15:00

USGS Jim O'Connor mapping, soil zones

"The soils in eastern Washington that were stripped off and then delivered here have a lot of volcanic materials in it which weather into important nutrients that plants need." Jim O'Connor, like Richard Waitt, is a U.S. Geological Survey geologist. O'Connor's work has produced a so-called "footprint" of Missoula Flood deposits in the Willamette Valley. The roiling Missoula Flood waters got here because the valley is downhill from Missoula. "So in yellow, you see these zones of soils that were very much influenced by the series of Missoula Floods, the glacial floods."

15:20

University of Oregon ongoing study, people at computers, David Hulse

At the University of Oregon, an ongoing study of how human beings use the land confirms the impact of the floods locally. David Hulse heads the U of O's section of Pacific Northwest Ecosystem Research Consortium. The organization includes universities and the Environmental Protection Agency. He describes the flood's influence on how people live in the Willamette Valley.

15:55

computer, how floods affected agricultural uses

"It has conditioned the kinds of agriculture that occurs in those areas. It has conditioned mostly the agricultural uses of those lands." Willamette Valley farmers enjoy rich soil formerly covering the scablands.

16:15

aerial view

That's because tributaries of the Snake and Columbia Rivers channeled the floodwater pretty much directly from eastern Washington to western Oregon. And yet, the flood's legacy is not a simple litany of winners and losers.

16:30

east end of the Columbia Gorge, clues to geography as focus of flood

We know the water got up at least a few hundred feet higher than we are now. To Richard Waitt and Jim O'Connor, it is an ongoing detective story with plenty of hidden drama yet to reveal itself. We are at the east end of the Columbia Gorge. Clues unearthed here point to how the geography of the terrain focused the floods' power as they entered the narrow Gorge.

"This is a site several hundred feet above the river, so you know the water had to get up to this level and go higher. Such a vigorous current was able to transport boulders of this size."

Pause tape and ask:

What clues might prove the flood waters were focused?

17:15

scars on Gorge, computer animation of debris in water "payload"

Scars left by the powerful current mark the high narrow walls of the Gorge to this day. It is evidence that the water got deeper and deeper. As water filled the narrow channel, the depth reached more than a thousand feet. The flow accelerated to 90 miles an hour, gathering an increasing payload of debris. The Gorge contained most of the raging water -- an overwhelming torrent aimed directly at what is now Portland.

17:40

helicopter of Phillipi Canyon leading into the John Day River

But at Phillippi Canyon -- and other locations -- the torrential slurry of dirt and rock and ice overflowed the Gorge. A dry channel is the indelible record of a monumental spillage from the Columbia Gorge at Phillipi into the John Day River. The waterfalls and islands in the channel testify to the violence of what was only a sideshow. Despite its power to drastically alter the land, this secondary spillway did nothing to ease the cataclysmic rush of floodwater.

18:25

west end of the Columbia Gorge, ocean waves

The west end of the Columbia Gorge feeds directly onto the plain now occupied by Portland, Oregon and its suburbs. The sounds of the floodwater -- boulders tumbling and shattering in the torrent -- could have been heard for miles.

18:40

animation of flood filling Willamette Valley, short-lived inland sea

The 400-foot wall of water would have leveled everything in its path. It filled the Portland basin and then raced south to turn the Willamette Valley into a short-lived inland sea.

Such a flood today, of course, would devastate the region. As it is, developers, civic authorities, and the general public must still deal with the aftermath of the flood.

Pause tape and ask students to predict:

What would happen if this flood occured today?

How has the flood affected west and east Portland?

19:10

State Department of Geology and Mineral Industries, Jerry Black, deposits increase earthquake threat because of deposits

"All things being equal we would expect more damage in the areas colored red." A map of earthquake hazards has been prepared here at the State Department of Geology and Mineral Industries. "The reasons it's red here is related to Missoula Flood deposits, absolutely." State Geologist Jerry Black says 50-foot-thick Missoula Flood deposits at Portland's western suburb of Beaverton increase earthquake threat there. The deposits may make the ground unstable in some parts of Beaverton if the ground begins to shake.

20:00

huge boulders in east Portland

And yet, perhaps the greatest flood impact can be found in east Portland. Near the mouth of the gorge, the floodwaters spewed huge boulders and mountains of gravel. Some of the topographical changes brought by the flood are so huge they go unnoticed.

20:10

Rocky Butte, Jerry Black's computer model of Portland

"When you hit, for instance, Rocky Butte, you can see where the water banged into the Butte, formed the bar behind it, wrapped around, and carried out a flood channel." State Geologist Jerry Black has produced a computer model of Portland. The model relies on survey information. All buildings, roads, and vegetation are eliminated. The model shows turbulent currents at the bottom of the flood deposited a huge gravel bar just west of Portland's Rocky Butte.

20:50

Alameda Ridge, ground stable due to size of rocks dropped

"The scale of this is much, much bigger. The scale of the bar runs for several miles -- and Alameda Ridge is the base of that bar." Alameda Ridge -- a comfortable Northeast Portland neighborhood -- is built on a Missoula Flood gravel bar. Of course, the water was about 400 feet deep -- another hundred feet above us here more or less -- and moving, probably, at several feet per second. By the time you get this far down, the flow has dropped most of the big stuff. The current has diminished, but it's still big enough to carry cobbles that are two to three inches in diameter. "The size of the rocks dropped here makes the ground stable. Flood deposits don't magnify earthquake danger on Alameda Ridge."

21:45

"calling cards" of the Missoula Floods, boulder floating on flood

Impact on soil and topography aside, the Missoula Floods left calling cards of their cataclysmic visits to Portland and the Willamette Valley. "It's most likely that this rock came from British Columbia ... "

22:00

animation of icebergs rafting on flood, bringing rocks with them, erratics

" ... probably transported by an iceberg floating in one of the floods." Because the Missoula Floods marked the end of an ice age, huge icebergs might well have been rafted hundreds of miles. Some must have carried a cargo of stone -- stone ripped from mountains as the glaciers carved them up.

22:25

erratics

The largest of such rocks -- called erratics -- known to be in the Willamette Valley is just west of McMinnville. "I suspect that a lot of rocks like this are buried out in the silts of the lowland here. It's just the ones that are up near the upper margins of the flow -- where they were beached up against the hill slopes, up above the lowlands -- that we see."

22:45

scoured land

The floods scoured away thousands of miles of the Earth's surface.

22:55

map of Oregon from space

The scars are clearly visible from outer space and resembled the flood-ravaged landscape of Mars. And yet, Willamette Valley and Portland deposits nothwithstanding, most rock and soil lifted away by the flood has never been found. There's far too much missing. "There's less than a hundredth, probably, of the material that's been removed from this system that we can account for in the gravel bars."

Pause tape and ask students to predict:

Where do you think the missing rock and soil from the floods is today?

23:20

beach waves, helicopter of the Gorge, glaciers calving, sunset

Somewhere under the Pacific, then, lies a mountain of rubble that was the Earth's skin. It washed here as the Columbia River ran at 2,000 times its average flow.

No glaciers are forming ice dams that threaten to turn parts of the Western U.S. into an inland sea. But that is scarcely the final word. The collective memory of human civilization is short, but time is long. And scientists believe there will be another ice age.

Pause tape and ask students to predict:

Could the floods happen again?

What conditions would need to be present for a similar flood?

Do you think humans would be able to prevent or lessen the effects of these floods? Why or why not?

Time Marks: 0:00-5:00 | 5:00-10:00 | 10:00-15:00 | 15:00-23:20