Volcano of the Week!

09/12/2013-15/12/2013

This week’s ‘Volcano of the Week’ is;

Tambora

Location: Sumbawa, Lesser Sunda Islands, Indonesia

Type: Stratovolcano

Summit: 2850m

Elevation: 9348 ft

Last Eruption: 1967

Status: ACTIVE

Details:

According to radiocarbon dating Tambora’s first dated eruption was in 3910 BCE (± 200) years ago. Further eruptions took place in 350 BCE and 0740 (± 150 years). The intensity of these eruptions is unknown. The first observed and well documented eruption took place in 1815; the largest eruption for 10,000 years.

On 10^th April 1815 Tambora erupted. The eruption was a 7 on the Volcano Explosivity Index and released approximately 50 cubic km of magma and an ash plume over 40 km into the atmosphere during this Ultra-Plinian activity.

Devastation was caused by the eruption; pyroclastic flows travelled an estimated 20 km from the summit, ash fell around 1300 km from the volcano and even tsunamis were generated. Floating pumice travelled great distances from the volcano and there were reports of some found in Calcutta. The eruption was also heard 2600km away. Within 600 km of Tambora, darkness dominated for 3 days.

A 6km wide caldera was left behind by the eruption and changed the volcano’s elevation from 4300m to 2850m.

Tambora was responsible for the largest death toll ever caused by a volcano eruption. An estimated 11,000 people died directly from the impact of the eruption and an estimate total of 71,000 people died from both primary and secondary causes.

What made this eruption so devastating were the impacts felt globally.  The release of aerosols (including ash) into the atmosphere caused the sunlight to be blocked, therefore causing cooling in temperature. Temperatures fell 1 to 2.5 degree Celsius in New England and the British Isles and 0.4 to 0.7 degrees Celsius globally. This significant drop in temperature caused widespread famine and disease which claimed further lives. 1816 was known as ‘the year without summer’ due to the drop in temperature which caused crops to fail.

The figure below shows an isopach map of the extent and thickness of the ashfall from the eruption in 1815.

                  Source: (http://en.wikipedia.org/wiki/File:1815_tambora_explosion.png)

In April 2011, increased seismic activity was recorded on the volcano and continued well into September 2011. Based on this activity along with an observation of white plumes being emitted, scientists raised the alert level from 2 to 3 on a scale of 1-4. In October, decrease in activity led to the alert level being changed from 3 to 2 and from 2 to 1 in April 2012. The alert level was once again increased to 2 in April 2013 due to seismic activity and observations.