About 450 million years ago:

It was the Ordovician Period.  While marine species were
undergoing an explosion of evolution, there was little life on
land (though there was about to be an explosion of another
sort).  There were some slimy plants and fungi with possibly
some primitive arthropods starting to crawl about (there might
have been some worms even earlier).

There was no Lake Superior and the part of North America
where it now is, was south of the Equator.

Into this Utopia, streaking along at more than 12 miles/second
a large meteorite plunged into the atmosphere.  Nearly a mile
in diameter it struck the area destined to become the top of
Lake Superior with what would have been a catastrophic
impact ... if there had been anything to destroy.  The colossal
explosion left a crater nearly 20 miles in diameter, however the
primitive state of life on land raises the question of whether
anything heard it.
About a week ago:

It's the Neogene Period.  Animals and plants abound in
mind-boggling profusion of form and number (though
there is evidence we may be entering into another great
die-off).  

Lake Superior not only exists, but is the largest expanse of
fresh water on the globe, half way to the North Pole from
the Equator and famous for its cold clear water.

The meteorite crater; remnant of a calamity that if it
occurred today could end civilization, is unknown to most
of the people that live on or near it or to those who pass
along its edge on the Trans-Canada Highway.  The
dramatic central peak of the crater, heavily eroded over
Eons, is covered in a chaotic welter of plants, placidly
roamed by unconcerned caribou and surrounded by the
deep water of the lake. It now appears as an idyllic
archipelago seven miles offshore of Terrace Bay, Ontario;
the Slate Islands.
A fiery explosion of a
different kind
Photo by Rob Mullen
Woodland caribou bull on the
Slate Islands, September 4, 2008