Mount St. Helen's is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United States. It is 96 miles (154 km) south of Seattle, Washington and 50 miles (80 km) northeast of Portland, Oregon. Mount St. Helen's takes its English name from the British diplomat Lord St Helen's, a friend of explorer George Vancouver who made a survey of the area in the late 18th century. The volcano is located in the Cascade Range and is part of the Cascade Volcanic Arc, a segment of the Pacific Ring of Fire that includes over 160 active volcanoes. This volcano is well known for its ash explosions and pyroclastic flows.