Mount Tambora

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Mount Tambora
Caldera Mt Tambora Sumbawa Indonesia.jpg
Aerial view of the caldera of Mount Tambora, formed during the colossal 1815 eruption.
Elevation 2,850 m (9,350 ft)[1][2]
Prominence 2,850 m (9,350 ft)[1][3]
Listing Ultra
Ribu
Location
Mount Tambora is located in Indonesia
Mount Tambora
Mount Tambora
Location in Indonesia
Location Sumbawa, Lesser Sunda Islands, Indonesia
Coordinates 8°14′48″S 117°57′30″E / 8.24667°S 117.95833°E / -8.24667; 117.95833Coordinates: 8°14′48″S 117°57′30″E / 8.24667°S 117.95833°E / -8.24667; 117.95833[2]
Geology
Type Stratovolcano/Caldera
Age of rock 57,000 years
Last eruption 1967 ± 20 years[1]

Mount Tambora (or Tamboro) is an active stratovolcano on the island of Sumbawa, Indonesia. Sumbawa is flanked both to the north and south by oceanic crust, and Tambora was formed by the active subduction zone beneath it. This raised Mount Tambora as high as 4,300 m (14,100 ft),[4] making it, in the 18th century, one of the tallest peaks in the Indonesian archipelago. After a large magma chamber inside the mountain filled over the course of several decades, volcanic activity reached a historic climax in the eruption of 10 April 1815.[5] This eruption was approximately VEI-7, the only eruption unambiguously confirmed of that size since the Lake Taupo eruption in about AD 180.[6]

With an estimated ejecta volume of 160 km3 (38 cu mi), Tambora's 1815 outburst was the largest volcanic eruption in recorded history. The explosion was heard on Sumatra island more than 2,000 km (1,200 mi) away. Heavy volcanic ash falls were observed as far away as Borneo, Sulawesi, Java and Maluku islands. Most deaths from the eruption were from starvation and disease, as the eruptive fallout ruined agricultural productivity in the local region. The death toll was at least 71,000 people, of whom 11,000–12,000 were killed directly by the eruption;[6] the often-cited figure of 92,000 people killed is believed to be overestimated.[7]

The eruption caused global climate anomalies that included the phenomenon known as "volcanic winter": 1816 became known as the "Year Without a Summer" because of the effect on North American and European weather. Crops failed and livestock died in much of the Northern Hemisphere, resulting in the worst famine of the 19th century.[6]

During an excavation in 2004, a team of archaeologists discovered cultural remains buried by the 1815 eruption.[8] They were kept intact beneath the 3 m (9.8 ft) deep pyroclastic deposits. At the site, dubbed the Pompeii of the East, the artifacts were preserved in the positions they had occupied in 1815.

Geographical setting[edit]

Topographic map of Tambora and Sumbawa
Mt. Tambora and its surroundings as seen from space

Mount Tambora is on Sumbawa Island, part of the Lesser Sunda Islands. It is a segment of the Sunda Arc, a string of volcanic islands that forms the southern chain of the Indonesian archipelago.[9] Tambora forms its own peninsula on Sumbawa, known as the Sanggar peninsula. At the north of the peninsula is the Flores Sea, and at the south is Saleh Bay, 86 km (53 mi) long and 36 km (22 mi) wide. At the mouth of Saleh Bay there is a 30,000 hectares (74,000 acres) islet called Moyo (Indonesian: Pulau Moyo) which has a resort where Princess Diana once stayed.[10]

Besides its interest for seismologists and volcanologists, who monitor the mountain's activity, Mount Tambora is an area of scientific studies for archaeologists and biologists. The mountain also attracts tourists for hiking and wildlife activities.[11][12] The two nearest cities are Dompu and Bima. There are three concentrations of villages around the mountain slope. At the east is Sanggar village, to the northwest are Doro Peti and Pesanggrahan villages, and to the west is Calabai village.

There are three ascent routes to reach the caldera.

