The two crossword solutions for the term MOUNT ___, COLO. are ETNA (4 letters) and OSO (3 letters). Etna is an active stratovolcano on the east coast of Sicily, Italy, in the Metropolitan City of Catania. It is the highest active volcano in Europe and one of the most active in the world. Oso is a census-designated place in Snohomish County, Washington, United States. It is located near the Stillaguamish River, about 50 miles north of Seattle.