A caldera is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the structural integrity of such a chamber, greatly diminishing its capacity to support its own roof, and any substrate or rock resting above. The ground surface then collapses into the emptied or partially emptied magma chamber, leaving a large depression at the surface. Although sometimes described as a crater, the feature is actually a type of sinkhole, as it is formed through subsidence and collapse rather than an explosion or impact. Compared to the thousands of volcanic eruptions that occur over the course of a century, the formation of a caldera is a rare event, occurring only a few times within a given window of 100 years. Only seven caldera-forming collapses are known to have occurred between 1911 and 2016. More recently, a caldera collapse occurred at Kīlauea, Hawaii in 2018.
The San Juan Mountains is a high and rugged mountain range in the Rocky Mountains in southwestern Colorado and northwestern New Mexico. The area is highly mineralized and figured in the gold and silver mining industry of early Colorado. Major towns, all old mining camps, include Creede, Lake City, Silverton, Ouray, and Telluride. Large scale mining has ended in the region, although independent prospectors still work claims throughout the range. The last large-scale mines were the Sunnyside Mine near Silverton, which operated until late in the 20th century, and the Idarado Mine on Red Mountain Pass, which closed in the 1970s. Famous old San Juan mines include the Camp Bird and Smuggler Union mines, both located between Telluride and Ouray.
Long Valley Caldera is a depression in eastern California that is adjacent to Mammoth Mountain. The valley is one of the Earth's largest calderas, measuring about 20 mi (32 km) long (east-west), 11 mi (18 km) wide (north-south), and up to 3,000 ft (910 m) deep.
The Mono–Inyo Craters are a volcanic chain of craters, domes and lava flows in Mono County, Eastern California. The chain stretches 25 miles (40 km) from the northwest shore of Mono Lake to the south of Mammoth Mountain. The Mono Lake Volcanic Field forms the northernmost part of the chain and consists of two volcanic islands in the lake and one cinder cone volcano on its northwest shore. Most of the Mono Craters, which make up the bulk of the northern part of the Mono–Inyo chain, are phreatic volcanoes that have since been either plugged or over-topped by rhyolite domes and lava flows. The Inyo volcanic chain form much of the southern part of the chain and consist of phreatic explosion pits, and rhyolitic lava flows and domes. The southernmost part of the chain consists of fumaroles and explosion pits on Mammoth Mountain and a set of cinder cones south of the mountain; the latter are called the Red Cones.
Newberry Volcano is a large active shield-shaped stratovolcano located about 20 miles (32 km) south of Bend, Oregon, United States, 35 miles (56 km) east of the major crest of the Cascade Range, within the Newberry National Volcanic Monument. Its highest point is Paulina Peak. The largest volcano in the Cascade Volcanic Arc, Newberry has an area of 1,200 square miles (3,100 km2) when its lava flows are taken into account. From north to south, the volcano has a length of 75 miles (121 km), with a width of 27 miles (43 km) and a total volume of approximately 120 cubic miles (500 km3). It was named for the geologist and surgeon John Strong Newberry, who explored central Oregon for the Pacific Railroad Surveys in 1855.
Mount Mazama is a complex volcano in the western U.S. state of Oregon, in a segment of the Cascade Volcanic Arc and Cascade Range. Most of the mountain collapsed following a major eruption approximately 7,700 years ago. The volcano is in Klamath County, in the southern Cascades, 60 miles (97 km) north of the Oregon–California border. Its collapse, due to the eruption of magma emptying the underlying magma chamber, formed a caldera that holds Crater Lake. Mount Mazama originally had an elevation of 12,000 feet (3,700 m), but following its climactic eruption this was reduced to 8,157 feet (2,486 m). Crater Lake is 1,943 feet (592 m) deep, the deepest freshwater body in the U.S. and the second deepest in North America after Great Slave Lake in Canada.
The Powderhorn Wilderness is a 62,050-acre (251.1 km2) wilderness area in Hinsdale and Gunnison counties, Colorado, United States, located 5 miles (8.0 km) northeast of Lake City.
La Garita Caldera is a large caldera and extinct supervolcano in the San Juan volcanic field in the San Juan Mountains around the town of Creede in southwestern Colorado, United States. It is west of La Garita, Colorado. The eruption that created the La Garita Caldera is among the largest known volcanic eruptions in Earth's history, as well as being one of the most powerful known supervolcanic events.
The Wheeler Geologic Area is a highly eroded outcropping of layers of volcanic ash, located in the San Juan Mountains in southern Colorado, United States. It is about 10 miles east north-east of Creede. The ash is the result of eruptions from the La Garita Caldera approximately 25 million years ago.
The La Garita Mountains are a high mountain range in the San Juan Mountains, a sub-range of the Southern Rocky Mountains. The mountains are located in Saguache and Mineral counties in southwestern Colorado and are almost entirely managed as public land within the Rio Grande National Forest.
The La Garita Wilderness is a U.S. Wilderness Area located in the La Garita Mountains of southern Colorado. The 129,626-acre (524.58 km2) wilderness established in 1964 in Gunnison and Rio Grande National Forests includes segments of the Colorado Trail and the Continental Divide Trail. At 14,014 feet (4,271 m), San Luis Peak is the highest point in the wilderness area.
This timeline of volcanism on Earth includes a list of major volcanic eruptions of approximately at least magnitude 6 on the Volcanic explosivity index (VEI) or equivalent sulfur dioxide emission during the Quaternary period. Other volcanic eruptions are also listed.
The San Juan volcanic field is part of the San Juan Mountains in southwestern Colorado. It consists mainly of volcanic rocks that form the largest remnant of a major composite volcanic field that covered most of the southern Rocky Mountains in the Middle Tertiary geologic time. There are approximately fifteen calderas known in the San Juan Volcanic Fields; however, it is possible that there are two or even three more in the region.
Cochetopa Creek is a stream in Saguache and Gunnison counties in Colorado, United States. It rises on San Luis Peak in the La Garita Mountains. It merges with Tomichi Creek near the town of Parlin, Colorado, along Highway 50.
Cochetopa Dome is a mountain in the San Juan Mountains, in Saguache County, Colorado. The 11,138 ft (3,395 m) mountain is located in the Gunnison National Forest. With a prominence of 1,752 feet (534 m), Cochetopa Dome is the 110th most prominent summit in the state of Colorado.
Carnero Pass is a mountain pass in Saguache County of south-central Colorado. It is located in the La Garita Mountains, a sub-range of the San Juan Mountains, and divides the waters of Houselog Creek to the north and Carnero Creek to the south. Carnero Pass is traversed by County Road 41G.
Tomichi Pass is a high mountain pass in the Sawatch Range of the Rocky Mountains of Colorado. It is located in Gunnison County and in the Gunnison National Forest. The pass divides the watersheds of Middle Quartz Creek to the north and Tomichi Creek to the south.
Los Pinos Pass is a mountain pass in Saguache County of south-central Colorado. It is located in the northern San Juan Mountains, a sub-range of the Rocky Mountains, and divides the waters of Cebolla Creek to the west and Los Pinos Creek to the east. Los Pinos Pass is traversed by Forest Road 788.
Chipeta Mountain is a mountain summit in the Sawatch Range of the Rocky Mountains of North America. The 13,472-foot (4,106 m) mountain is located in Chaffee County, Colorado, and in the San Isabel National Forest.
