Lo'ihi

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Lo'ihi
Map of the Lōʻihi off the island of Hawaii

Map of the Lōʻihi off the island of Hawaii

height 975 m below sea level
location southeast of the island of Hawaii
Coordinates 18 ° 55 '12 "  N , 155 ° 16' 12"  W Coordinates: 18 ° 55 '12 "  N , 155 ° 16' 12"  W.
Lōʻihi (Hawaii)
Lo'ihi
Type submarine volcano
Last eruption July 16 - August 9, 1996

Lōʻihi (also Lo'ihi, Loihi ) is an undersea volcano 35 kilometers south of Hawaii . The height from the bottom of the Pacific Ocean to the summit is approx. 3000 meters, to the surface of the sea 975 meters are still missing.

Near the top of Lōʻihi there is an underwater automatic observatory that has already acoustically observed an eruption . A copper and fiber optic cable connects the observatory with the opposite station at Whittington Beach Park in southern Hawaii.

geology

The Lōʻihi is a deep-sea mountain or submarine volcano that is located on the slope of Mauna Loa , the largest shield volcano on earth. It is the youngest volcano formed by the hotspot under Hawaii and belongs to the elongated Imperator Ridge . The distance between the summit of the older Mauna Loa and the summit of Lōʻihi is about 80 km and thus roughly corresponds to the diameter of the Hawaiian hotspot. The Lōʻihi consists of a summit with three shaft craters , an 11 km long fault zone , which extends from the summit in north-south direction, and a 19 km long fault zone, which runs from the summit to south-southeast.

The shaft craters are named West Crater (English 'West Pit'), East Crater (English 'East Pit') and Peles Crater (English 'Pele's Pit'). Peles Crater is the youngest of the three and is located in the southern area of ​​the summit. Its walls are 200 m high and were formed in July 1996, when the hydrothermal field Peles Vent - the formation that was previously in its place - collapsed. With a thickness of 20 m, the walls of Peles Crater are unusually thick for a Hawaiian volcano and suggest that the craters have filled with lava several times in the past.

Map with the topography of a north-south ridge, which has a course slightly east of the south direction. The arrow drawn points to Pele's Pit. Pele's Pit is about 1000 meters below the sea surface; to the south, the ridge sinks about 3500 meters to the ocean floor.
Bathymetric map of Lōʻihi (arrow points to Peles crater).

The fault zones of the Lōʻihi running from north to south give the volcano the characteristic, elongated shape from which its name ( Hawaiian : 'long') is derived. The northern fault zone consists of a longer western part and a shorter eastern part. Investigations have shown that both the northern and southern faults have no sedimentary cover. This suggests that there has been volcanic activity there in the recent past. A bulge in the western part of the northern fault zone has three 60 to 80 m high, conical elevations.

Until 1970 the Lōʻihi was thought to be an inactive volcano that had reached its current location due to the ocean floor spreading . The ocean floor under Hawaii is 80 to 100 million years old and formed on the East Pacific Ridge , a divergence zone where the drifting apart of tectonic plates and magma rising from the Earth's mantle creates a new sea floor. This newly formed earth crust is slowly moving away from the divergence zone. The ocean floor under Hawaii migrated over a period of 80 to 100 million years from the East Pacific Ridge 6,000 km to the west, moving the ancient deep sea mountains with it. When scientists examined a series of earthquakes in Hawaii in 1970, however, they found that the Lōʻihi is an active volcano on the Emperor's Ridge. The age structure of the craters at its summit confirms that the Lōʻihi is slowly moving eastward due to volcanic activity and away from its place of origin above the Hawaiian hotspot.

3D map of the Lōʻihi
3D map of the deep sea mountain

Measured from the sea floor, the Lōʻihi has a height of more than 3000 m, but its summit is still 975 m below the water surface. The Lōʻihi has a slope of about five degrees. Its northern foot begins about 1900 m below sea level on the slope of Mauna Loa, while the south side sits on the sea floor and is much lower at 4755 m below sea level. Measured from the north side, its summit is 931 m above the sea floor, but measured from the south side, the volcano reaches a height of 3786 m above the sea floor.

The Lōʻihi follows the development pattern typical of Hawaiian volcanoes. Geochemical analyzes of its lava show that the Lōʻihi is currently in the transition phase from the pre-shield stage to the shield volcano and provides us with valuable information about the early development of Hawaiian volcanoes. In the pre-shield stage, these volcanoes have steeper slopes, low levels of activity, and produce alkaline basaltic lava . Due to further volcanic activity, the Lōʻihi will eventually form an island. The growth of the volcano has destabilized its side slopes. This is why landslides are common and a large part of the steep south-east slope is covered with rubble . Similar deposits on other Hawaiian volcanoes show that such debris from landslides is typical of the early development of a Hawaiian volcano. It is expected that the Lōʻihi will rise above sea level in 10,000 to 100,000 years.

