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Next on NOVA: "Mystery of the Megaflood"

http://www.pbs.org/nova/megaflood

Broadcast: May 16, 2006 at 8 p.m. ET/PT (Repeat)

(NOVA airs Tuesdays on PBS at 8 p.m. Check your local listings as
dates and times may vary.)

One of the Earth's strangest geological riddles is the evidence for
a huge catastrophe that struck eastern Washington State thousands of
years ago. It took scientists decades to figure out that a colossal
flood had carved out bizarre landscape features strewn across
thousands of square miles. On "Mystery of the Megaflood," NOVA gets
to the bottom of what created this compelling detective story. The
program features a dogged geologist sticking to his bold theory for
decades despite virtual professional banishment. Eventually, other
geologists joined his cause and filled in the intricate details,
which NOVA recreates in stunning computer animation to show what may
be one of the most spectacular series of events ever to occur on
our planet.

Here's what you'll find on the companion Web site:

Interview & Article

Fantastic Floods
In this interview, learn what megafloods can tell us about Mars,
the nature of science, and more.

Ice Age Lake
What would Glacial Lake Missoula have looked like before its
disastrous emptyings? Find out here.


Interactives

Explore the Scablands
Examine the evidence left by the violent floods.

Stumbling Upon a Treasure
Try your hand at our gee-whiz geology quiz.

Also, Links & Books, the Teacher's Guide, the program transcript,
and more.

http://www.pbs.org/nova/megaflood

[Guest_Richard Trigaux_*]

Interesting, pity they don't provide aerial views to compare with Mars floods.

[ElkGroveDan]

This is why hardly anyone builds major dams out of ice any more.

Interesting, pity they don't provide aerial views to compare with Mars floods.

[Bob Shaw]

Richard:

Um. Victor Baker is, and always has been, a *leetle* bit enthusiastic about the scablands... ...I confess that catastrophism is not a style of geology which I find enticing! Still, dramatic things can happen - I simply prefer long, slow processes to have been considered to death *first*...

...and there's lots of comparison photos between the scablands and Mars in his book, but they all suffer from being what (today) we have to call low-res Mars images.

Bob Shaw

[Guest_Richard Trigaux_*]

Hmmmm... difficult to conclude, with only Google Earth. We see more corn fields shapes than geological shapes.

Richard:

Um. Victor Baker is, and always has been, a *leetle* bit enthusiastic about the scablands... ...I confess that catastrophism is not a style of geology which I find enticing! Still, dramatic things can happen - I simply prefer long, slow processes to have been considered to death *first*...

...and there's lots of comparison photos between the scablands and Mars in his book, but they all suffer from being what (today) we have to call low-res Mars images.

Bob Shaw

Yes, I am not convinced that there was such a large flood here, although it is still perfectly possible.

Large floods from glacial lakes are a very real phenomenon in the Himalayas, where there are regularly catastrophic "flash floods" when a glacier or a moraine breaks. In Bhutan it happened several times recently, and in Nepal there is a legend on a valley completelly destroyed with all its inhabitants, and the traces of a huge landslide are actualy visible in the place. There are also traces of this in France, in the Pyrenées. That such phenomenon could happen at a larger scale is possible.

The problem is that short large floods can quickly erode sands or clays, but they will most of the time left rocks in place. This anyways poses a problem with large flood valleys on mars, which look as if they were carved in sand, when we know they are carved into lava flows. We never see for instance a large valley narrowing when it comes into a mountainous place.

I think we should not reanimate the old debate between catastrophism and slow processes. It was a debate some centuries ago, but now in front of all the variety of processes we know are working into geology, such a distinction/opposition don't make sense. In France there are large lava flows 30kms long, and on Venus the record is set at 6000kms! not to speak of the catastrophes at best: large meteorite impacts, with all the strong modification they provoque into biology and climate.