Download Making of North America Part 2 1. After Rodinia broke apart, North

Making of North America Part 2
1. After Rodinia broke apart, North America had a stable core but the east and west edges were unfinished, and
that would take hundreds of millions of years. Professor Johnson first takes us east to New York to first look
for relics of this continental makeover in Manhattan. Between the apartments he finds a big rock. All over
the city you can see __________________ of bedrock. This bedrock is called the Manhattan Schist.
Buildings built in Manhattan must be anchored deep into the schist, and it is very hard rock to hammer into.
The interesting thing is that the schist started its life as _______________. The rock now as a shiny flakes of
________________ mica crystals. These crystals form at over ____________ degrees. What happened is
that about half a billion years ago a chain of __________________ islands headed toward North America.
These islands bulldozed mud from the sea floor up onto the East Coast and buried it. The mud in time was
transformed into schist. Only where the Manhattan Schist is near the surface can they build the huge
skyscrapers.
2. While today New York’s skyline is dominated by skyscrapers, ____________ million years ago the
skyscrapers would have been dwarfed by the a mountain range known as the Taconic Mountains. These
were huge mountains were perhaps the size of today’s ________________. The Taconic Mountains along
the east coast and at Manhattan were eroded completely away except for the outcrops of Manhattan Schist.
3. Professor Johnson next visits southern ___________ where he looks into Zion Canyon. The 2,000 foot
sandstone cliffs are the remnants of a lost world. These were formed in the _______________ Period. At
this time much of the western part of the continent was a sea of sand dunes. This desert existed in the heart
of the largest continent ever formed. This supercontinent was named _____________________. The sand
desert was there because it was in the interior of Pangaea, far from any ocean and source of moisture,. So
what happened to that desert and to the supercontinent?
4. After a __________ million years Pangaea began to split apart allowing the formation of a new ocean, the
________________ Ocean. At about 150 million years North America drifted northward and the climate
began to change becoming more lush and less dry. North America was free again, but one important thing
was missing, the ________________ Mountains. These mountains are miles high and stretch from New
Mexico to Canada. Actually these majestic mountains have come and _____________ several times.
5. Next, Professor Johnson is playing golf just outside of the mile high city of __________________, Colorado.
At the 14th hole he meets a drone expert. The drone allows us to see the sandstone outcrops from above.
Since they are sandstone the sand that makes them up was originally deposited _________________. Taking
a closer look at the sandstone slabs gives us some clues about their origins. Mixed in with sand are
_________________ with sharp edges. Given the size of the pebbles, Professor Johnson thinks it is most
likely that the sediment of these slabs was deposited by a ______________________ that was probably
close to a mountain range. But what mountains? It can’t be today’s ____________________ because the
sandstone existed before they were formed. The mountains which produced the sandstone existed
___________ million years ago and have been worn down by erosion. These mountains are known as the
________________ Rockies. Something happened 70 million years ago to push up todays Rockies. But
what happened was hundreds of miles away on the ________________ edge of North America. A
subducting slab began pushing far inland under the continental crust instead of sinking into the mantle, and
it kicked up crustal North American rocks thus forming the “Rockies 2.0”. As these deep rocks were forced
up, they pushed up ____________ feet of layered rock laying above them. The sandstone was tilted up to
steep angles which erosion has carved in sharp slabs (now called the “flatirons”). The mountains that pushed
up the sandstone slabs were eventually mostly eroded, but then about _____________ years ago the entire
region including these eroded mountains was lifted a mile and more above sea level. This might be called
the “Rockies 3.0.” They are the modern Rockies and they are still rising.
6. Now we have only to form the west coast of North America. So Professor Johnson next takes us to look for
fossils by splitting slabs of rock at low tide along a remote beach in Alaska. After hours of searching he hits
the jackpot and finds fossilized __________________ fronds. The question is, what was a palm tree doing
so far north. It is too cold for them here today. On a neighboring island they have also found
________________ which are much older than the palms. Scientists think the corals, over 150 million years
ago, hitched a ride to Alaska with strings of _____________________. The scientists think the west coast of
North America was built over tens of millions of years by sticking foreign islands and mini-continents to
North America.
7. Professor Johnson next goes to San Francisco to visit Tomales Bay, just 30 miles north of San Francisco. It is
a long straight bay running from deep in the rugged coastal hills northwest to the Pacific Ocean. Geologist
Lisa White explains the strange situation here. The rocks are entirely different on the opposite sides of the
bay. This is because under the bay is an immense crack in the crust called the ________ ______________
Fault which runs through the bay. That fault separates two huge lithospheric plates, the North American and
the _____________________. The west side is moving to the northwest (relative to the east side) at a rate of
_________________ inches each year.