America's Volcanic Past
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"Though few people in the United States may actually experience an erupting volcano, the evidence for earlier volcanism is preserved in many rocks of North America. Features seen in volcanic rocks only hours old are also present in ancient volcanic rocks, both at the surface and buried beneath younger deposits." -- Excerpt from: Brantley, 1994 |
Volcanic Highlights and Features:
[NOTE: This list is just a sample of various New Hampshire features or events and is by no means inclusive. All information presented here was gathered from other online websites and each excerpt is attributed back to the original source. Please use those sources in referencing any information on this webpage, and please visit those websites for more information on the Geology of New Hampshire.] |
Volcanic rocks, not abundant in the state,
are only found associated with the
granitic rocks of the
southern White Mountains.
About 50 percent of the state is underlain by
metamorphic rocks
which are in part derived from the
recrystallization of rocks which were of volcanic origin.
The remainder
of the rocks of the state are granitic or related rocks
Excerpt from: Gold in New Hampshire, 1993, Environmental Fact Sheet CO-1, New Hampshire Department of Environmental Services Website, 2001 |
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The Appalachians:
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Precambrian (greater than 450 million years ago):2
Cambrian:2
Ordovician (500 - 440 million years ago):2
Ordovician:1
Silurian (440 - 410 million years ago):2
Silurian (approximately 430 million years ago):2
Devonian (410 - 360 million years ago):2
Devonian (approximately 400 million years ago):2
Carboniferous-Permian (360 - 245 million years ago):2
Triassic-Cretaceous (345 - 150 million years ago):2
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New Hampshire's Volcanic Rocks |
The Granite State:2
Granite
is the official state rock of New Hampshire.
Granite is the traditional rock in New Hampshire. It gave New Hampshire it's
Nickname of "The Granite State." New Hampshire once had a large industry
surrounding the quarrying of granite.
Beryl is the official state mineral of New Hampshire.
Beryl is a gemstone commonly found in the granite rocks abundant in the state. Beryl
Crystals are a yellow-green and yellow colors.
Smoky quartz is the official state gem of New Hampshire.
Smoky Quartz is a common mineral also found in many types of rocks, including
granite. It is also know as cairngorm.
New Hampshire's Volcanic Rocks:1
Volcanic rocks, not abundant in the state,
are only found associated with the
granitic rocks of the
southern White Mountains.
About 50 percent of the state is underlain by
metamorphic rocks
which are in part derived from
the recrystallization of rocks which were of volcanic origin.
The remainder
of the rocks of the state are
granitic or related rocks.
(See more White Mountains below)
New Hampshire's Gold |
New Hampshire's Gold:1
Gold, in anomalous amounts,
is not only associated with granitic rocks, but also with rocks
such as serpentinite at the
other end of the igneous spectrum.
Gold is commonly associated with
volcanic rocks,
especially those characterized by the
analogs of granitic rocks, rhyolite for example.
Flume Gorge State Park |
Flume Gorge:6
Nearly 200 million years ago in Jurassic times,
the Conway granite that forms
the walls of the Flume was deeply
buried molten rock.
As it cooled the granite
was broken by closely spaced vertical
fractures which lay nearly parallel in a
northeasterly direction. Sometime
after the fractures were formed, small dikes
of basalt were forced up along the
fractures. The basalt came from deep
within the earth as a fluid material,
and because of pressure, was able to force
the Conway granite aside. The basalt
crystallized quickly against the relatively
cold granite. Because of this quick
cooling, the basalt is a fine grained rock.
Had this material ever reached the surface,
it would have become lava flows.
Erosion quickly lowered the earth's
surface and exposed the dikes. As the
overlying rock was worn away,
pressure was relieved and horizontal cracks
developed which allowed water to get
into the rock layers. The basalt dikes
eroded faster than the surrounding
Conway granite, creating a deepening
valley where the gorge is now.
The gorge was covered by glaciers
during the Ice Age, but the ice sheet did
not greatly change the surface.
It partially filled the valley with glacial debris
and removed soil and weathered
rock from the vicinity. After the Ice Age,
Flume Brook began to flow through the valley again.
The highly fractured granite and
basalt have been eroded by frost action as
well as by the brook's water.
As you walk through the Flume, you may see
remnants of the main basalt dike
on the floor of the gorge and small branches
along the canyon walls. The process
of erosion is still occurring in the Flume.
Franconia Notch State Park |
Old Man of the Mountain:6
The Old Man of the Mountain, nicknamed the Great
Stone Face or Profile (immortalized by
Nathaniel Hawthorne and Daniel Webster), is located in Franconia Notch
State Park. The Old Man of the Mountain is scenically
set 1,200' above Profile Lake.
