Between 20,000 and 110,000 years ago, a period of volcanism resulted in a flow of lava which met an obstacle in what is now the valley of the Cowlitz River's Clear Fork. Although the nature of the obstruction is not known, the volcanic extrusion of dacite formed a deep pool and congealed under particular conditions, allowing the lava to 'crystallize' into basaltic columns. Subsequent erosion by wind and water have left the formations exposed to view here at the Palisades.
Originally, I had thought to submit this as an Earthcache, but my love of the hunt and trinkets persuaded me that others might feel the same. Please take a few minutes to admire the geology before searching for the hidden container nearby (small decon.).