-
Lake Toba
Lake Toba (Indonesian: Danau Toba) is a lake andsupervolcano.
The lake is 100 kilometres long, 30 kilo-metres wide, and up to 505
metres (1,666 ft) deep. Lo-cated in the middle of the northern part
of the Indonesianisland of Sumatra with a surface elevation of
about 900metres (2,953 ft), the lake stretches from 253N 9831E/
2.88N 98.52E to 221N 9906E / 2.35N 99.1E. Itis the largest lake in
Indonesia and the largest volcaniclake in the world.[1]
Lake Toba is the site of a massive supervolcanic
eruptionestimated at VEI 8 that occurred 69,000 to 77,000
yearsago,[2][3][4] representing a climate-changing event. It isthe
largest known explosive eruption on Earth in the last25 million
years. According to the Toba catastrophe the-ory, it had global
consequences for human populations: itkilled most humans living at
that time and is believed tohave created a population bottleneck in
central east Africaand India, which aects the genetic make up of
the hu-man world-wide population to the present.[5]
It has been accepted that the eruption of Toba led to avolcanic
winter with a worldwide decrease in temperaturebetween 3 to 5 C
(5.4 to 9.0 F), and up to 15 C (27F) in higher latitudes.
Additional studies in LakeMalawiin East Africa show signicant
amounts of ash being de-posited from the Toba eruptions, even at
that great dis-tance, but little indication of a signicant climatic
eectin East Africa.[6]
1 Geology
The Toba caldera complex in Northern Sumatra, com-prises four
overlapping volcanic craters that adjoin theSumatran volcanic
front. The youngest and fourthcaldera is the worlds largest
Quaternary caldera (100by 30 km (62 by 19 mi)) and intersects the
three oldercalderas. An estimated 2,800 km3 (670 cu mi)
ofdense-rock equivalent pyroclastic material, known as theyoungest
Toba tu, was released during one of the largestexplosive volcanic
eruptions in recent geological history.Following this eruption, a
resurgent dome formed withinthe new caldera, joining two half-domes
separated by alongitudinal graben.[3]
At least four cones, four stratovolcanoes, and three cratersare
visible in the lake. The Tandukbenua cone on thenorthwestern edge
of the caldera has only sparse vege-tation, suggesting a young age
of several hundred years.Also, the Pusubukit (Hill Center) volcano
(1971 me-
tres above sea level) on the south edge of the caldera
issolfatarically active and is a Geology Sanctuary.[7][8]
Panoramic view of the town of Ambarita on Samosir,Lake Toba
2 Major eruptionMain article: Toba catastrophe theoryThe Toba
eruption (the Toba event) occurred at what isnow Lake Toba about
67,500 to 75,500 years ago.[9] Itwas the last in a series of at
least three caldera-formingeruptions at this location, with earlier
calderas havingformed around 700,000 and 840,000 years ago.[10]
Thislast eruption had an estimated VEI 8, making it possiblythe
largest explosive volcanic eruption within the last 25million
years.Bill Rose and Craig Chesner of Michigan
TechnologicalUniversity have estimated that the total amount of
mate-rial released in the eruption was about 2,800 km3 (670
cumi)[11]about 2,000 km3 (480 cu mi) of ignimbrite thatowed over
the ground, and approximately 800 km3 (190cu mi) that fell as ash
mostly to the west. The pyroclasticows of the eruption destroyed an
area of 20,000 km2(7,722 sq mi), with ash deposits as thick as 600
m (1,969
1
-
2 3 PEOPLE
Location of Lake Toba shown in red on map.
ft) by the main vent.[11]
The eruption was large enough to have deposited an ashlayer
approximately 15 cm (5.9 in) thick over all of SouthAsia; at one
site in central India, the Toba ash layer to-day is up to 6 m (20
ft) thick[12] and parts of Malaysiawere covered with 9 m (30 ft) of
ash fall.[13] In additionit has been variously calculated that
10,000million tonnes(1.11010 short tons) of sulfurous acid[14] or
6,000 mil-lion tonnes (6.6109 short tons) of sulfur dioxide[15]
wereejected into the atmosphere by the event.The subsequent
collapse formed a caldera that, after ll-ing with water, created
Lake Toba. The island in the cen-ter of the lake is formed by a
resurgent dome.
