50,000 Years Ago

This isn’t the first time I’ve written about Meteor Crater. I’ve been there twice and highly recommend this National Landmark to all Arizona visitors. It’s an awe-inspiring experience. This week I’m writing about some fascinating new research connecting Meteor Crater to a paleolake (an ancient lake that no longer exists) in the eastern Grand Canyon.

Research by K.E. Karlstrom et al., 2025, indicates the meteorite impact that caused Meteor Crater may have also caused a massive landslide in the Grand Canyon, temporarily damming the Colorado River. The landslide created a lake nearly 6 miles long. This paleolake has been dubbed “Nankoweap paleolake” for the geological sediments in the region. The Nankoweap Formation is a thin sequence of distinctive layers that consist of reddish brown and tan sandstones and subordinate siltstones and mudrocks.

Karlstrom was investigating caves high up the cliffs in Marble Canyon, pictured here:

What he found was, in caves nearly 150 feet above the current river level, there was driftwood that could be carbon dated to around 56,000 years ago, as well as silty deposits of sediments. Interestingly, he also found petrified beaver tracks. Clearly the water level was much higher in the past.

“That would have required a 10X bigger flood level than any flood that has happened in the past several thousand years,” says Karlstrom, co-lead author of the study, and an Earth and planetary science professor at the University of New Mexico.

Curiously, Meteor Crater was formed roughly 50,000 years ago, based on several geologic analyses. That was close enough to the age of Nankoweap paleolake to inspire Karlstrom’s research.

As for the landslide trigger, the meteor would have generated an earthquake of magnitude 5.4–6.0 near the impact site. The shockwave would have attenuated to around magnitude 3.5 by the time it got to Marble Canyon — 100 miles distant. That could still cause a landslide given the unstable nature of canyon walls.

At some point, the lake had to breach the dam. The Colorado River watershed drains 250,000 square miles of land, tapping both rain and snowmelt. Despite droughts, the water is destined to accumulate long term. The breach would have started as a small waterfall some 200 feet high, but as the water eroded the dam, flow would have steadily increased. The lake probably drained completely, eroding the dam down to bedrock, within a thousand years. 

The researchers noted that further study is required to eliminate any other possible explanations for the river damming, such as random rockfall or a local earthquake around the same time. But from the cave data, there’s no doubt Nankoweap paleolake existed.

Next Week in Sky Lights ⇒ How Riptides Form