The Profile is a natural rock formation that was formed
by a series of geologic happenings that began an
estimated 200 million years ago. Hovering majestically
1,200 feet above Profile Lake,
the Old Man is made of
five separate granite ledges arranged horizontally to form
a man's profile.
From chin to forehead, the Profile
measures about 40 feet and is 25 feet wide.
The Old Man of the Mountain is the State Symbol for
New Hampshire and was chosen as representation for
the New Hampshire Quarter.
Mt. Kearsarge |
Mt. Kearsarge:6
Located in Warner and Wilmot, New Hampshire, 2,937-foot Mt. Kearsarge,
one of the oldest mountains in the state, is the home of both Winslow and
Rollins state parks. Because of its easy accessibility from the parks and
outstanding summit vistas, Mt. Kearsarge is a popular family hiking
destination. Views include nearby Sunapee, Ragged and Cardigan mountains
and more distant Mt. Monadnock and Ascutney. On very clear days views
extend to the White Mountains,
the Green Mountains of Vermont, the Atlantic
Ocean and Boston.
The exposed granite summit
is a good
place to see evidence of past glacial
activity. During the glacial period
more than 25,000 years ago, a great ice sheet
more than a mile thick moved over
Kearsarge and much of New Hampshire.
Glacial striations, grooves cut in
rock by the movement of glacial ice, can be
seen on the summit, as well as on
ledge outcroppings in the Winslow picnic
area. In addition, large boulders
called glacial erratics, can be seen from the
trails. The mass of ice was powerful
enough to move the boulders which were
left behind when the ice sheet retreated.
The bare summit is the result of a
1796 forest fire which burned the
vegetation and exposed the soil to wind and
water erosion.
Old Man of the Mountain |
Old Man of the Mountain:6
The Old Man of the Mountain, nicknamed the Great
Stone Face or Profile (immortalized by
Nathaniel Hawthorne and Daniel Webster), is located in Franconia Notch
State Park. The Old Man of the Mountain is scenically
set 1,200' above Profile Lake.
The Profile is a natural rock formation that was formed
by a series of geologic happenings that began an
estimated 200 million years ago. Hovering majestically
1,200 feet above Profile Lake,
the Old Man is made of
five separate granite ledges arranged horizontally to form
a man's profile.
From chin to forehead, the Profile
measures about 40 feet and is 25 feet wide.
The Old Man of the Mountain is the State Symbol for
New Hampshire and was chosen as representation for
the New Hampshire Quarter.
Rollins State Park |
Rollins State Park:6
Located in Warner and Wilmot, New Hampshire, 2,937-foot
Mt. Kearsarge,
one of the oldest mountains in the state,
is the home of both Winslow and
Rollins state parks.
The exposed granite summit is a good
place to see evidence of past glacial
activity.
[See Mt. Kearsarge above]
White Mountains |
White Mountain's Volcanic Rocks:1
Volcanic rocks, not abundant in the state,
are only found associated with the
granitic rocks of the
southern White Mountains.
About 50 percent of the state is underlain by
metamorphic rocks
which are in part derived from
the recrystallization of rocks which were of volcanic origin.
The remainder
of the rocks of the state are
granitic or related rocks
White Mountains of New Hampshire:3
Many of the rocks in these areas were formed by
eruptions or by intrusion of magma
into the Earth's crust many millions of years ago.
More White Mountains:4
The White Mountain igneous province consists of plutons,
ring complexes, and volcanics
emplaced along a NNE trend across New England.
Four petrographic associations are recognized:
(1) alkali syenite-quartz syenite-granite;
(2) subaluminous biotite granite;
(3) gabbro-diorite-monzonite and;
(4) syenite-nepheline syenite.
The igneous activity is largely confined to two periods,
200-165 million years ago and 130-110 million years ago.
These two major periods of igneous activity
are related to the
opening of the North Atlantic Ocean.
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Winslow State Park |
Winslow State Park:6
Located in Warner and Wilmot, New Hampshire, 2,937-foot Mt. Kearsarge,
one of the oldest mountains in the state, is the home of both Winslow and
Rollins state parks.
The exposed granite summit is a good
place to see evidence of past glacial
activity.
[See Mt. Kearsarge above]
Excerpts from:
1) Gold in New Hampshire, 1993, Environmental Fact Sheet CO-1, New Hampshire Department of Environmental
Services Website, July 2001
2) New Hampshire Department of Environmental
Services Website, July 2001
3) Brantley, 1994,
Volcanoes of the United States:
USGS General Interest Publication
4) Creasy and Fitzgerald,
Bedrock Geology of the Eastern White Mountain Batholith,
North Conway Area, New Hampshire
5) USGS/NPS Geology in the Parks Website, August 2001
6) New Hampshire State Parks Website, 2002
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