Landsat photo of Sumatra surrounding Lake Toba
The exact year of the eruption is unknown, but the patternof ash
deposits suggests that it occurred during the north-ern summer
because only the summer monsoon couldhave deposited Toba ashfall in
the South China Sea.[16]The eruption lasted perhaps two weeks, and
the ensuingvolcanic winter resulted in a decrease in average
globaltemperatures by 3.0 to 3.5 C (5 to 6 F) for several
years.Greenland ice cores record a pulse of starkly reduced lev-els
of organic carbon sequestration. Very few plants or
animals in southeast Asia would have survived, and it ispossible
that the eruption caused a planet-wide die-o.Evidence from studies
of mitochondrial DNA suggeststhat humans may have passed through a
genetic bot-tleneck around this time that reduced genetic
diversitybelow what would be expected given the age of thespecies.
According to the Toba catastrophe theory, pro-posed by Stanley H.
Ambrose of the University of Illinoisat Urbana-Champaign in 1998,
the eects of the Tobaeruption may have decreased the size of human
popula-tions to only a few tens of thousands of
individuals.[17]However, this hypothesis is not widely accepted
becausesimilar eects on other animal species have not
beenobserved.[18]
2.1 More recent activity
Since the major eruption ~70,000 years ago, eruptions ofsmaller
magnitude have also occurred at Toba. The smallcone of Pusukbukit
formed on the southwestern marginof the caldera and lava domes. The
most recent erup-tion may have been at Tandukbenua on the
northwest-ern caldera edge, suggested by a lack of vegetation
thatcould be due to an eruption within the last few
hundredyears.[19]
Some parts of the caldera have shown uplift due to par-tial
relling of the magma chamber, for example, pushingSamosir Island
and the Uluan Peninsula above the surfaceof the lake. The lake
sediments on Samosir Island showthat it has risen by at least 450 m
(1,476 ft)[10] since thecataclysmic eruption. Such uplifts are
common in verylarge calderas, apparently due to the upward pressure
ofbelow-ground magma. Toba is probably the largest resur-gent
caldera on Earth. Large earthquakes have recentlyoccurred in the
vicinity of the volcano, notably in 1987along the southern shore of
the lake at a depth of 11 km(6.8 mi).[20] Such earthquakes have
also been recorded in1892, 1916, and 19201922.[10]
Lake Toba lies near the Great Sumatran fault, whichruns along
the centre of Sumatra in the Sumatra FractureZone.[10] The
volcanoes of Sumatra and Java are part ofthe Sunda Arc, a result of
the northeasterly movementof the Indo-Australian Plate, which is
sliding under theeastward-moving Eurasian Plate. The subduction
zone inthis area is very active: the seabed near the west coast
ofSumatra has had several major earthquakes since 1995,including
the 9.1 2004 Indian Ocean Earthquake and the8.7 2005 Sumatra
earthquake, the epicenters of whichwere around 300 km (190 mi) from
Toba.
