Mount Tambora is an active stratovolcano and the highest mountain on the island of Sumbawa in Indonesia. Sumbawa is flanked to the north and south by colliding oceanic crust in an active subduction zone that created the mountain. The elevation of Mount Tambora was around 4,300 metres (14,100 ft) in the 18th century, making it one of the tallest peaks in the Indonesian archipelago at that time.
After a large magma chamber inside the mountain filled, volcanic activity reached a climax with the catastrophic eruption of 10 April 1815. This eruption had a volcanic explosivity index (VEI) of 7, the only unambiguously confirmed VEI-7 eruption since the Lake Taupo eruption in about 180 AD. The ejecta volume was an estimated 160 cubic kilometres (38 cu mi), making this the largest volcanic eruption in recorded history. The explosion was heard on Sumatra, more than 2,000 kilometres (1,200 mi) away. Heavy volcanic ash falls were observed as far away as Borneo, Sulawesi, Java, and the Maluku Islands. The human death toll was at least 71,000, with the eruption itself killing 11,000-12,000. Starvation and disease caused most of the deaths, as the fallout ruined agricultural production in the region. The often-cited death toll of 92,000 is believed to be too high. The eruption also caused global climate anomalies, including a "volcanic winter" phenomenon. 1816 has become known as the "Year Without a Summer" because of the eruption's effect on North American and European weather. Crops failed and livestock died in much of the Northern Hemisphere, triggering the worst famine of the 19th century.
During an excavation in 2004, archaeologists discovered cultural remains buried by the 1815 eruption. The artefacts were preserved in their 1815 positions at the site.
Video Mount Tambora
Geographical setting
Mount Tambora is on Sumbawa Island, which is part of the Lesser Sunda Islands. They are a segment of the Sunda Arc, a string of volcanic islands in the southern chain of the Indonesian archipelago. Mount Tambora is on Sumbawa Island's Sanggar peninsula. To the north of the peninsula is the Flores Sea and to the south is Saleh Bay, which is 86 kilometres (53 mi) long and 36 kilometres (22 mi) wide. At the mouth of this bay is a 30,000-hectare islet called Moyo (or Pulau Moyo in Indonesian), which has a luxury resort.
Mount Tambora is of interest to seismologists, volcanologists, archaeologists, and biologists. It also attracts tourists for hiking and wildlife-viewing. The nearest cities are Dompu and Bima. Three concentrations of villages are around the mountain slope. To the east is Sanggar village, to the north-west are Doro Peti and Pesanggrahan villages, and to the west is Calabai village.
Three ascent routes are used to reach the caldera. The first route starts from Doro Mboha village south of the mountain and follows a paved road through a cashew plantation until it reaches 1,150 metres (3,770 ft). The end of this route is the southern part of the caldera at 1,950 metres (6,400 ft), reachable by a hiking track. This location is usually used as a base camp to monitor volcanic activity because it takes only one hour to reach the caldera. The second route is south-west of the mountain, starting from Doro Peti village, the location of the volcanic monitoring station. The third route starts from Pancasila village north-west of the mountain and passes through a coffee plantation. Using the third route, the caldera is accessible only on foot.
Maps Mount Tambora
Geological history
Formation
Mount Tambora formed around 57,000 years ago. It is 340 kilometres (210 mi) north of the Java Trench system and 180-190 kilometres (110-120 mi) above the upper surface of the north-dipping subduction zone. Sumbawa island is flanked to the north and south by two plates of oceanic crust. They are converging at a rate of 7.8 centimetres (3.1 in) per year. Strata deposition has drained a large magma chamber beneath the mountain. The Mojo islet was formed as part of the geological process in which Saleh Bay, collapsing into the caldera of the drained magma chamber, first appeared as a sea basin about 25,000 years ago.
According to a geological survey before the 1815 eruption, Tambora had the shape of a typical stratovolcano, with a symmetrical volcanic cone rising to 4,300 metres (14,100 ft) and having a single central vent. The diameter of the base was 60 kilometres (37 mi).
Ever since the 1815 eruption, the lowermost portion has contained deposits of interlayered sequences of lava and pyroclastic materials. The 1-4 metres (3 ft 3 in-13 ft 1 in) thick lava flows constitute about 40 percent of the layers' thickness. Thick scoria beds were produced by the fragmentation of lava flows. Within the upper section, the lava is interbedded with scoria, tuffs, and pyroclastic flows and falls. At least 20 subsidiary or parasitic cones are known. Some of them have names: Tahe, 844 metres (2,769 ft); Molo, 602 metres (1,975 ft); Kadiendinae; Kubah, 1,648 metres (5,407 ft); and Doro Api Toi. Most of these cones have produced basaltic lavas.
Eruptive history
Before 1815
Radiocarbon dating has established the dates of three of Mount Tambora's eruptions before the 1815 eruption, although their magnitudes are unknown. The estimated dates are between 4110 and 3700 BC, around 3050 BC, and sometime between 590 and 890 AD.
1815 and subsequent eruptions
In 1812, Mount Tambora became highly active, with its climactic eruption being the catastrophic and explosive event (VEI-7) of April 1815. This eruption ejected 160 cubic kilometres (38 cu mi) of tephra from the mountain's central vent. It also caused pyroclastic flows, collapsed the caldera, and caused tsunamis and extensive land and property damage. Although this activity ceased on 15 July 1815, it had a long-lasting effect on global climate. This was among the largest and most violent eruptions in the last 5000 years, along with the Hatepe eruption of Lake Taupo around 180 AD and the Tianchi eruption of Baekdu around 1000 AD.
Additional activity occurred in August 1819, consisting of a small eruption (VEI-2) with flames and rumbling aftershocks. It is considered part of the 1815 eruption sequence.
