Geologists believe these erratics arrived inside icebergs caught in a Glacial Lake Missoula flood. When the bergs grounded and melted here, the rocks were left high and dry, hundreds of miles from ...

Fifteen thousand years ago, during the last Ice Age, a glacial dam collapsed in what is now northern Idaho, releasing the waters of a giant inland sea known as Lake Missoula. Five hundred cubic ...

The great continental ice sheets were melting very fast in the time of Glacial Lake Missoula, shedding great ... but even then, the flood probably swept most of them along. So boulders that ...