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How was the geologic puzzle solved?

It was in 1923 that J Harlen Bretz published the first in a series of scientific papers in which he proposed that the severely eroded Channeled Scabland, Dry Falls, and other immense geologic features had been formed by a huge, powerful flood that had swept through the Columbia Basin during the Ice Age.

Despite his peers’ doubt and opposition, he resolutely maintained that direct examination of the geologic evidence could lead only to that conclusion. But Bretz was unable to identify the source or cause of such catastrophic flooding.

Earlier, in 1910, another geologist, Joseph T. Pardee, had described evidence of a great ice dammed lake, Glacial Lake Missoula, that had formed during the Ice Age in northwestern Montana. However, Bretz didn't see the connection between the glacial lake in Montana and the features he described in Eastern Washington. Then, in 1940, Pardee reported on his discovery of giant ripple marks, 50 feet high and 200-500 feet apart, that had formed on the floor of Glacial Lake Missoula. These huge, current-related features, along with other newly-found landforms, dramatically confirmed that the lake had suddenly emptied to the west, unleashing the tremendously powerful erosive forces that shaped many of the landforms found in the Columbia Basin.

More research followed, and new perspectives became available from aerial photography. Among geologists, the concept of a catastrophic flood came to be accepted by the late 1950s.

In the following years the account was refined, as evidence of more than one flood was discovered. It is now established that there were large numbers of Ice Age floods that swept across the Northwest, and some of them were among the largest and most powerful floods that have ever occurred on Earth.

more:
What are the Ice Age Floods?
How did these floods happen?
Phenomena related to the Ice Age Floods

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