  • The first route starts from Doro Mboha village south of the mountain. This route follows a paved road through a cashew plantation until it reaches 1,150 m (3,770 ft) above sea level. The end of this route is the southern part of the caldera at 1,950 m (6,400 ft), reachable by a hiking track.[13] This place is usually used as a base camp to monitor the volcanic activity, because it only takes one hour to reach the caldera.
  • The second route is southwest of the mountain, starting from Doro Peti village. The Tambora volcanic monitoring station is in this village.
  • The third route starts from Pancasila village northwest of the mountain. This route passes through a coffee plantation. Using the third route, the caldera is accessible only by foot.[13] The highest point of Tambora is located on a hill near the westen rim of the caldera.

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.[14] In September 2011 the alert level was raised to Level III after further increases in activity.[15]

Geological history[edit]

Formation[edit]

Tambora is 340 km (210 mi) north of the Java Trench system and 180–190 km (110–120 mi) above the upper surface of the active north-dipping subduction zone. Sumbawa island is flanked to both the north and south by the oceanic crust.[16] The convergence rate is 7.8 cm (3.1 in) per year.[17] Tambora is estimated to have started forming around 57,000 years ago.[5] Depositing its strata has drained off a large magma chamber inside the mountain. The Mojo islet was formed as part of this 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.[5]

According to a geological survey, before the 1815 eruption Tambora had the shape of a typical stratovolcano, with a high symmetrical volcanic cone and a single central vent.[18] The diameter at the base is 60 km (37 mi).[9] The central vent frequently emitted lava, which cascaded down a steep slope.

Since the 1815 eruption, the lowermost portion contains deposits of interlayered sequences of lava and pyroclastic materials. The 1–4 m (3.3–13.1 ft) thick lava flows constitute approximately 40% of the layers' thickness.[18] Thick scoria beds were produced by fragmentation of lava flows. In the upper section, the lava is interbedded with scoria, tuffs and pyroclastic flows and falls.[18] There are at least twenty subsidiary or parasitic cones.[17] Some of them have names: Tahe, 844 m (2,769 ft); Molo, 602 m (1,975 ft); Kadiendinae; Kubah, 1,648 m (5,407 ft); and Doro Api Toi. Most of these parasitic cones have produced basaltic lavas.

Eruptive history[edit]

The summit caldera of the volcano

Use of the radiocarbon dating technique has established the dates of three of Mount Tambora's eruptions prior to the 1815 eruption. The magnitudes of these eruptions are unknown.[19] The estimated dates are 3910 BC ± 200 years, 3050 BC and 740 AD ± 150 years. They were all explosive central vent eruptions with similar characteristics, except that the 740 AD eruption had no pyroclastic flows.

In 1812, Mount Tambora entered a period of high activity, with its climactic eruption being the catastrophic explosive event of April 1815.[19] The VEI 7 eruption had a total tephra ejecta volume of 160 km3 (38 cu mi).[19] It was an explosive central vent eruption with pyroclastic flows and a caldera collapse, causing tsunamis and extensive land and property damage. It had a long-term effect on global climate. This activity ceased on 15 July 1815.[19] Follow-up activity was recorded in August 1819 consisting of a small eruption (VEI = 2) with flames and rumbling aftershocks, and was considered to be part of the 1815 eruption sequence.[6] Around 1880 ± 30 years, Tambora went into eruption again, but only inside the caldera.[19] Small lava flows and lava dome extrusions were formed. This eruption (VEI = 2) created the Doro Api Toi parasitic cone inside the caldera.[20]

Mount Tambora is still active. Minor lava domes and flows have been extruded on the caldera floor during the 19th and 20th centuries.[1] The last eruption was recorded in 1967.[19] However, it was a very small, non-explosive eruption (VEI = 0).

1815 eruption[edit]

1815 eruption of Mount Tambora
1815 tambora explosion.png
The estimated volcanic ashfall regions during the 1815 eruption. The red areas show thickness of volcanic ashfall. The outermost region (1 cm thickness) reached Borneo and Sulawesi.
Volcano Mount Tambora
Date 1815
Type Ultra Plinian
Location Sumbawa, Lesser Sunda Islands, Dutch East Indies
VEI 7
Impact Reduced global temperatures, leading the following year, 1816, to be called the Year Without a Summer.

