"Now, in a recent study published in Geology, retired University of New Mexico geologist Karl Karlstrom and his colleagues conclude that the asteroid's impact shook Marble Canyon hard enough to dislodge great chunks of stone and send a landslide tumbling into the river. The debris formed a natural dam that backed up the Colorado for over 50 miles to near present-day Lees Ferry."
"IN THE 1960s, Karlstrom's father, also a geologist, and several other scientists entered Stanton's Cave, 32 miles downstream of Lees Ferry. Inside, they found loose sediment and driftwood nearly 150 feet above the river. Later, U.S. Geological Survey geologist Richard Hereford developed a hypothesis: Something must have dammed the river, forming a lake. But with just the Stanton's Cave evidence and a squint-to-see-it possible ancient dam site 20 miles downstream at Nankoweap Canyon, the younger Karlstrom "never believed (Hereford's) story, frankly.""
An asteroid impact at Meteor Crater about 56,000 years ago produced seismic shaking that dislodged rock in Marble Canyon, triggering a massive landslide into the Colorado River. The landslide debris formed a natural dam that backed the river up more than 50 miles toward Lees Ferry, producing a lake comparable in size to modern Lake Mead. The backed-up waters flooded canyons and caves and left sedimentary traces hundreds of feet above the current river level. Geologic evidence in caves includes loose sediment and driftwood found well above the modern river, pointing to past highstands caused by river blockage.
Read at High Country News
Unable to calculate read time
Collection
[
|
...
]