New Hampshire Geology New Hampshire Bedrock Map

Triassic Period
(245-206 million years ago)

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.

Splitting Up

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.

odiorne dike

Here is a smaller dike running through the rocks at Odiorne Point.  The pocket knife is for scale.

              little dike

(Click on the image for a closer look.)|
Image credit: Dan Reidy


A View That Shouldn't Be

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