Mount Spurr
Mount Spurr is a stratovolcano
A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...

 in the Aleutian Volcanic Arc of Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

, named after United States Geological Survey
United States Geological Survey
The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...

 geologist and explorer Josiah Edward Spurr
Josiah Edward Spurr
Josiah Edward Spurr was an American geologist, explorer, and author.He led the first United States Geological Survey expedition to map and chart the interior regions of Alaska, starting with the Yukon Territory in 1896 and continuing with the Kuskokwim River region in 1898. His books were seen as...

, who led an expedition to the area in 1898. The Alaska Volcano Observatory
Alaska Volcano Observatory
The Alaska Volcano Observatory is a joint program of the United States Geological Survey, the Geophysical Institute of the University of Alaska Fairbanks, and the State of Alaska Division of Geological and Geophysical Surveys...

 (AVO) currently rates Mount Spurr as Level of Concern Color Code Green.

Mount Spurr, the highest volcano of the Aleutain arc, is a large lava dome constructed at the center of a roughly 5 km-wide horseshoe-shaped caldera that is open to the south.