Breaking Up Is Hard To Do
During the Triassic Period
[try-AA-sick], the North American Continent started to pull away, or rift, from the
African and European plates. What may seem like an immediate turn
around after the continents just got together in the preceeding Permian Period, is
anything but. True, it took over a hundred million years for the
North American plate to collide with the African and European plates.
However, you need to keep in mind both the Permian and Triassic Periods
lasted tens of millions of years each. As a result, Pangea was
together for almost a hundred million years itself, before it started
to break up. Some of the signs of the early split-up show up very
nicely at Odiorne Point State Park on the rocky shore. See the
box at right for more.
The lower Connecticut River Valley in Massachusetts and Connecticut is
a much larger example of a Triassic rift Basin in New
England.
Rifting is going
on today in East Africa. Look at a map or globe of Africa and
locate
Lake Malawi and Lake Tanganyika. They are lakes that have filled
in
the rift valley. They will continue to widen and lengthen as the
rift does the same. Interestingly, the oldest hominid (human) fossils
have been discovered in this area as weathering and erosion are
exposing the fossils.
The Wearing Down Of A Continent
Once the building
up of
the North American Continent's massive early Appalachian Mountain chain
ceased
in the Permian Period,
there began the one most significant event that
has shaped our present landscape: the weatheirng and weathering and erosion of about
180 million years.
Weathering and erosion is always
going on.
But when it is coupled with mountain building, the mountain
building
wins out and the land rises. However, in the absence of uplifting
events, weathering and erosion will
eventually wear everything down, especially when given many millions
of years.
Mountains Of Mystery
Geologists
are a bit puzzled at the
existence of our mountains in New Hampshire and along the entire
Appalachian chain. Based on their calculations of weathering and
erosion rates, there should be little or no mountains left. Never
mind that we have mountains over a mile tall still. They have a
couple of choices to consider in order to solve this mystery:
1 There is
still some mechanism of uplift at
work that has yet to be identified; or
2 Their
calculations of the weathering and
erosion process are dead wrong.
Neither scenario is a comforting
one for geologists, because one of their basic underlying
understandings is either unknown still, or in error.
My, What Big Teeth You Have
The Triassic Period is
the
time in Earth's History when the dinosaurs made their appearance.
To
this day, they are the largest land animals that ever existed on Earth.
Sometimes, most of what is known about a dinosaur is learned from
their fossilized teeth found in sedimentary rocks.
(Unfortunately
no sedimentary rocks exist in New Hampshire, so no dinosaur fossils.
See
the Devonian Period
page for information on the few greatly distorted fossils that can be
found in the Granite State.) The dinosaurs developed specialized
teeth for tearing,
crunching and chewing. Depending on what kind of teeth they had,
would
determine whether they were large plant eaters (herbivores), meat
eaters
(carnivores) or everything eaters (omnivores).
Though we don't have any fossil
evidence of dinosuars having lived in New Hampshire, most paleontologists
(scientists who study fossils) and geologists believe
that
they did live here. They believe this because during the Triassic Period,
New Hampshire had a tropical climate - perfect conditions for
the dinosaurs.
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| Splitting Up |
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Evidence of the Earth splitting apart, or rifting, is right here in New
Hampshire! Located at Odiorne Point State Park's rocky shore are
stripes of black basaltic rock running through the lighter colored
rock. The basalt is a
volcanic rock that seeped into cracks formed as the North American and
African Plates started to drift apart in the Triassic Period.
The basalt weathers
easier than the older metamorphic rock that surrounds it.
This explains why the basalt rock
surface is lower than the rock on either side of it, forming a mini
canyon.
Here is a smaller dike
running through the rocks at Odiorne Point. The pocket knife is
for scale.
(Click on the image for a closer look.)|
Image
credit: Dan Reidy
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| A View
That Shouldn't Be |
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This view of
Mts. Jefferson, Adams, Quincy Adams and Madison from the summit of Mt.
Washington shouldn't be there according to what some geologists
calculated. With about 180 million years of weathering and
erosion, they reason, these and all mountains in the Appalachians
should have been worn down to flat plains.
(Click on the image for a closer look.)|
Image
credit: Dan Reidy
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