Mount Tambora has remained active since the end of the 1815 eruption sequence. Minor lava domes and flows were extruded on the caldera floor during the 19th and 20th centuries. Sometime between 1850 and 1910, Tambora erupted again but only inside the caldera. Small lava flows and lava dome extrusions were formed. This eruption (VEI-2) created the Doro Api Toi parasitic cone inside the caldera. A very small (VEI-0) and non-explosive eruption occurred in 1967; Another very small eruption was reported in 2011. In August 2011, the alert level for the volcano was raised from level I to level II after increasing activity was reported in the caldera, including earthquakes and smoke emissions.
Archaeological work
Archaeological evidence indicates that the 1815 eruption of Mount Tambora wiped out a culture on Sumbawa.
Ecosystem
A scientific team led by Swiss botanist Heinrich Zollinger arrived on Sumbawa in 1847 and ascended to the eastern rim of the caldera with the help of a native team. Zollinger's mission was to study the eruption scene and its effects on the local ecosystem. He was the first person to climb to the summit since the eruption. It was still covered by smoke. As Zollinger climbed, his feet broke through a thin surface crust into a warm layer of powder-like sulphur. Some vegetation had reestablished itself, and he saw a few trees on the lower slope and a Casuarina forest at 2,200-2,550 metres (7,220-8,370 ft). Several Imperata cylindrica grasslands also were found.
Resettlement of the mountain began in 1907. A coffee plantation was started in the 1930s on the north-western slope of the mountain in the village of Pekat. A dense rain forest, dominated by the pioneering tree Duabanga moluccana, had grown at an altitude of 1,000-2,800 metres (3,300-9,200 ft). It covers around 80,000 hectares (200,000 acres).
The rain forest and vegetation at higher altitudes were explored in 1933 by a Dutch team, led by Koster and de Voogd. From their accounts, they started their journey in a "fairly barren, dry and hot country" before entering "a mighty jungle" with "huge majestic forest giants". At 1,100 metres (3,600 ft), they entered a montane forest. Above 1,800 metres (5,900 ft), they found Dodonaea viscosa dominated by Casuarina trees. On the summit, they found sparse Anaphalis viscida and Wahlenbergia.
In 1896, 56 species of birds were found, including the crested white-eye. Twelve additional species were found in 1981. Subsequent zoological surveys found other bird species on the mountain. More than 90 bird species have been found on Mount Tambora. Local people hunt Yellow-crested cockatoos, Zoothera thrushes, hill mynas, green junglefowl, and rainbow lorikeets for the cagebird trade. Orange-footed scrubfowl are hunted for food. These exploitations have caused the bird population to decline. The yellow-crested cockatoo is nearing extirpation on Sumbawa island.
Since 1972, a commercial logging company has been operating in the area. The company holds a timber-cutting concession for approximately 25 percent of the area and covering 20,000 hectares (49,000 acres). Another part of the rain forest is used as a hunting ground. A wildlife reserve between the hunting ground and the logging area has deer, water buffalos, wild pigs, bats, flying foxes, and various species of reptiles and birds.
In 2015, the conservation area protecting the mountain's ecosystem was upgraded to a national park.
Caldera floor
The ecosystem that developed in the caldera after the 1815 eruption has been largely uninfluenced by human beings because of its isolation.
Monitoring Tambora
Indonesia's population has been increasing rapidly since the 1815 eruption, reaching 222 million in 2006, of which 130 million were living on Java. A new volcanic eruption as large as 1815 probably would cause catastrophic devastation with many more fatalities.
Seismic activity in Indonesia is monitored by the Directorate of Volcanology and Geological Hazard Mitigation, Indonesia. The monitoring post for Mount Tambora is located at Doro Peti village. They use a seismograph to measure seismic and tectonic activity. Since the 1880 eruption, no significant increase in seismic activity has occurred. Monitoring is performed continuously inside the caldera, especially around the Doro Api Toi parasitic cone.
The directorate has issued a hazard mitigation map for Mount Tambora. Two zones have been declared. The dangerous zone would be affected directly by pyroclastic flow, lava flow, and other pyroclastic falls. This area, including the caldera and its surroundings, covers up to 58.7 square kilometres (22.7 sq mi). Living in the dangerous zone is prohibited. The cautious zone includes areas that could be affected inditectly by lahar flows and other pumice stones. The size of this area is 185 square kilometres (71 sq mi) and includes the villages of Pasanggrahan, Doro Peti, Rao, Labuan Kenanga, Gubu Ponda, Kawindana To, and Hoddo. The river Guwu also is included in the cautious zone.
See also
- List of volcanic eruptions by death toll
- List of volcanoes in Indonesia
References
Further reading
- Anonymous (11 April 2015). "After Tambora". Briefing. Volcanoes and Climate. The Economist. 415 (8933): 17-20.
- C. R. Harrington, ed. (1992). The year without a summer? World climate in 1816. Ottawa: Canadian Museum of Nature.
- Henry and Elizabeth Stommel, Volcano Weather: The Story of 1816, the Year without a Summer, Newport, Rhode Island, 1983. ISBN 0-915160-71-4
- Gillen D'Arcy Wood, Tambora: The Eruption That Changed the World (Princeton, NJ: Princeton University Press, 2014). ISBN 978-0-691-15054-3
External links
- "Indonesia Volcanoes and Volcanics". Cascades Volcano Observatory. USGS. Retrieved 19 March 2006.
- "Tambora, Sumbawa, Indonesia". Volcano World. Department of Geosciences at Oregon State University.
- Tambora at Smithsonian Institution's Global Volcanism Program
Source of the article : Wikipedia
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