Earth Photography: It's Harder Than It Looks

On Mon, 27 Feb 2012 17:11:23 -0500, Alan Browne
wrote:
: On 2012-02-27 15:29 , me wrote:
: http://blogs.nasa.gov/cm/blog/letter...118334979.html
:
: Cool photo - for the aurora.
:
: Also, easily identifiable is the circular Manicouagan Reservoir -
: created by damming a river for hydro power (about 5000 MW in a series of
: 4 dams). The circle is the eroded remnant of a crater created by a
: meteor impact some 200 M years ago.

What made the circle lower than the surrounding ground? IOW, how did damming
the river ensure that the water would remain in the circle? Did they build an
artificial outer wall?

Bob

On 2012-03-01 19:15 , Robert Coe wrote:
On Mon, 27 Feb 2012 17:11:23 -0500, Alan Browne
wrote:
: On 2012-02-27 15:29 , me wrote:
: http://blogs.nasa.gov/cm/blog/letter...118334979.html
:
: Cool photo - for the aurora.
:
: Also, easily identifiable is the circular Manicouagan Reservoir -
: created by damming a river for hydro power (about 5000 MW in a series of
: 4 dams). The circle is the eroded remnant of a crater created by a
: meteor impact some 200 M years ago.

What made the circle lower than the surrounding ground? IOW, how did damming
the river ensure that the water would remain in the circle? Did they build an
artificial outer wall?

http://en.wikipedia.org/wiki/Manicouagan_Reservoir

The article on Wikipedia explains it as "an eroded crater". Since 214M
years there has been an ice age (or more), tectonic uplift, etc. as well
as plain old erosion. (Compare to Arizona's "Meteor Crater" which is
only 50,000 years old - eg: over 4,000 times older.)

No walls. AFAIK, a single dam formed the lake from the existing crater
by damming the river to the south. In terms of ROI to backup some water
for power, probably one of the best. I guess the surveyors and
engineers did a great job in picking out the site and studying its
potential.

--
"I was gratified to be able to answer promptly, and I did.
I said I didn't know."
-Samuel Clemens.