Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
NOVA Home Find out what's coming up on air Listing of previous NOVA Web sites NOVA's history Subscribe to the NOVA bulletin Lesson plans and more for teachers NOVA RSS feeds Tell us what you think Program transcripts Buy NOVA videos or DVDs Watch NOVA programs online Answers to frequently asked questions

Explore the Scablands


Mystery of the Megaflood homepage

Scablands map

Thumb 01
Enlarge this image


1. Blackfoot River Valley
When Glacial Lake Missoula's ice dam shattered, a northern arm of the lake drained in a matter of hours through a narrow gap in Montana's Blackfoot River valley. One can only imagine the extraordinary upheaval that took place along this portion of the gap as the flood pounded through.


Thumb 02
Enlarge this image


2. Mission Mountains
One of the most striking signs that a vast lake once lay atop present-day Missoula and other parts of northwest Montana are the former shorelines etched into hills like this one in the Flathead River Valley. Backed by the Mission Mountains, the hillside lies about 10 miles south of Flathead Lake.


Thumb 03
Enlarge this image


3. Flathead River Valley
This river valley once lay at the bottom of Glacial Lake Missoula. When the lake drained catastrophically, its waters gushed (from right to left in the image) over the ridge at right, depositing a bar of sand and gravel in a tributary valley (center). Locals call these deposits "gulch fillings."


Thumb 04
Enlarge this image


4. Camas Prairie
In the early 1940s, geologist Joseph Pardee first identified these wavy landforms as ripples not unlike those seen in the bed of a stream. No one had thought of them as ripples before because of their outlandish size: up to 35 feet high and several hundred feet between crests. The ripples provide perhaps the strongest evidence for monstrous ancient floods.


Thumb 05
Enlarge this image


5. Clark Fork River
Imagine a glacier filling this valley so that only a few mountaintops poked above the ice. The glacier, a southern tongue of the great Cordilleran ice sheet that covered western Canada in the last ice age, dammed up the Clark Fork River, creating Glacial Lake Missoula. When the ice dam (which stood in the far right of this image) burst under the lake's enormous pressure, up to 500 cubic miles of water barreled down this valley in just 48 hours.


Thumb 06
Enlarge this image


6. Scabland Coulee
The floods left behind "coulees"—dry streambeds or gullies—all over what is now eastern Washington. Here, an old homestead sits in the bottom of a coulee within the "scablands," the term early settlers gave to the region's flood-scoured lands. Sagebrush blankets the steep, flood-cut slopes, while above them wheat fields take advantage of rich soils the floods didn't reach.


Thumb 07
Enlarge this image


7. Palouse River Canyon
Geologists have long known that the modern-day Palouse River is too modest a creek to have carved these massive canyons. Lying just north of the river's confluence with the Snake River, these basalt canyons provide further evidence that giant floods thousands of years ago did the brunt of the work.


Thumb 08
Enlarge this image


8. Dry Falls
This lake is one of a number of plunge pools left behind when Glacial Lake Missoula's debris-clogged waters rushed over the rocky precipice known today as Dry Falls. Picture floodwaters more than 250 feet deep pouring over a falls five times wider than Niagara, and you get an idea of the immensity of the flood. Note the huge, water-carved potholes known as "kolks" (at right in image).


Thumb 09
Enlarge this image


9. Lenore Caves
South of Dry Falls, in a stretch of flood-chiseled canyon called the Lower Grand Coulee, raging waters gouged out holes in the basalt cliffs, forming shallow caves like this one. Archeologists have found evidence that Native Americans lived and stored goods in these caves.


Thumb 10
Enlarge this image


10. Frenchman Spring Coulee
Remarkable as it seems, this now-dry waterfall (cliffs in background) periodically vanished underwater as Glacial Lake Missoula floodwaters, muddy with sediment and debris, drained thunderously off the Quincy basin into the Columbia River. The glacial water continued wreaking havoc all the way to the Pacific Ocean.


Thumb 11
Enlarge this image


11. Saddle Mountains
Flowing south (left to right in image), the biggest floods actually overtopped portions of the Saddle Mountains seen here, which gives an idea of just how much water was involved. Crab Creek Coulee, shown here, lies just south over a ridge of mountains from Frenchman Spring Coulee.


Thumb 12
Enlarge this image


12. Rowena Gap
At places like Oregon's Rowena Gap (seen here), the Columbia River Gorge served as a bottleneck that piled up waters from the floods to heights reaching 1,000 feet. The gorge's andesite bedrock, including the rugged cliffs found in this spot between the towns of The Dalles and Hood River, reveals scars of this almost unimaginable assault.


Thumb 13
Enlarge this image


13. Multnomah Falls
The floods left near-vertical walls along portions of the Columbia River Gorge, resulting in spectacular waterfalls like Multnomah, the second-highest year-round waterfall in the U.S. After flowing down from Larch Mountain, Multnomah's spring-fed waters plunge over 600 feet into the gorge, a spectacle that draws thousands of tourists each year.


Thumb 14
Enlarge this image


14. Willamette Valley Erratics
Courtesy of the floods, Oregon's fertile Willamette Valley boasts not only rich soils that once mantled the scablands far to the east but also glacial "erratics" (rocks carried far from their site of origin). Geologists believe these erratics arrived inside icebergs caught in a Glacial Lake Missoula flood. When the bergs grounded and melted here, the rocks were left high and dry, hundreds of miles from where they once lay.


Back to top




Mystery of the Megaflood
Megafloods

Fantastic Floods
Geologist Vic Baker on giant floods and what they can teach us

Ice Age Lake

Ice Age Lake
What Glacial Lake Missoula was like before it burst

Explore the Scablands

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

What on Earth Made This?

What on Earth
Made This?

Try our gee-whiz geology quiz.



Send Feedback Image Credits
   
NOVA Home Find out what's coming up on air Listing of previous NOVA Web sites NOVA's history Subscribe to the NOVA bulletin Lesson plans and more for teachers NOVA RSS feeds Tell us what you think Program transcripts Buy NOVA videos or DVDs Watch NOVA programs online Answers to frequently asked questions

Support provided by

For new content
visit the redesigned
NOVA site