped around
giant circular areas of the melting crust
through these fractures and eventually
solidified into different types of granites,
ash flow deposits, and the syenite magmas
that form the circular-shaped dikes. The
Many hikes throughout the Lakes Region
and White Mountains offer a view of the
Ossipee ring dike. This particular view can
be seen from the Freedom area, especially
with a zoom lens on your camera or binoculars. Photo by WiseguyCreative.com. An
additional view from further away can be
seen on page 24.
The circular nature of the
range escapes the eyes of
most because it can’t be
seen from ground level or
even from most nearby
mountains. But take a look
at topographic maps or
aerial photos, and there it
is—a mountain range in
the shape of a ring.
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