The 1815 eruption of Mount Tambora was one of the most powerful in recorded history and classified as a VEI-7 event. Mount Tambora is on the island of Sumbawa in Indonesia. The eruption that began on 10 April 1815[21] was preceded by between six months and three years of increased steaming and small phreatic eruptions. The eruption column lowered global temperatures, and some experts believe this led to global cooling and worldwide harvest failures, sometimes known as the Year Without a Summer.[22]

Chronology of the eruption[edit]

Mount Tambora experienced several centuries of dormancy before 1815 as the result of the gradual cooling of hydrous magma in a closed magma chamber.[9] Inside the chamber at depths between 1.5–4.5 km (0.93–2.80 mi), the exsolution of a high-pressure fluid magma formed during cooling and crystallisation of the magma. Overpressure of the chamber of about 4,000–5,000 bar (58,000–73,000 psi) was generated, and the temperature ranged from 700–850 °C (1,292–1,562 °F).[9] In 1812, the caldera began to rumble and generated a dark cloud.[4]

On 5 April 1815, a moderate-sized eruption occurred, followed by thunderous detonation sounds, heard in Makassar on Sulawesi 380 km (240 mi) away, Batavia (now Jakarta) on Java 1,260 km (780 mi) away, and Ternate on the Maluku Islands 1,400 km (870 mi) away. On the morning of 6 April, volcanic ash began to fall in East Java with faint detonation sounds lasting until 10 April. What was first thought to be the sound of firing guns was heard on 10 April on Sumatra island more than 2,600 km (1,600 mi) away.[23]

At about 7 p.m. on 10 April, the eruptions intensified.[4] Three columns of flame rose and merged.[23] The whole mountain was turned into a flowing mass of "liquid fire".[23] Pumice stones of up to 20 cm (7.9 in) in diameter started to rain down at approximately 8 p.m., followed by ash at around 9–10 p.m. Pyroclastic flows cascaded down the mountain to the sea on all sides of the peninsula, wiping out the village of Tambora. Loud explosions were heard until the next evening, 11 April. The ash veil had spread as far as West Java and South Sulawesi. A "nitrous" odour was noticeable in Batavia and heavy tephra-tinged rain fell, finally receding between 11 and 17 April.[4]

The first explosions were heard on this Island in the evening of 5 April, they were noticed in every quarter, and continued at intervals until the following day. The noise was, in the first instance, almost universally attributed to distant cannon; so much so, that a detachment of troops were marched from Djocjocarta, in the expectation that a neighbouring post was attacked, and along the coast boats were in two instances dispatched in quest of a supposed ship in distress.

Sir Stamford Raffles' memoir.[23]

The explosion is estimated to have been VEI 7.[24] It had roughly four times the energy of the 1883 Krakatoa eruption, meaning that it was equivalent to an 800 Mt (3.3×1012 MJ) explosion. An estimated 160 km3 (38 cu mi) of pyroclastic trachyandesite was ejected, weighing approximately 140×10^12 kg (310×10^12 lb) (see above). This has left a caldera measuring 6–7 km (3.7–4.3 mi) across and 600–700 m (2,000–2,300 ft) deep.[4] The density of fallen ash in Makassar was 636 kg/m² (130.3 lb/sq ft).[25] Before the explosion, Mount Tambora was approximately 4,300 m (14,100 ft) high,[4] one of the tallest peaks in the Indonesian archipelago. After the explosion, it now measures only 2,851 m (9,354 ft).[26]

Impact of the eruption[edit]

