Pumice/scoria distribution is a side a business for a trucking company that otherwise specializes in agricultural trucking services.
This scoria is a Washington State product from the Goldendale area. The Cascades of south-central Washington better reflect what one might call the pure Cascade Range - a broad uplift covered with volcanoes including considerable number of cinder cones. The North Cascades are really a multiple tectonic mélange of various accreted terrains. Cinder cones are rare in the North Cascades, but there is one near Mount Baker (nwgeology/the-cinder-cone-in-schreibers-meadow).
The availability of this material for geotechnical engineering or engineering projects can solve some tricky problems where low density fill is needed. And an added benefit is the light weight for trucking gives it a better range for use as hauling costs per ton is no small thing.