One Big, Happy Family
For the previous
hundred plus million years, North America and Africa had been on a slow
collision course. Finally, in the Permian Period
[PURR-me-in] , the two continents are butted up against each other.
In the process, an ocean was closed up, intervening islands,
ocean floor sediments and smaller continental plates were pasted on to
North America and a mountain range that probably rivalled today's
Himalayas were built.
What was going on
in the rest of the world at this time? At the same time that the
North American and African plates were on the move, so were all
the other plates. The fascinating aspect of all these plates on
the move was that they were all heading into each other to create one
giant land mass, called Pangea [pan-JEE-uh].
It's All Greek To Us
Pangea comes from two Greek words:
pan - meaning "all
gea- meaning "Earth"
Therefore, Pangea translates into 'all one Earth'. To
see if this makes sense, take a look at the map at right.
How do we know that
all of the land masses were together? We don't know for sure,
because human beings weren't around yet to witness this. Harking
back to the discussion in the Precambrian Period about
theories; the nature of a theory is that it is an educated guess to
explain something that is backed up by pieces of evidence.
The evidence in this case is
found in the rocks. There are rock types and rock layers that are
identical in Boston Harbor and North Africa, and in several other
locations around the world that were next to each other. There
are similar fossils found in
the rocks of continents that are now far apart from each other located
in different climates from each other. There are similar plant
and animal types found in continents that are now far apart. For
example, have you ever noticed the similarities between a jaguar from
South America and a leopard from Africa?
Permian Rocks In New Hampshire
The only Permian rocks created
in New Hampshire are the same two-mica granites that started to form in
the Carboniferous Period found near Conway and the Ossipee area
as well as along the Mid-Massachusetts border area.
The Great Permian Extinction
Throught the course of Earth's
history, there have been sudden mass extinctions
of plants and animals as observed in the fossil record. Several
of these mass extiction episodes mark the boundaries of the geologic
time periods. Scientists have their theories, but no definite
answers yet. (See box at right.)
Whatever it was that caused the mass extinction
that marked the end of the Permian Period, it
was the most drastic extinction that ever occured. Life on Earth
was at its closest to ever being wiped out since it began. More
than 90% of all plant and animal species were wiped out. This
cleared the way for the reptiles to have their turn to dominate animal
life on Earth for the next tens of millions of years. That is
until they were wiped out in their own mass extinction episode, which
left the door open for mammals to develop as the dominant animal type.
|Reading The Rocks
Just as you can
see the layers found in these rocks at Wallis Sands State Park (tipped
up on their sides from continental collision), geologists have compared
rock layers found on other continents and found
similarities in rock types and layers. Some of those rock types
contain plant fossils that are identical on South America, Africa,
Australia, India and Antarctica. Since the seeds are too heavy to
have blown across oceans, and these continents have very different
climates today, scientists believe they must have been connected to
each other at one time and shared a similar climate where this plant
could have grown.
(Click on the image for a closer look.)|
credit: Daniel E. Reidy
credit: Daniel E. Reidy
granite usually forms with one kind of mica embedded in it. (See
"The Recipe For Granite" box in the Silurian Period page.) What
is special about the granite that formed during the Carboniferous and
Permian Periods is that it contained two kinds of mica. Here is
what two mica granite looks like (from the Conway area):