By most calculations, the eruption of Tambora was at least a full order of magnitude larger than that of Mount Pinatubo in 1991 (Graft et al. 1993). It is estimated that the top 1,220 metres (4,000 ft) of the mountain was reduced to rubble and ash as a result of the eruption, and was subsequently ejected from the mountain or fell into the new caldera, reducing Tambora's height by a third.[27] Around 100 cubic kilometers of rock was blasted into the air, eclipsing the estimated 10 cubic kilometers by its counterpart in Italy, Vesuvius (Williams 2012). Not only were rocks and ash expelled into the atmosphere, but toxic gases were pumped into the atmosphere as well. Many of the residents who survived the resulting tsunami, eruption, or ash cloud became sick due to all of the sulfur, which caused lung infections (Cole-Dai et al. 2009). Volcanic ash was documented to be over 1 m deep in areas within 75 km of the eruption, and ash could be found as far away as 1300 km.[6] With this much volcanic ash on the ground, any crops or viable vegetation sources were smothered at a minimum and burned if they were close to the volcano itself. This created an immediate shortage of food in Indonesia, one that only compounded the regular shortage during the winter season (Cole-Dai et al. 2009). The ejection of these gasses, especially HCl, caused the precipitation that followed in the region to be extremely acidic, killing much of the crops that either survived or were rebudding during the spring. The food shortage was compounded by the Napoleonic wars, floods, and cholera.[6]

The presence of ash in the atmosphere for several months after the eruption reflected significant amounts of solar radiation, causing unseasonably cool summers which further drove populations to a food shortage.[6] China, Europe, and North America all had well-documented cases of abnormal temperatures, decimating their harvests. These climatic shifts also altered the monsoon season in China and India, forcing thousands of Chinese to flee coastal areas due to regional flooding of the Yangtze Valley (Granados et al. 2012). The gases also reflected some of the already decreased incoming solar radiation, causing a notable decrease in global temperatures throughout the decade, between 0.4-0.7 °C globally. It was so dramatic that that an ice dam was formed in Switzerland during the summer of 1816 and 1817, earning 1816 the title "Year without a summer" or YWAS.[28] The winter months of 1816 were not very different from years previous, but the spring and summer maintained the cool to freezing temperatures. However, the winter of 1817 radically differed, reaching temperatures below -30 °F in New York, which were cold enough to freeze lakes and rivers used for transporting supplies. Both Europe and North America suffered late freezes that lasted well into June with snow accumulating up to 32 cm in August, which killed recently planted crops, crippling the food industry. Unseasonably cool temperatures reduced the output of crops worldwide: the growing seasons in Massachusetts and New Hampshire were less than 80 days in 1816, citing freezing temperatures as the reason for harvest failure (Oppenheimer 2003). These were visually connected to unique sunsets observed in western Europe and red fog found on the Eastern Seaboard of the US. These unique atmospheric conditions persisted for the better part of 2.5 years (Robock 2000).

Ice cores have been used to monitor atmospheric gases during the cold decade (1810-1819). The SO4 concentration found in both Central Greenland and Siple Station, Antarctica, spiked in January 1816 but had fallen back by August 1818.[29] This means that 25-30 Tg of sulfur was ejected into the atmosphere, most of which would come from Tambora, and was equalized back by natural processes on Earth rather quickly. Another unique factor is that Tambora represents the largest shift in sulfur concentration in the ice cores for the past 5000 years, potentially becoming the single most disruptive event in recorded history. Estimates of the sulfur yield vary from 10 Tg (Black et al. 2012) to 120 Tg (Stothers 2000). The difference between the models are drastic, but many estimates will either average in or agree on a number between 25-30 Tg. The high concentration might explain the stratospheric warming of ~15 °C, resulting in surface cooling that would be a delayed reaction lasting for the next nine years. It is estimated that the stratospheric warming event only lasted four years, but cooler temperatures were documented until 1825 (Cole-Dai et al. 2009). The data presented did not state whether it was a statistically significant difference or just temperatures cooler than "normal". This has been dubbed a "volcanic winter", similar to a nuclear winter, due to the overall decrease and abysmal farming conditions.[6]

Climate data have shown that the variance between daily lows and highs may have played a role in the lower average temperature because the fluctuations were much more subdued. Generally, the mornings were warmer due to nightly cloud cover and the evenings were cooler because the clouds had dissipated. There were documented fluctuations of cloud cover for various locations that suggested it was a nightly occurrence and the sun killed them off, much like a fog (Oppenheimer 2003). The class boundaries between 1810-1830 without volcanically perturbed years was ~7.9 °C. This is contrasted by the volcanically perturbed years (1815-1817) where the delta was only ~2.3 °C. This meant that the mean annual cycle in 1816 was more linear than bell shaped and 1817 endured cooling across the board. Southeastern England, northern France, and the Netherlands experienced the greatest amount of cooling in Europe; complemented by New York, New Hampshire, Delaware, and Rhode Island in North America.[28]

