Complex sentence: While many of the volcanic peaks in Oregon stand astride the Cascade Crest, Adams is the only active volcano in Washington to do so and is further east than all the rest of Washington's volcanoes except Glacier Peak.
Split into simpler sentences: While many of the volcanic peaks in Oregon are located on the Cascade Crest, Adams is the only active volcano in Washington to do so. It is further east than all the rest of Washington's volcanoes except Glacier Peak.