Mount Okmok
| Mount Okmok | ||
|---|---|---|
 Aerial view of the Okmok Caldera |
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| height | 1073 m | |
| location | Umnak , Aleutian Islands , Alaska , USA | |
| Mountains | Aleutian chain | |
| Coordinates | 53 ° 28 '5 " N , 168 ° 10' 30" W | |
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| Type | Shield volcano , caldera | |
| rock | Tertiary volcanic rock | |
| Last eruption | 2008 | |
The Mount Okmok is the highest point of the edge of Okmok Caldera on the northeastern part of Umnak in the eastern Aleutian Islands in Alaska .
The circular caldera with a diameter of 9.5 kilometers is located on a large shield volcano with a diameter of 35 kilometers. A large crater lake 150 meters deep once filled the 12,000-year-old caldera, but was drained through a notch eroded into the northeastern rim. Today there is only a small remaining lake with a diameter of 300 meters in the western part of the flat caldera floor. There are hot springs and fumaroles in the caldera . Numerous secondary cones and lava domes, one of them the 1253 meter high Mount Tulik , are located on the flanks of the mountain all the way down to the coast.
The formation of the volcano began in the late Tertiary or early Quaternary . Huge pyroclastic eruptions resulted in two overlapping calderas. The older one was formed about 8200 years ago, the younger one about 2400 years ago.
The eruption at the beginning of 43 BC BC was one of the strongest volcanic eruptions of the last 2500 years and had an impact on the climate worldwide. The years 43 and 42 BC Are among the coldest in this period. In the Mediterranean region , temperatures were loud model calculations from the year 2020 to an average of three degrees Celsius and possibly up to seven degrees Celsius below average. It was also unusually humid, which led to crop failures and famine. In Egypt the annual summer flood of the Nile was completely absent; the Nile brought no fertile mud to the fields. This had a devastating effect on the grain harvest. Historical sources report food shortages and famine, which is why Queen Cleopatra VII did not supply the civil war parties with grain.
Mount Okmok erupted 14 times between 1805 and 1988. The Aleutian village near Cape Tanak was destroyed in the eruption of 1817 .
On July 12, 2008, an explosive eruption began without warning, the eruption column of which reached a height of about 15 kilometers. The Alaska Volcano Observatory issued a warning. The eruptions lasted about five weeks and were classified as VEI 4 .
Web links
- Mount Okmok in the Global Volcanism Program of the Smithsonian Institution (English)
- Alaska Volcano Observatory (English)
- Outbreak in July / August 2008 (English)
See also
Individual evidence
- Jump up ↑ Joseph R. McConnell, Michael Sigl, Gill Plunkett, et al .: Extreme climate after massive eruption of Alaska's Okmok volcano in 43 BCE and effects on the late Roman Republic and Ptolemaic Kingdom. In: Proceedings of the National Academy of Sciences of the United States of America , 2020, doi : 10.1073 / pnas.2002722117
- ↑ science.orf.at: Vulkan shook the Roman Republic (report on the above-mentioned study by Joseph R. McConnell)
- ↑ see timeline on avo.alaska.edu
- ↑ Eruption of 1817 (English)
- ↑ Okmok Volcano Activity Notifications . Alaska Volcano Observatory. July 13, 2008. Retrieved July 13, 2008.