Tom Pierson, retired USGS Geologist/Hydrologist, will present an overview of the catastrophic forces and events that have shaped the Columbia Gorge that we know today.  Our majestic ancient river has fended off unceasing, violent geologic attempts to block it and divert it, but it keeps on flowing--it's quite a story. Tom will describe how small and huge volcanic eruptions, colossal floods, enormous landslides, and the grinding forces of tectonic crustal deformation have all taken their shots, yet the Columbia still flows to the sea. If you know where to look, you can see the evidence of these old heavyweight knockout rounds.   This talk will be hosted by the Columbia River Gorge Chapter of Ice Age Floods Institute at the White Salmon Community Library, beginning at 5:30pm on Monday, April 28.