The documented rainfall was as much as 80% more than the calculated normal with regards to 1816, unusually high amounts of snow were found in Switzerland, France, Germany, and Poland. This is again contrasted by the unusually low precipitations in 1818 which caused droughts throughout most of Europe and Asia (Auchmann et al. 2012). Russia had already experienced unseasonably warm and dry summers since 1815 and this continued for the next three years. There are also documented reductions in ocean temperature near the Baltic Sea, North Sea, and Mediterranean. This seems to have been an indicator of shifted oceanic circulation patterns and possibly changed wind direction and speed (Meronen et al. 2012). This is further supported by the recorded observations of a British fleet sent to explore the Arctic Circle; they found large ice sheets that were miles off the coast of Greenland, where two years prior they had been shoved along the eastern border of the island. Contemporary scientists attributed the Year Without a Summer to the drifting polar ice sheets rather than the eruption of Tambora because of its proximity to England.[6]

Taking into account the Dalton Minimum, and the presence of famine and droughts predating the eruption, the Tambora volcanic event accelerated or exacerbated the extreme climate conditions of 1815. While other eruptions and other climatological events would have led to a global cooling of about 0.2 °C, Tambora increased that number substantially.[29] This is a case of extreme climate, not extreme weather. Several climate forcings coincided and interacted in a way not experienced since, even with large eruptions since early 20th century. Our current understanding of these events and their link to the Tambora event is well-defined; yet there are many concerns that our understanding of such an event is limited and would not prove substantial if a subsequent eruption of the same magnitude were to occur.

Aftermath[edit]

On my trip towards the western part of the island, I passed through nearly the whole of Dompo and a considerable part of Bima. The extreme misery to which the inhabitants have been reduced is shocking to behold. There were still on the road side the remains of several corpses, and the marks of where many others had been interred: the villages almost entirely deserted and the houses fallen down, the surviving inhabitants having dispersed in search of food.
...
Since the eruption, a violent diarrhoea has prevailed in Bima, Dompo, and Sang'ir, which has carried off a great number of people. It is supposed by the natives to have been caused by drinking water which has been impregnated with ashes; and horses have also died, in great numbers, from a similar complaint.

—Lt. Philips, ordered by Sir Stamford Raffles to go to Sumbawa.[23]

All vegetation on the island was destroyed. Uprooted trees, mixed with pumice ash, washed into the sea and formed rafts of up to 5 km (3.1 mi) across.[4] One pumice raft was found in the Indian Ocean, near Calcutta on 1 and 3 October 1815.[6] Clouds of thick ash still covered the summit on 23 April. Explosions ceased on 15 July, although smoke emissions were still observed as late as 23 August. Flames and rumbling aftershocks were reported in August 1819, four years after the event.

A moderate-sized tsunami struck the shores of various islands in the Indonesian archipelago on 10 April, with a height of up to 4 metres (13 ft) in Sanggar at around 10 p.m.[4] A tsunami of 1–2 m (3.3–6.6 ft) in height was reported in Besuki, East Java, before midnight, and one of 2 metres (6.6 ft) in height in the Molucca Islands. The total death-toll has been estimated at around 4,600.[30]

The eruption column reached the stratosphere, an altitude of more than 43 km (27 mi).[6] The coarser ash particles fell 1 to 2 weeks after the eruptions, but the finer ash particles stayed in the atmosphere from a few months up to a few years at an altitude of 10–30 km (6.2–18.6 mi).[4] Longitudinal winds spread these fine particles around the globe, creating optical phenomena. Prolonged and brilliantly coloured sunsets and twilights were frequently seen in London, England between 28 June and 2 July 1815 and 3 September and 7 October 1815.[4] The glow of the twilight sky typically appeared orange or red near the horizon and purple or pink above, influencing J. M. W. Turner's paintings.

