Nothing characterizes the volcanic legacy of Crater Lake quite like the Pinnacles that rise above Sand Creek outside the caldera. The needle-like formations consist of pumice and ash layers deposited as Mt. Mazama erupted. These “fossilized fumaroles” were cemented by dissolved minerals and hot gasses rising through the pumice and ash. Subsequent erosion of finer, less resistant materials left the pinnacles behind, which tower as high as 200 feet above the valley floor.