The eruption column lowered global temperatures, and this led to global cooling and worldwide harvest failures, sometimes known as the Year Without a Summer. The eruption resulted in a brief period of significant climate change that led to various cases of extreme weather. Several climate forcings coincided and interacted in a systematic manner that has not been observed since, despite other large eruptions that have occurred since the early Stone Age. Although the link between the post-eruption climate changes and the Tambora event has been established by various scientists, the understanding of the processes involved is incomplete.
False color image of Mount Tambora, taken from the Space Shuttle Endeavour on 13 May 1992 (for orientation, the top of the image is towards the East).
Mount Tambora experienced several centuries of dormancy before 1815, as the result of the gradual cooling of hydrous magma in a closed magma chamber. Inside the chamber at depths between 1.5 and 4.5 km (0.93 and 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 (400–500 MPa; 58,000–73,000 psi) was generated, and the temperature ranged from 700 to 850 °C (1,300–1,600 °F).[4] In 1812, the volcano began to rumble and generated a dark cloud.
On 5 April 1815, a huge 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 Molucca 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 sound of firing guns was heard on 10 April on Sumatra more than 2,600 km (1,600 mi) away.
At about 7 pm on 10 April, the eruptions intensified. Three columns of flame rose up and merged. The whole mountain was turned into a flowing mass of "liquid fire". Pumice stones of up to 20 cm (7.9 in) in diameter started to rain down around 8 pm, followed by ash at around 9–10 pm. 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.
The explosion is estimated to have been a VEI-7. An estimated 41 km3 (9.8 cu mi) of pyroclastic trachyandesite were ejected, weighing about 10000 million tonnes. 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. The density of fallen ash in Makassar was 636 kg/m³.[8] Before the explosion, Mount Tambora was about 4,300 m (14,100 ft) high, one of the tallest peaks in the Indonesian archipelago. After the explosion, it measured only 2,851 m (9,354 ft) (about two thirds of its previous height).
The 1815 Tambora eruption is the largest observed eruption in recorded history (see Table I, for comparison). The explosion was heard 2,600 km (1,600 mi) away, and ash fell at least 1,300 km (810 mi) away. Pitch darkness was observed as far away as 600 km (370 mi) from the mountain summit for up to two days. Pyroclastic flows spread at least 20 km (12 mi) from the summit. Due to the eruption, Indonesia's islands were struck by tsunami waves reaching heights up to 4 m (13 ft).
All vegetation on the island was destroyed. Uprooted trees, mixed with pumice ash, washed into the sea and formed rafts up to 5 km (3.1 mi) across.[5] One pumice raft was found in the Indian Ocean, near Calcutta on 1 and 3 October 1815.[10] 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 m (13 ft) in Sanggar around 10 pm. 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 to be around 4,600.
Current topography of Sumbawa
The eruption column reached the stratosphere, an altitude of more than 43 km (27 mi). The coarser ash particles fell one to two weeks after the eruptions, but the finer ash particles stayed in the atmosphere from a few months up to a few years at altitudes of 10–30 km (6.2–18.6 mi). Longitudinal winds spread these fine particles around the globe, creating optical phenomena. Prolonged and brilliantly coloured sunsets and twilights were frequently seen in London between 28 June and 2 July 1815 and 3 September and 7 October 1815. The glow of the twilight sky typically appeared orange or red near the horizon and purple or pink above.
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, 38,000 deaths were due to starvation, and another 10,000 deaths occurred due to disease and hunger on Lombok island. Petroeschevsky (1949) estimated about 48,000 and 44,000 people were killed on Sumbawa and Lombok, respectively. Several authors use Petroeschevsky's figures, such as Stothers (1984), who cites 88,000 deaths in total. However, Tanguy et al.. (1998) claimed Petroeschevsky's figures to be unfounded and based on untraceable references.
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. 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 posteruption famine and epidemic diseases. Oppenheimer (2003) stated a modified number of at least 71,000 deaths in total. Reid takes note of the total direct and indirect deaths caused beyond Sumbawa, in Bali and elsewhere, and suggests that a figure of perhaps 100,000 deaths is an appropriate estimate.
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. 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. 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.
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.
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.
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. 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), enough to cause significant agricultural problems around the globe. On 4 June 1816, frosts were reported in the upper elevations of New Hampshire, Maine, Vermont and northern New York. On 6 June 1816, snow fell in Albany, New York, and Dennysville, Maine. 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.
The second-coldest year in the Northern Hemisphere since c.1400 was 1816, and the 1810s are the coldest decade on record, a result of Tambora's 1815 eruption and another possible VEI 7 eruption that took place in late 1808 (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. As well as a cooler summer, parts of Europe experienced a stormier winter.
This climate anomaly has been blamed for the severity of typhus epidemics in southeast Europe and the eastern Mediterranean between 1816 and 1819. The climate changes disrupted the Indian monsoons, caused three failed harvests and famine contributing to the spread of a new strain of cholera originating in Bengal in 1816. Many livestock died in New England during the winter of 1816–1817. Cool temperatures and heavy rains resulted in failed harvests in 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 and 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.
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