Ice Age Floods National Geologic Trail NPS

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Ice Age Floods National Geologic Trail NPS Discover the geologic story of the last Ice Age Floods. This trail travels across Montana, Idaho, Wa Please be considerate of other fan's opinions.

“At the end of the last Ice Age, some 12,000 to
17,000 years ago, a series of cataclysmic floods
occurred in what is now the northwest region
of the United States, leaving a lasting mark of
dramatic and distinguishing features on the
landscape of parts of the States of Montana,
Idaho, Washington, and Oregon.”



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Photo Submission Guidelines:

We have decided to allow photo sharing for contests. When we run a photo contest, the Wall will be open for 3 days for you to post photos. We want you to share your photos, so everyone is allowed to submit. National park photos are beautiful, but photos submitted here must be of the Ice Age Floods National Geologic Trail. Please caption your photos with location and subject for others to read. Comments on photos are welcome, but please adhere to our posting regulations found in our Info section. Photos may not contain any nudity or pornographic content. The photo(s) containing such content will be removed and you will be banned from the site. Photos may not show activities that would be a violation of park rules or laws. The photo(s) containing such content will be removed. Photos may not contain any watermarks or references to websites or commercial businesses. Photos you post should belong to you and be photos that you have taken. Please respect copyright laws and do not post photos that do not belong to you. Once a photo has been posted, it is out there for all to see. Use your best judgment as to what you want everyone to see. Due to privacy concerns, people in photos should not be recognizable. Do not post photos with minors. The photo(s) containing such content will be removed.
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The cliff in this image, at Hells Gate State Recreation Area in Idaho, preserves pieces of a much larger Ice Age story, ...
09/09/2026

The cliff in this image, at Hells Gate State Recreation Area in Idaho, preserves pieces of a much larger Ice Age story, two very different floods recorded in stone.

The lower, boulder‑rich layers mark the Bonneville Flood, an earlier single megaflood unleashed when ancient Lake Bonneville in Utah, Idaho, and Nevada overtopped its natural barrier. That high‑energy surge raced north through the Snake River system and into Hells Canyon, powerful enough to move large rounded cobbles and coarse gravels. These thick, chaotic deposits form the base of the slope.

Above them, the fine, rhythmically layered sediments tell a quieter tale. They were left by the Ice Age Floods from Glacial Lake Missoula. When those repeated floods reached Wallula Gap, the narrow bottleneck slowed their force and created temporary Lake Lewis. In this slackwater, sediments settled gently, building the horizontal bands preserved higher on the cliff.

Read from bottom to top, the cliff becomes a timeline:
• Bonneville Flood — fast, coarse, high‑energy
• Missoula Floods — slow, layered slackwater deposits

Together, they form a geologic mosaic—two floods, two energies, two eras—captured in one place. And this is just one chapter in the broader landscape interpreted along the Ice Age Floods National Geologic Trail, where visitors discover the clues left behind by some of the largest floods on Earth.

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Did you know that some canyon walls hold the secrets to ancient, vanished rivers?Take a close look at the cliff line in ...
09/04/2026

Did you know that some canyon walls hold the secrets to ancient, vanished rivers?

Take a close look at the cliff line in this photo from Washington’s Grand Coulee. See that distinct dip along the top rim that just stops in mid-air? That is a geological feature known as a hanging valley.

During the last Ice Age, catastrophic megafloods from Glacial Lake Missoula tore through this region. The immense hydraulic force rapidly plucked away massive layers of dark columnar basalt, dropping the main canyon floor by hundreds of feet in a matter of days. This left smaller, pre-existing side valleys stranded high up on the new cliff walls.

When geologist J Harlen Bretz used these perched channels to argue for a massive ancient flood in the 1920s, his peers were highly skeptical. Decades later, modern science proved him right, turning these volcanic cliffs into a masterclass in Earth history.

Have you ever spotted one of these unique formations while exploring the Ice Age Floods National Geologic Trail? Let us know in the comments!



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Address

1008 Crest Drive
Coulee Dam, WA
99116

Telephone

+15097547800

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