Ancient super-floods deformed the Earth's crust

The last Ice Age melting ice floods changed the Earth's surface, leaving many traces that can still be seen today in North America.

The Channeled Scablands in eastern Washington state.

Traces of one of the greatest ancient floods still linger in eastern Washington state, in an area called the Channeled Scablands. For a long time, geologists struggled to understand the dynamics of these floods.

Using ancient superflood models, Tamara Pico, assistant professor of Earth and planetary sciences at the University of California, Santa Cruz, and colleagues examined whether glacial isostatic (GIA)-strain adjustment at Earth's crust as heavy ice sheets form and melt - affect the Channeled Scabland or not. They published their results in the journal Proceedings of the National Academy of Sciences.

"We used relatively simple but viable experiments to test whether GIA has a significant effect on the rate of flood discharge and erosion in two large swaths of Scabland, Cheney-Palouse and Telford-Crab Creek. no. We modeled the GIA to reconstruct the topography of the Channeled Scabland at different times during the late Ice Age flood," Pico said.

Geologists have found that the impact of melting glaciers on the Earth's crust is likely to play an important role in superflooding. GIA causes crustal deformation in the Channeled Scabland at a rate of 10 mm/year, many times the rate of tectonic ground uplift, thereby affecting flood discharge. The reconstruction of the event helped the team understand how floods shaped landscapes on Earth and Mars.

Ice shelves covered large areas of North America during the last Ice Age, but they began to melt about 20,000 years ago. The Missoula super flood is thought to have occurred 15,500 - 18,000 years ago. Lake Missoula formed when a large patch of the Cordillera ice shelf blocked the Clark Fork valley and melted glacial water accumulated in the background. Many factors combine to cause the ice sheet to break up, leading to a super flood. However, as the water overflows, the ice dam re-forms and the water continues to accumulate. The process may repeat several times over the next thousands of years. The team believes that the deformation of the Earth's crust due to the expansion of the ice shelf caused the elevation of the landscape to change by hundreds of meters during this period.