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'Midcontinent Rift'
About 1.1
billion years ago, in the middle of our country today there was a divergent
plate tectonic interaction that caused the crust of the Earth to begin splitting
apart and magma from deep inside the Earth to come up and fill in the split.
This interaction results in a huge basin that might become an ocean; in
Minnesota's case we got Lake Superior.
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| This map explains shows you where the 'Midcontinent Rift' occured http://prophecyfloodmid-continentriftsystem.blogspot.com/ |
Basalt
All along Lake
Superior's shoreline you can see Basalt, which is an extrusive, igneous and
mafic rock. An igneous rock is one that was formed from the cooling of magma
and extrusive means that the rock formed on the Earth's surface. Basalt is
comprised of mafic minerals, mostly Iron and Magnesium, which tend to be very
dark in colors. The massive amounts of basalt in Northern Minnesota is due to
when the 'Midcontinent Rift' occurred the massive amounts of magma that came up
to the Earth’s surface, forming much of the landscape we see today.
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| Here is a picture of Gooseberry falls, the basalt is all behind the waterfall http://www.planetware.com/i/photo/gooseberry-falls-state-park-two-harbors-mn160.jpg |
Gneiss
About 3,600
million years ago, Gneiss, a metamorphic rock was formed through the heating and pressure
from the Earth from the parent rock, granite. Gneiss has crystals that are very
coarse in grain size which tells us that the magma that formed this rock cooled
very slowly. Gneiss is a foliated rock, which conveys that the minerals are aligned
because of the massive amount of pressure they endured.
This is a picture of Morton Gneiss, a rock prevalent in Northern Minnesota
Granite
Granite is a
rock that is found mostly in northern Minnesota. Granite is an igneous,
intrusive and mafic rock. An igneous is one that formed from the cooling of
magma; an intrusive rock is one that cooled very deep inside the Earth. A mafic
rock means it is lighter in color and it consists mainly of Silicon and
Aluminum; Minnesota’s granite is mostly comprised of feldspar, quartz and mica.
Here is an example of Minnesota granite in it's natural state
Another picture of Lake Superior's Split Rock Lighthouse
Sources:
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