The estimated number of deaths varies depending on the source. Zollinger (1855) puts the number of direct deaths at 10,000, probably caused by pyroclastic flows. On Sumbawa island, there were 38,000 deaths due to starvation, and another 10,000 deaths occurred due to disease and hunger on Lombok island.[31] Petroeschevsky (1949) estimated about 48,000 and 44,000 people were killed on Sumbawa and Lombok, respectively.[32] Several authors use Petroeschevsky's figures, such as Stothers (1984), who cites 88,000 deaths in total.[4] However, Tanguy et al.. (1998) claimed Petroeschevsky's figures to be unfounded and based on untraceable references.[7] Tanguy revised the number solely based on two credible sources, q.e., Zollinger, who himself spent several months on Sumbawa after the eruption, and Raffles's notes.[23] Tanguy pointed out that there may have been additional victims on Bali and East Java because of famine and disease. Their estimate was 11,000 deaths from direct volcanic effects and 49,000 by post-eruption famine and epidemic diseases.[7] Oppenheimer (2003) stated a modified number of at least 71,000 deaths in total, as seen in Table I below.[6]

Global effects[edit]

Sulfate concentration in ice core from Central Greenland, dated by counting oxygen isotope seasonal variations. There is an unknown eruption around the 1810s. Source: Dai (1991).[29]

The 1815 eruption released sulfur dioxide (SO2) into the stratosphere, causing a global climate anomaly. Different methods have estimated the ejected sulphur mass during the eruption: the petrological method; an optical depth measurement based on anatomical observations; and the polar ice core sulfate concentration method, using cores from Greenland and Antarctica. The figures vary depending on the method, ranging from 10 to 120 million tonnes.[6]

In the spring and summer of 1815, a persistent dry fog was observed in the northeastern United States. The fog reddened and dimmed the sunlight, such that sunspots were visible to the naked eye. Neither wind nor rainfall dispersed the "fog". It was identified as a stratospheric sulfate aerosol veil.[6] In summer 1816, countries in the Northern Hemisphere suffered extreme weather conditions, dubbed the Year Without a Summer. Average global temperatures decreased about 0.4–0.7 °C (0.7–1.3 °F),[4] enough to cause significant agricultural problems around the globe. On 4 June 1816, frosts were reported in Connecticut, and by the following day, most of New England was gripped by the cold front. On 6 June 1816, snow fell in Albany, New York, and Dennysville, Maine.[6] Such conditions occurred for at least three months and ruined most agricultural crops in North America. Canada experienced extreme cold during that summer. Snow 30 cm (12 in) deep accumulated near Quebec City from 6 to 10 June 1816.

1816 was the second coldest year in the northern hemisphere since AD 1400, after 1601 following the 1600 Huaynaputina eruption in Peru.[24] The 1810s are the coldest decade on record, a result of Tambora's 1815 eruption and other suspected eruptions somewhere between 1809 and 1810 (see sulfate concentration figure from ice core data). The surface temperature anomalies during the summer of 1816, 1817 and 1818 were −0.51 °C (−0.92 °F), −0.44 °C (−0.79 °F) and −0.29 °C (−0.52 °F), respectively.[24] As well as a cooler summer, parts of Europe experienced a stormier winter.

This pattern of climate anomaly has been blamed for the severity of typhus epidemic in southeast Europe and the eastern Mediterranean between 1816 and 1819.[6] The climate changes disrupted Indian monsoons causing three failed harvests and famine contributing to worldwide spread of a new strain of cholera originating in Bengal in 1816.[33] Much livestock died in New England during the winter of 1816–1817. Cool temperatures and heavy rains resulted in failed harvests in the United Kingdom of Great Britain and Ireland. Families in Wales travelled long distances as refugees, begging for food. Famine was prevalent in north and southwest Ireland, following the failure of wheat, oat and potato harvests. The crisis was severe in Germany, where food prices rose sharply. Due to the unknown cause of the problems, demonstrations in front of grain markets and bakeries, followed by riots, arson and looting, took place in many European cities. It was the worst famine of the 19th century.[6]

