Post by 1dave on Sept 5, 2020 16:40:26 GMT -7
La Garita Caldera is a large volcanic caldera located in the San Juan volcanic field in the San Juan Mountains near the town of Creede in southwestern Colorado, United States.[1] It lies to the west of the town of La Garita, Colorado. The eruption that created the La Garita Caldera is the largest known explosive eruption in Earth's history.[2]
The La Garita Caldera is one of a number of calderas that formed during a massive ignimbrite flare-up in Colorado, Utah and Nevada from 40–25 million years ago, and was the site of massive eruptions about 26-28 million years ago, during the Oligocene Epoch.
. . .
The scale of La Garita volcanism was the greatest of the Cenozoic Era. The resulting deposit, known as the Fish Canyon Tuff, has a volume of approximately 1,200 cubic miles (5,000 km3), rating it an 8 on the Volcanic Explosivity Index. This is enough material to fill Lake Michigan. By comparison, the May 18, 1980 eruption of Mt. St. Helens was only 0.25 cubic miles (1.0 km3) in volume. The eruption was energetically equivalent to up to 250,000 megatons of TNT
. . .
It is the most energetic event to have taken place on Earth since the Chicxulub impact, which was 400 times more powerful than La Garita.
GEOLOGY:
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 quite large in scale. It is 35 by 75 kilometers (22 by 47 mi) oblong shape . Most supervolcano 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 can be considered a "supervolcano", albeit an extinct one.
La Garita is also the source of at least 7 major eruptions of welded tuff deposits over a time 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 made of dacite that is very similar to that of the Fish Canyon Tuff. This rock, which has characteristics of both lava and welded tuff, was erupted probably shortly before the Fish Canyon Tuff. The lava-like rock has been interpreted as having erupted as thick spatter during low-energy lava fountaining. The lava-like rock is also voluminous — up to 200–300 cubic kilometers (48–72 cu mi).
The La Garita Caldera is one of a number of calderas that formed during a massive ignimbrite flare-up in Colorado, Utah and Nevada from 40–25 million years ago, and was the site of massive eruptions about 26-28 million years ago, during the Oligocene Epoch.
. . .
The scale of La Garita volcanism was the greatest of the Cenozoic Era. The resulting deposit, known as the Fish Canyon Tuff, has a volume of approximately 1,200 cubic miles (5,000 km3), rating it an 8 on the Volcanic Explosivity Index. This is enough material to fill Lake Michigan. By comparison, the May 18, 1980 eruption of Mt. St. Helens was only 0.25 cubic miles (1.0 km3) in volume. The eruption was energetically equivalent to up to 250,000 megatons of TNT
. . .
It is the most energetic event to have taken place on Earth since the Chicxulub impact, which was 400 times more powerful than La Garita.
GEOLOGY:
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 quite large in scale. It is 35 by 75 kilometers (22 by 47 mi) oblong shape . Most supervolcano 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 can be considered a "supervolcano", albeit an extinct one.
La Garita is also the source of at least 7 major eruptions of welded tuff deposits over a time 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 made of dacite that is very similar to that of the Fish Canyon Tuff. This rock, which has characteristics of both lava and welded tuff, was erupted probably shortly before the Fish Canyon Tuff. The lava-like rock has been interpreted as having erupted as thick spatter during low-energy lava fountaining. The lava-like rock is also voluminous — up to 200–300 cubic kilometers (48–72 cu mi).
La Garita Mountains
From Wikipedia, the free encyclopedia
During the Oligocene epoch, a series of caldera building eruptions of titanic proportions, some as large as VEI-8, devastated what is now Colorado and raised up the mountain chain, part of the San Juan Mountains. The La Garita supervolcano's mega-colossal eruption created 5000 km3 of tephra, the largest eruption known. The volcanic hotspot has been dormant for millions of years and is now of no danger to anyone.
Today, they are one of Colorado's lesser known, but more picturesque wilderness areas, the La Garita Wilderness is, in fact, one of the state's original five. "La Garita means "the lookout" in Spanish, and this wilderness amply deserves the name. From the summit of this wilderness's single fourteener (14,014 foot San Luis Peak), climbers can gaze across the upper Rio Grande Valley and down the long stretch of the San Luis Valley. About 35 miles of the Continental Divide lie well above a sprawling forestland that provides ideal habitats for huge numbers of elk and mule deer.[1]
According to the U.S. Geological Survey, the following peaks are part of the La Garita Mountains:[2]
[show]Map all coordinates using OSM
Map up to 200 coordinates using Bing
La Garita Mountains Peak GNIS Feature ID Location
Stewart Peak 190154 38°01′24″N 106°55′24″W
San Luis Peak 190463 37°59′13″N 106°55′53″W
Mesa Mountain 189506 37°54′16″N 106°38′05″W
Pool Table Mountain 189570 37°49′47″N 106°41′31″W
Bowers Peak 189511 37°57′03″N 106°35′22″W
Lookout Mountain 189525 37°59′13″N 106°28′46″W
Lake Mountain 190194 38°00′37″N 106°23′56″W
From Wikipedia, the free encyclopedia
During the Oligocene epoch, a series of caldera building eruptions of titanic proportions, some as large as VEI-8, devastated what is now Colorado and raised up the mountain chain, part of the San Juan Mountains. The La Garita supervolcano's mega-colossal eruption created 5000 km3 of tephra, the largest eruption known. The volcanic hotspot has been dormant for millions of years and is now of no danger to anyone.
Today, they are one of Colorado's lesser known, but more picturesque wilderness areas, the La Garita Wilderness is, in fact, one of the state's original five. "La Garita means "the lookout" in Spanish, and this wilderness amply deserves the name. From the summit of this wilderness's single fourteener (14,014 foot San Luis Peak), climbers can gaze across the upper Rio Grande Valley and down the long stretch of the San Luis Valley. About 35 miles of the Continental Divide lie well above a sprawling forestland that provides ideal habitats for huge numbers of elk and mule deer.[1]
According to the U.S. Geological Survey, the following peaks are part of the La Garita Mountains:[2]
[show]Map all coordinates using OSM
Map up to 200 coordinates using Bing
La Garita Mountains Peak GNIS Feature ID Location
Stewart Peak 190154 38°01′24″N 106°55′24″W
San Luis Peak 190463 37°59′13″N 106°55′53″W
Mesa Mountain 189506 37°54′16″N 106°38′05″W
Pool Table Mountain 189570 37°49′47″N 106°41′31″W
Bowers Peak 189511 37°57′03″N 106°35′22″W
Lookout Mountain 189525 37°59′13″N 106°28′46″W
Lake Mountain 190194 38°00′37″N 106°23′56″W