3 PeopleMost of the people who live around Lake Toba are
ethni-cally Bataks. Traditional Batak houses are noted for
their
-
3distinctive roofs (which curve upwards at each end, as aboats
hull does) and their colorful decor.[21]
4 Flora and faunaThe ora of the lake includes various types
ofphytoplankton, emerged macrophytes, oating macro-phytes, and
submerged macrophytes, while the surround-ing countryside is
rainforest including areas of Sumatrantropical pine forests on the
higher mountainsides.[22]
The fauna includes several species of zooplankton andbenthic
animals. Since the lake is oligotrophic (nutrient-poor), the native
sh fauna is relatively scarce, and theonly endemics areRasbora
tobana (strictly speaking near-endemic, since also found in some
tributary rivers thatrun into the lake)[23] and Neolissochilus
thienemanni, lo-cally known as the Batak sh.[24] The latter species
isthreatened by deforestation (causing siltation),
pollution,changes in water level and the numerous sh species
thathave been introduced to the lake.[24] Other native shesinclude
species such asAplocheilus panchax,Nemacheiluspfeierae, Homaloptera
gymnogaster, Channa gachua,Channa striata, Clarias batrachus,
Barbonymus go-nionotus, Barbonymus schwanenfeldii, Danio
albolin-eatus, Osteochilus vittatus, Puntius binotatus,
Rasborajacobsoni, Tor tambra, Betta imbellis, Betta taeniataand
Monopterus albus.[25] Among the many introducedspecies are Anabas
testudineus, Oreochromis mossam-bicus, Oreochromis niloticus,
Ctenopharyngodon idella,Cyprinus carpio, Osphronemus goramy,
Trichogaster pec-toralis, Trichopodus trichopterus, Poecilia
reticulata andXiphophorus hellerii.[25]
Panoramic view of Parapat from Samosir Island, Lake
Toba.
5 Gallery Lake Toba Aerial View Aerial view of the southern
shore with SibandangIsland visible in the background
View of the lake with an example of Batak architec-ture in the
foreground.
Traditional Batak house at Ambarita, Lake Toba Sipiso-Piso
Waterfall Lake Toba from Tongging Village, near
Sipiso-PisoWaterfall
Lake Toba featured in 1,000-rupiah banknote
6 See also List of lakes in Indonesia List of volcanoes in
Indonesia
7 References[1] Worldlakes.org
[2] Global Volcanism Program page on Toba
[3] Chesner, C.A.; Westgate, J.A.; Rose, W.I.;Drake, R.; Deino,
A. (March 1991). Eruptivehistory of Earths largest Quaternary
caldera(Toba, Indonesia) claried. Geology (Michi-gan Technological
University) 19 (3): 200203.Bibcode:1991Geo....19..200C.
doi:10.1130/0091-7613(1991)0192.3.CO;2. Retrieved2008-08-23.
[4] Ninkovich, D.; N.J. Shackleton, A.A. Abdel-Monem,
J.D.Obradovich, G. Izett (7 December 1978). KAr ageof the late
Pleistocene eruption of Toba, north Sumatra.Nature (Nature
Publishing Group) 276 (276): 574577.Bibcode:1978Natur.276..574N.
doi:10.1038/276574a0.
[5] When humans faced extinction. BBC. 2003-06-09. Re-trieved
2007-01-05.
[6] Lane, Christine S.; Ben T. Chorn; Thomas C. Johnson(29 April
2013). Ash from the Toba supereruption inLake Malawi shows no
volcanic winter in East Africa at75 ka. Proceedings of the National
Academy of Sciences110 (20): 80258029.
Bibcode:2013PNAS..110.8025L.doi:10.1073/pnas.1301474110.
-
4 9 EXTERNAL LINKS
[7] Synonyms and Subfeatures: Toba. Global VolcanismProgram.
Smithsonian Institution. Retrieved December13, 2008.
[8] Gunung Pusukbuhit. March 3, 2013.
[9] Zielinski, G. A.; P.A. Mayewski, L.D. Meeker, S.Whitlow, M.
Twickler and K. Taylor (1996). Poten-tial Atmospheric impact of the
Toba mega-eruption~71,000 years ago. Geophysical Research
Letters(United States: American Geophysical Union) 23(8): 837840.
Bibcode:1996GeoRL..23..837Z.doi:10.1029/96GL00706.
[10] Toba, Sumatra, Indonesia. Oregon State University.]
[11] Supersized eruptions are all the rage!". USGS. April
28,2005.