Disruption of global temperatures[edit]

The conditions during the northern hemisphere summer of 1816 were the result of the largest observed eruption in recorded human history, one during which global temperatures decreased by an average of 0.53 °C, and related human deaths were reported to be about 90,000. The importance of volcanic eruptions during this anomaly, specifically the eruption of Mount Tambora, cannot be overlooked. It is the most significant factor in this important climate anomaly across the globe (Robock 2000). While there were other eruptions during the year of 1815, Tambora is classified as a VEI-7 and an eruption column 45 km tall, eclipsing all others by at least one order of magnitude.

The Volcanic Explosivity Index (VEI) is used to quantify the amount of ejected material with a VEI-7 coming in at 100 km3. Every index value below that is one order of magnitude less. Furthermore, the 1815 eruption occurred during a Dalton Minimum, a period of unusually low solar radiation (Auchmann et al. 2012). Volcanism plays a large role in climate shifts, both locally and globally. This was not always understood and did not enter scientific circles as fact until Krakatau erupted in 1883 and tinted the skies orange (Robock 2000).

The scale of the volcanic eruption will determine the significance of the impact on climate and other chemical processes, but a change will be measured even in the most local of environments. When volcanoes erupt they eject CO2, H2O, H2, SO2, HCl, HF, and many other gases (Meronen et al. 2012). CO2 and H2O are greenhouse gases, responsible for 0.0394% and 0.4% of the atmosphere respectively. Their small ratio disguises their significant role in trapping solar insolation and reradiating it back to Earth.

Comparison of selected volcanic eruptions[edit]

Eruptions Country Location Year Column
height (km)
 Volcanic
Explosivity Index 
N. hemisphere
summer anomaly (°C)
Fatalities
Mount Vesuvius Italy Mediterranean 79 30 5  ? 02001>2,000
Hatepe (Taupo) New Zealand Pacific Ring of Fire 186 51 7  ? 00000?
Baekdu China / North Korea Pacific Ring of Fire 969 25 6–7  ? 00000?
Kuwae Vanuatu Pacific Ring of Fire 1452  ? 6 −0.5 00000?
Huaynaputina Peru Pacific Ring of Fire 1600 46 6 −0.8 01400≈1,400
Tambora Indonesia Pacific Ring of Fire 1815 43 7 −0.5 71001>71,000
Krakatoa Indonesia Pacific Ring of Fire 1883 36 6 −0.3 3600036,600
Santa María Guatemala Pacific Ring of Fire 1902 34 6 no anomaly 070017,000–13,000
Novarupta USA, Alaska Pacific Ring of Fire 1912 32 6 −0.4 000022
Mt. St. Helens USA, Washington Pacific Ring of Fire 1980 19 5 no anomaly 0005757
El Chichón Mexico Pacific Ring of Fire 1982 32 4–5 YES 02001>2,000
Nevado del Ruiz Colombia Pacific Ring of Fire 1985 27 3 no anomaly 2300023,000
Pinatubo Philippines Pacific Ring of Fire 1991 34 6 −0.5 012021,202

Source: Oppenheimer (2003),[6] and Smithsonian Global Volcanism Program for VEI.[34]

Effects of volcanism[edit]

Volcanism affects the atmosphere in two distinct ways: short-term cooling due to reflected insolation, and long-term warming due to increased CO2 levels. Most of the water vapor and CO2 is collected in clouds within a few weeks to months because both are already present in large quantities, so the effects are limited (Bodenmann et al. 2011). SO2, along with other aerosols and particulates, is responsible for global cooling, nullifying the effects of the greenhouse gas emissions due to its ability to be found higher in the atmosphere and its efficiency at bonding with any water vapor found in the upper "dry" atmosphere. Sulfuric acid is exceptional at blocking solar radiation and it usually takes months to years for it to acquire enough water vapor to fall back to Earth. This means that an already smaller amount of insolation could have reflected at higher rates for up to 3 years (Granados et al. 2012) This is reflected by ice core data and averaged thermometer readings throughout the world. Places in central Canada and Russia experienced warming events of ~0.1 °C which are credited to the chain of eruptions from 1810–1815.[29]

Archaeological work[edit]

See Tambora culture for details about 2004 work on exploring for villages and people lost at the time of the major eruption.

