The geology of the Grand Canyon area exposes one of the most complete
sequences of rock anywhere, representing a period of 1.4 billion years
of the Earth's history in that part of North America. The major
sedimentary rock layers exposed in the Grand Canyon and in the Grand
Canyon National Park area range in age from 2 billion to about 200
million years old. Most were deposited in warm, shallow seas and near
ancient, long-gone sea shores. Both marine and terrestrial sediments
are represented, including fossilized sand dunes from an extinct
desert. Uplift of the region started about 75 million years ago in the
Laramide orogeny, a mountain-building event that is largely
responsible for creating the Rocky Mountains to the east. The canyon
did not start to form until 5.3 million years ago when the Gulf of
California opened up and thus lowered the river's base level (its
lowest point) from that of large inland lakes to sea level. About 2
million years ago volcanic activity started to deposit ash and lava
over the area. The nearly 40 identified rock layers and 14 major
unconformities (gaps in the geologic record) of the Grand Canyon form
one of the most studied sequences of rock in the world.
Read the rest of this article:
http://en.wikipedia.org/wiki/Geology_of_the_Grand_Canyon_area
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Today's selected anniversaries:
1817:
The Bank of Montreal, Canada's oldest chartered bank, opened in
Montréal, Québec.
(
http://en.wikipedia.org/wiki/Bank_of_Montreal)
1917:
Arthur Balfour issued the Balfour Declaration, proclaiming British
support for Jewish settlements in Palestine.
(
http://en.wikipedia.org/wiki/Balfour_Declaration%2C_1917)
1936:
BBC Television Service, the oldest television station in the world,
was launched.
(
http://en.wikipedia.org/wiki/BBC_One)
1947:
Howard Hughes flew Spruce Goose, the largest flying boat ever built,
on its maiden flight in Long Beach, California.
(
http://en.wikipedia.org/wiki/Spruce_Goose)
2000:
The first crew arrived at the International Space Station.
(
http://en.wikipedia.org/wiki/International_Space_Station)
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Wikiquote of the day:
"Courage! I have shown it for years; think you I shall lose it at the
moment when my sufferings are to end?" -- Marie Antoinette
(
http://en.wikiquote.org/wiki/Marie_Antoinette)