Before revision: Front of the main building of the David A. Johnston Cascades Volcano Observatory The David A. Johnston Cascades Volcano Observatory (CVO) is the volcano observatory that monitors volcanoes in the northern Cascade Range , formed .
After revision: Front of a main building of the David A. Johnston Cascades Volcano Observatory The David A. Johnston Cascades Volcano Observatory (CVO) is the volcano observatory that monitors volcanoes in the northern Cascade Range .