Ecosystem[edit]

A scientific team led by a Swiss botanist, Heinrich Zollinger, arrived on Sumbawa in 1847.[35] 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 after the eruption. It was still covered by smoke. As Zollinger climbed up, his feet sank several times through a thin surface crust into a warm layer of powder-like sulphur. Some vegetation had re-established itself and a few trees were observed on the lower slope. A Casuarina forest was noted at 2,200–2,550 m (7,220–8,370 ft).[36] Several Imperata cylindrica grasslands were also found.

Rehabitation of the mountain began in 1907. A coffee plantation was started in the 1930s on the northwestern slope of the mountain, in the village of Pekat.[37] A dense rain forest, dominated by the pioneering tree, Duabanga moluccana, had grown at an altitude of 1,000–2,800 m (3,300–9,200 ft).[37] It covers an area up to 80,000 ha (200,000 acres). The rain forest was explored by a Dutch team, led by Koster and de Voogd in 1933.[37] From their accounts, they started their journey in a "fairly barren, dry and hot country", and then they entered "a mighty jungle" with "huge, majestic forest giants". At 1,100 m (3,600 ft), they entered a montane forest. Above 1,800 m (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.[38] Twelve further species were found in 1981. Several other zoological surveys followed, and found other bird species on the mountain, resulting in over 90 bird species discovered on Mount Tambora. Yellow-crested Cockatoos, Zoothera thrushes, Hill Mynas, Green Junglefowl and Rainbow Lorikeets are hunted for the cagebird trade by the local people. Orange-footed Scrubfowl are hunted for food. This bird exploitation has resulted in a decline in the bird population. The Yellow-crested Cockatoo is nearing extinction on Sumbawa island.[38]

Since 1972, a commercial logging company has been operating in the area, which poses a large threat to the rain forest. The logging company holds a timber-cutting concession for an area of 20,000 ha (49,000 acres), or 25% of the total area.[37] Another part of the rain forest is used as a hunting ground. In between the hunting ground and the logging area, there is a designated wildlife reserve where deer, water buffalos, wild pigs, bats, flying foxes, and various species of reptiles and birds can be found.[37]

Monitoring[edit]

Infrared image of Mount Tambora

Indonesia's population has been increasing rapidly since the 1815 eruption. As of 2006, the population of Indonesia has reached 222 million people,[39] of which 130 million are concentrated on Java.[40] A contemporary volcanic eruption as large as Tambora's 1815 eruption would cause catastrophic devastation with likely many more fatalities. Therefore, volcanic activity in Indonesia is continuously monitored, including that of Mount Tambora. Seismic activity in Indonesia is monitored by the Directorate of Vulcanology and Geological Hazard Mitigation, Indonesia. The monitoring post for Mount Tambora is located at Doro Peti village.[41] They focus on seismic and tectonic activities by using a seismograph. Since the 1880 eruption, there has been no significant increase in seismic activity.[42] However, monitoring is continuously performed inside the caldera, especially around the parasitic cone Doro Api Toi.

The directorate has defined a hazard mitigation map for Mount Tambora. Two zones are declared: the dangerous zone and the cautious zone.[41] The dangerous zone is an area that will be directly affected by an eruption: pyroclastic flow, lava flow and other pyroclastic falls. This area, including the caldera and its surroundings, covers up to 58.7 km2 (22.7 sq mi). Habitation of the dangerous zone is prohibited. The cautious zone includes areas that might be indirectly affected by an eruption: lahar flows and other pumice stones. The size of the cautious area is 185 km2 (71 sq mi), and includes Pasanggrahan, Doro Peti, Rao, Labuan Kenanga, Gubu Ponda, Kawindana Toi and Hoddo villages. The river Guwu at the southern and northwest part of the mountain is also included in the cautious zone.[41]

See also[edit]

References[edit]

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Further reading[edit]

External links[edit]