Mt. Baker in Washington is the northernmost of the major Cascade volcanoes. The actual cone measures 6000 feet in height and 8 miles in diameter. The craterrim, however, is 10,750 feet above sea level as the base of the volcano rests on top of the Cascade range. The lavas of Mt. Baker poured out on an erosion surface of Paleozoic and Mesozoic rocks which had a relief of approximately 5000 feet.
The first flows formed a cone known as the Black Buttes, then the vent shifted 2 miles to the east and formed Mt. Baker. These lavas are noteworthy because of their lack of variation; all are pyroxene andesites. Almost all the lavas contain a type of hypersthene with inclined extinction.
The lavas from Mt. Baker and the subsidiary vents probably began to form in the Pleistocene, and activity continued until historic time.