The slope of the earth’s crust dominated the flow of ancient floods

Massive floods from the Missoura floods were once poured into Dry Falls. The Dry Falls stretch 3.5 miles wide and fall 400 feet into a basin that is currently supplied with groundwater. Credit: Tamara Pico

When the ice sheet began to melt at the end of the Last Glacial Period, a series of floods called the Missoura Mega Flood struck the landscape of eastern Washington, with long, deep waterways and towering cliffs in what is now known as Channeled Scablands. I carved. They are one of the largest known floods in Earth’s history, and geologists struggling to reconstruct them have now identified key factors that govern their flow.

In a study published on February 14th Minutes of the National Academy of SciencesResearchers have shown how changes in ice sheet weight caused the whole thing Landscape Tilt and change the course of the mega flood.

“People have seen high places water Tamara Pico, an assistant professor of earth and planetary sciences at the University of California, Santa Cruz, said: The terrain of the Ice Age would have been different on a broad scale due to the deformation of the Earth’s crust due to the weight of the ice sheet. “

At the height of the Last Glacial Period, huge ice sheets covered much of North America. They began to melt about 20,000 years ago, and the Flood of Missoura occurred between 18,000 and 15,500 years ago. Pico’s team investigated how changes in ice sheet weight during this period could change the terrain of eastern Washington, changing the amount of water flowing into different channels during floods.

Glacier Lake Missoula was formed when Cordillera leaves were formed in western Montana. ice sheet It dammed the Clark Fork Valley of the Idaho Panhandle and melted the water that had accumulated behind the dam. Eventually the water became deeper and the glacial lake outburst began to occur. flood.. After sufficient water was released, the ice dam was resettled and the lake was replenished. This process is believed to have been repeated dozens of times over thousands of years.

The Columbia River, downstream of Lake Missoula, was blocked by another glacier, forming Glacial Lake Colombia. When the explosive floods of Lake Missoula flowed into Lake Columbia, water spilled south into the plateaus of eastern Washington, eroding the landscape and creating the Channeled Scablands.

During this period, the deformation of the crust in response to the growth and contraction of the ice sheet would have changed the elevation of the terrain by hundreds of meters, Pico said. Her team incorporated these changes into the flood model to investigate how landscape slopes changed megaflood routing and erosion power across different channels.

The slope of the earth's crust dominated the flow of ancient floods

Towering cliffs carved by the Flood of Missoura can be found throughout Channeled Scablands in eastern Washington. Credit: Tamara Pico

“We used a flood model to predict the velocity and erosion of water in each channel and compare it to what is needed to erode the basalt, the rock type of the landscape,” Pico said. I am saying.

They focused on two major channel systems, the Cheney-Palouse and Telford-Crab Creek tracts. Their results showed that early floods would have eroded both areas, but later floods would have concentrated the flow on the Telford-Club Creek system.

“As the landscape sloped, it affected both the flooded areas of Lake Colombia and the waterways of the waterways, but the most important impact was the spillover effect on these two areas,” Pico said. I am. “The interesting thing is that the terrain is not static, so you can’t just look at today’s terrain to reconstruct the past.”

The findings provide a new perspective on this fascinating landscape, she said. Steep canyons hundreds of feet deep, dry waterfalls, giant potholes and ripples are one of the many notable features carved into the landscape by massive floods.

“When you’re directly there, it’s crazy to think about the magnitude of the floods needed to carve those canyons that are now dry,” Pico said. “There is also a huge dry waterfall. It’s a very impressive landscape.”

She also said that the oral history of Native American tribes in the region contained references to massive floods. “Scientists weren’t the first to see this,” Pico said. “People may have been there to witness these floods.”

In addition to Pico, co-authors include Scott David of Utah State University. Isaac Larsen and Karin Lehnigk at the University of Massachusetts Amherst; Alan Mix at Oregon State University. Michael Lamb of the California Institute of Technology.

The “Mega Flood” in the western United States during the Last Glacial Period may not have been so mega

For more information:
Channeled Scablands glacier isostatic incision by ice age megaflood Minutes of the National Academy of Sciences (2022). DOI: 10.1073 / pnas.2109502119..

Quote: The Earth’s crust tilt is the ancient Megaflood (2022) taken from on February 14, 2022. February 14) dominated the flow

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The slope of the earth’s crust dominated the flow of ancient floods

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