Age and growth

With the help of radiometric dating , the age of rock samples from the Lōʻihi was determined. The Hawaiian Center for Volcanology Hawaii Center for Volcanology] examined rock samples collected from various expeditions. The expedition carried out in 1978 is of particular importance, from which 17 samples were taken with a dredger. Most of the samples turned out to be old: the oldest rock is dated to around 300,000 years. Some young breccias were also collected after the 1996 seismic activity . Based on the rock samples, scientists estimate the age of the Lōʻihi to be around 400,000 years. Some samples from the active east side of the volcano have been dated from 4,000 to 21,000 years ago, but these dates are not considered reliable. At the foot of the volcano, an average of 3.5 mm of new rock forms per year and 7.8 mm per year near the summit. If the data model from other volcanoes, such as Kilauea , can be transferred to the Lōʻihi, it can be assumed that 40% of the volcanic mass has formed during the last 100,000 years. Assuming linear growth, the Lōʻihi would be 250,000 years old. However, since the activity of the lōʻihi has increased over time, as is typical of hotspot volcanoes, it takes at least 400,000 years for a volcano of this type to reach the mass of the lōʻihi. The Hawaiian volcanoes move north-west at a speed of about 10 cm per year. This means that the Lōʻihi was 40 km southeast of its current location when it first erupted.

See also

Web links

Individual evidence

  1. ^ Loihi Volcano , School of Ocean and Earth Science and Technology, University of Hawaiʻi at Mānoa
  2. ^ A b Lōʻihi Seamount Hawaiʻi's Youngest Submarine Volcano . In: Hawaiian Volcano Observatory . United States Geological Survey . Retrieved March 1, 2009.
  3. ↑ Alexander Malahoff: Geology of the summit of Lōʻihi submarine volcano . In: Decker, Robert W. Wright, Thomas L. Stauffer, Peter H. (Eds.): Volcanism in Hawaiʻi: US Geological Survey Professional Paper 1350  (= United States Geological Survey Professional Paper 1350), Volume 1. United States Government Printing Office , Washington 1987, pp. 133-44 (accessed June 15, 2009).
  4. ↑ Alexander Malahoff, Irina Ya. Kolotyrkina, Brian P. Midson and Gary J. Massoth: A decade of exploring a submarine intraplate volcano: Hydrothermal manganese and iron at Lō'ihi volcano, Hawaiʻi . In: American Geophysical Union and Geochemical Society (eds.): G³: Geochemistry, Geophysics, Geosystems . 7, No. 6, January 6, 2006, ISSN  1525-2027 . doi : 10.1029 / 2005GC001222 . Retrieved November 6, 2009.
  5. ↑ Alexander Malahoff: Lōʻihi Submarine Volcano: A unique, natural extremophile laboratory . In: In the Spotlight . Office of Oceanic and Atmospheric Research ( NOAA ). December 18, 2000. Archived from the original on February 16, 2009. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved March 1, 2009. @1@ 2Template: Webachiv / IABot / www.oar.noaa.gov
  6. ↑ a b , Fornari, DJ, Garcia, MO, Tyce, RC, Gallo, DG Morphology and structure of Loihi seamount based on seabeam sonar mapping . In: Journal of Geophysics Research . 93, No. 15, 1988, pp. 227-38. Retrieved June 14, 2009.
  7. ↑ Loʻihi , meaning "length, height, distance, long". See: Mary Kawena Pukui, Samuel Hoyt Elbert: Hawaiian dictionary: Hawaiian-English, English-Hawaiian . University of Hawaii Press, 1986, ISBN 0-8248-0703-0 , p. 209 ; lōʻihi in Hawaiian Dictionaries
  8. ↑ a b Ken Rubin: General Information About Loihi . In: Hawaii Center for Volcanology . School of Ocean and Earth Science and Technology, University of Hawaiʻi at Mānoa . January 19, 2006. Retrieved February 1, 2009.
  9. ↑ a b Loihi . In: Global Volcanism Program . Smithsonian Institution. Retrieved March 1, 2009.
  10. ↑ a b Myron G. Best: Igneous and Metamorphic Petrology . Wiley, John & Sons, Incorporated, 1991, ISBN 978-1-4051-0588-0 , p. 359.
  11. ^ Evolution of Hawaiian Volcanoes . In: USGS Site . USGS. September 8, 1995. Retrieved March 7, 2009.
  12. ↑ a b Michael O. Garcia, Jackie Caplan-Auerbach, Eric H. De Carlo, MD Kurz, N. Becker: Geology, geochemistry and earthquake history of Lōʻihi Seamount, Hawaiʻi (author's version of the article published in 2006) Archived from the original on 18. July 2011. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. ( PDF ) In: School of Ocean and Earth Science and Technology, University of Hawaiʻi at Mānoa (Hrsg.): Chemie der Erde - Geochemistry . 66, No. 2, September 20, 2005, pp. 81-108. Retrieved March 20, 2009. @1@ 2Template: Webachiv / IABot / darchive.mblwhoilibrary.org
  13. ↑ Michael O. Garcia, David G. Grooms, John J. Naughton: Petrology and geochronology of volcanic rocks from seamounts along and near the Hawaiian Ridge: Implications for propagation rate of the ridge . In: The Geological Society of America (Ed.): Lithosphere . No. 20, July 1987, pp. 323-336. doi : 10.1016 / S0024-4937 (87) 80005-1 . Retrieved September 25, 2017.