Mystery of the Megaflood

The mystery of the megaflood is an interesting topic that has baffled geologists and has challenged the scientific community's view on how the world changes over a period of time.  The video goes through the process of how the Scablands were produced not over a long extended period of gradual change, but rather by the immediate change of intense glacier flooding.  To be specific, the video describes a 4 step process that creates the changes we observe in the Scablands.

The first is super cool water.  This water is below the freezing point but remains a liquid because of the pressure within the glacier leaves no room for expansion.  The water then forces its way through fractures in the glacier, melting the ice, and causing weakness in the glacier's stability.

The second is the collapse of the ice dam.  Because of the immense amount of pressure built up by the super cool water, the glacier or ice dam collapses causing a surging flood.

The third step is the rush of water, up to 60 mph, toward the scablands. This wall of water was up to 800 feet deep.  It gorged out miles of rock, carved cliffs and canyons (dry falls), created underwater tornados which blasted out potholes, and it deposited random boulders that had accumulated in the glacier over the Scab Lands that were randomly thrown aside as the flood lost its momentum.

The fourth step is the amount of time it took the water to surge out to sea in the Pacific ocean.  Within a few hours all evidence of the dramatic flood had vanished and had left behind only the confusing landscape of potholes, erratics, dry falls, ripples, and multi-layerd sediment.

The video ends by saying that there was not only 1 giant flood that caused the formations of the Scablands, but it was the result of multiple floods; a cycle of giant floods rocked the Scablands!

Visit these sites for more information:
http://www.pbs.org/wgbh/nova/earth/explore-the-scablands.html