Also, the area of basalt distribution is square rather than elongate. On many of the maps, the area of Columbia River Basalt looks a lot darker than it does on the legend. The CRB's area is the big squarish area that straddles the OR-WA state line and follows the Columbia River to the Ocean. Most of the eruptions were at about 16 Ma. Rocks of the Cascade Volcanoes.
Good luck getting ready and afterwards, have a great summer.