Humphrey's Peak is the point of the range at 12,633 feet high. (Credit: Brugger-Schorr, Carrie. Hiking. EMBED. Yup, the San Francisco Peaks are an extinct stratovolcano which last erupted some 200,000 years ago. San Francisco Mountain is a composite volcano comprising layers of weak, unconsolidated of volcanic tephra (ash, lapilli and bombs) alternating with competent, dense lava flows. Eruptions built the peak between 1 million and 400,000 years ago. remove-circle Share or Embed This Item. The San Francisco Peaks north of Flagstaff are Arizona's highest mountain but used to be much higher before the stratovolcano collapsed. Volcanic activity in the San Francisco Peaks began about 1.3 million years ago and ended about 100,000 years ago; making it the longest lived volcanic center in the field. Hazards from future eruptions would have local impacts. Public domain.) The breathtaking beauty of the San Francisco Peaks has been, and continues to be, molded by the forces of nature. San Francisco Peaks, three summits— Humphreys, Agassiz, and Fremont peaks—on the rim of an eroded extinct volcano 10 miles (16 km) north of Flagstaff on the Colorado Plateau in north-central Arizona, U.S. Humphreys Peak (12,633 feet [3,851 metres]) is the state’s highest point, and from it places The gentle slopes at far right and far left project upward toward the center, giving an idea of how high this mountain used to be, … The Coconino National Forest surrounds the mountain. San Francisco Peaks: Extinct volcano fun - See 251 traveler reviews, 73 candid photos, and great deals for Flagstaff, AZ, at Tripadvisor. San Francisco Peaks in the San Francisco Volcanic Field are located outside of Flagstaff Arizona. San Francisco Peaks located in Flagstaff, Arizona are a volcanic mountain range. A large portion of the water supply for Flagstaff, Arizona is found in the mountain. The San Francisco volcanic field is an area of volcanoes in northern Arizona, north of Flagstaff, US.The field covers 1,800 square miles (4,700 km²) of the southern boundary of the Colorado Plateau.The field contains 600 volcanoes ranging in age from nearly 6 million years old to less than 1,000 years (Miocene to Holocene), of which Sunset Crater is the youngest. The San Francisco volcanic field is a vast area covering more than 10,000 km22 containing cinder cones, lava fields, lava domes and the majestic (extinct) San Francisco Peaks, the highest of all mountains in Arizona, rising 5,000 feet above the surrounding plateau. The Peaks are what remains of a stratovolcano that was eroded. arizona_volcanoes.AST20031021_lrg.jpg . The San Francisco Volcanic Field covers 1,800 square mile in northern Arizona with volcanoes that are up to 6 million years old. The San Francisco Peaks range, also called San Francisco Mountain, was once a huge, cone-shaped stratovolcano that rose somewhere between 16,000 and 20,000 feet high and looked like Mount Rainier in Washington or Mount Fuji in Japan. Despite the extinct volcanoes, Arizona is actually home to a prominent volcanic field that is still active! San Francisco Peaks Volcano Field: Image of the Day Item Preview arizona_volcanoes.AST20031021.jpg . The remnants of a dormant volcano, the peaks are home to some of the most spectacular hikes in the state, including a trail that leads you to the summit of Humphreys Peak, with an elevation of 12,633 feet.