[12] Acharyya, S.K.; Basu, P.K. (1993). Toba ashon the South
Asia and its implications for correla-tion of late pleistocene
alluvium. Quaternary Re-search 40 (1): 1019.
Bibcode:1993QuRes..40...10A.doi:10.1006/qres.1993.1051.
[13] Scrivenor, John Brooke (1931). The Geology of
Malaya.London: MacMillan. OCLC 3575130., noted by Weber.
[14] Huang, C.Y.; Zhao, M.X.; Wang, C.C.; Wei, G.J.(2001).
Cooling of the South China Sea by theToba Eruption and correlation
with other climate prox-ies 71,000 years ago. Geophysical Research
Letters28 (20): 39153918.
Bibcode:2001GeoRL..28.3915H.doi:10.1029/2000GL006113.
[15] Robock, A.; C.M. Ammann; L. Oman; D. Shin-dell; S. Levis;
G. Stenchikov (2009). Did the Tobavolcanic eruption of ~74k BP
produce widespreadglaciation?". Journal of Geophysical Research114:
D10107. Bibcode:2009JGRD..11410107R.doi:10.1029/2008JD011652.
[16] Bhring, C.; Sarnthein, M.; Leg 184 Shipboard ScienticParty
(2000). Toba ash layers in the South China Sea:evidence of
contrasting wind directions during eruptionca. 74 ka.. Geology 28
(3): 275278. doi:10.1130/0091-7613(2000)0282.3.CO;2.
[17] Yellowstone Is a Supervolcano?". Biot Reports (Subur-ban
Emergency Management Project) (164). January 11,2005. Retrieved
2008-02-21.
[18] Gathorne-Hardy, F. J., and Harcourt-Smith, W. E. H.,The
super-eruption of Toba, did it cause a human bottle-neck?", Journal
of Human Evolution 45 (2003) 227230.
[19] Toba volcano (Indonesia, Sumatra)".
VolcanoDiscov-ery.com.
[20] Signicant Earthquakes of theWorld. United States
Ge-ological Survey (USGS).
[21] Batak People. IndonesianMusic.com.
[22] Danau Toba (Lake Toba)". International Lake Environ-ment
Committee.
[23] Lumbantobing, D. N. (2010). Four New Species of theRasbora
trifasciata-Group (Teleostei: Cyprinidae) fromNorthwestern Sumatra,
Indonesia. Copeia 4: 644-670
[24] Saragih, B., and S. Sunito (2001). Lake Toba: Need foran
integrated management system. Lakes & Reservoirs:Research &
Management 6(3): 247251.
[25] FishBase (2012). Species in Toba. Accessed 25
January2012
8 Additional reading Rampino, Michael R. and Stephen Self
(1993).Climate-volcanism feedback and the Toba erup-tion of 74,000
Years Ago. Quaternary Research40 (3): 269280.
Bibcode:1993QuRes..40..269R.doi:10.1006/qres.1993.1081.
Vazquez, Jorge A. and Mary R. Reid (2004).Probing the
accumulation history of the vo-luminous Toba Magma. Science 305
(5686):991994.
Bibcode:2004Sci...305..991V.doi:10.1126/science.1096994. PMID
15310899.
Petraglia, M. et al. (2007). Middle PaleolithicAssemblages from
the Indian Subcontinent Beforeand After the Toba Super-Eruption.
Science 317(5834): 114116.
Bibcode:2007Sci...317..114P.doi:10.1126/science.1141564. PMID
17615356.
9 External links Toba, Sumatra, Indonesia Volcano.umd.edu
Ac-cessed 11 December 2005
Stanley H. Ambrose, Volcanic Winter, and Dieren-tiation of
Modern Humans Accessed 11 December2005
Joel Achenbach, Who Knew, National GeographicAccessed 11
December 2005
(Lake Toba Ecosystem Management Plan) Fromlaketoba.org
Lake Toba travel guide from Wikivoyage
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