La Garita Caldera
This article includes a list of general references, but it lacks sufficient corresponding inline citations. (March 2013) |
La Garita Caldera | |
---|---|
Highest point | |
Coordinates | 37°45′23″N 106°56′03″W / 37.75639°N 106.93417°W |
Geography | |
Location | Mineral County, Colorado, US, around Creede |
Parent range | San Juan Mountains |
Geology | |
Mountain type | Caldera, extinct supervolcano |
Last eruption | 26.3 Ma (Fish Canyon Tuff 27.8 Ma) |
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.[1] 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.[2][3]
Date
The La Garita Caldera is one of a number of calderas that formed during a massive
Area devastated
The area devastated by the La Garita eruption is thought to have covered a significant portion of what is now Colorado. The deposit, known as the Fish Canyon Tuff, covered at least 11,000 sq mi (28,000 km2). Its average thickness is 330 ft (100 m). The eruption might have formed a large-area ash-fall, but none has yet been identified.[5]
Size of eruption
The scale of La Garita volcanism was the second greatest of the
The Fish Canyon eruption was the second most energetic event to have occurred on Earth since the
Geology
This section needs additional citations for verification. (February 2017) |
The Fish Canyon Tuff, made of dacite, is uniform in its petrological composition and forms a single cooling unit despite the huge volume. Dacite is a silicic volcanic rock common in explosive eruptions, lava domes and short thick lava flows. There are also large intracaldera lavas composed of andesite, a volcanic rock compositionally intermediate between basalt (poor in silica content) and dacite (higher silica content) in the La Garita Caldera.
The caldera itself, like the eruption of Fish Canyon Tuff, is large in scale. It is 22 by 47 miles (35 by 75 km) and oblong in shape. Many calderas of explosive origin are slightly ovoid or oblong in shape. Because of the vast scale and erosion, it took scientists over 30 years to fully determine the size of the caldera. La Garita is considered an
La Garita is also the source of at least seven major eruptions of welded tuff deposits over a span of 1.5 million years since the Fish Canyon Tuff eruption. The caldera is also known to have extensive outcrops of a very unusual lava-like rock unit, called the Pagosa Peak Dacite, made of dacite that is very similar to that of the Fish Canyon Tuff. The Pagosa Peak Dacite, which has characteristics of both lava and welded tuff, was likely erupted shortly before the Fish Canyon Tuff. The Pagosa Peak Dacite has been interpreted as having erupted during low-energy pyroclastic fountaining and has a volume of about 50–70 cubic miles (200–300 km3). These rocks were identified as lava because the unit has a highly elongated shape (1:50) and very high viscosity of the crystal-rich magma similar to those of flow-layered silicic lava. The Pagosa Peak Dacite formed by low-column pyroclastic fountaining and lateral transport as dense, poorly-inflated pyroclastic flows.[10]
See also
References
- ^ Steven, Thomas A.; Lipman, Peter W. (1976). "Calderas of the San Juan Volcanic Field, Southwestern Colorado". U.S. Geological Survey Professional Papers. 958. Washington, DC: U.S. Government Printing Office: 1–35. Retrieved 2012-05-16.
- ^ "What's the Biggest Volcanic Eruption Ever?". livescience.com. November 10, 2010. Retrieved 2014-02-01.
- .
- .
- ISBN 0-8137-2346-9.)
{{cite journal}}
: CS1 maint: numeric names: authors list (link - ^ Super Volcano: The Ticking Time Bomb Beneath Yellowstone National Park. Voyageur Press. 10 November 2007.
- ^ Mason, et al.
- ^ "La Garita Mountains grew from volcanic explosions 35 million years ago". US Forest Service. 2021-08-25. Retrieved 2022-04-23.
- ISSN 0036-8075.
- .
Bibliography
- Lipman, Peter W.; Robinson, Joel E.; Dutton, Dillon R.; Ramsey, David W.; Felger, Tracey J. (2006). Geologic Map of the Central San Juan Caldera Cluster, Southwestern Colorado. USGS Geologic Investigations Series I-2799. (includes maps, photo collection, and links to on-line abstracts)
- Mason, Ben G.; Pyle, David M.; Oppenheimer, Clive (2004). "The size and frequency of the largest explosive eruptions on Earth". Bulletin of Volcanology. 66 (8): 735–748. S2CID 129680497.
- Askren, Daniel R.; Rodden, Michael F.; Whitney, James A. (1997). "Petrogenesis of Tertiary Andesite Lava Flows Interlayered with Large-Volume FelsicAsh-Flow Tuffs of the Western USA". Journal of Petrology. 38 (8): 1021–1046. .
- Largest explosive eruptions: New results for the 27.8 Ma Fish Canyon Tuff and the La Garita caldera, San Juan volcanic field, Colorado
- The Mid-Tertiary Ignimbrite Flare-Up
External links
- USGS Hawaiian Volcano Observatory: Supersized eruptions are all the rage!
- Maps:
- Robinson, Joel E.; Dutton, Dillon R.; Ramsey, David W.; Lipman, Peter W.; Felger, Tracey J. (2006). Geologic Map of the Central San Juan Caldera Cluster, Southwestern Colorado: Geologic Investigations Series. Vol. I-2799. U.S. Geological Survey. Retrieved 2010-05-03.
- "Central Colorado Volcanic field". Journal of Petrology. Archived from the original on 2013-07-08. Retrieved 2010-03-16.
- "Central Colorado Volcanic field". Dr. Matthew E. Brueseke, Department of Geology, Kansas State University. Archived from the original on 2011-07-19. Retrieved 2010-03-26.