Category Archives: Sumatra

Sinabung Claims More Lives

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Sadly I awoke this morning to the news Mount Sinabung in Northern Sumatra, Indonesia had claimed the lives of three farmers working in the fields by the Gembar Village. This figure has since risen to 7 and is feared to continue to rise with several more critically injured and the Red Cross and army looking for further victims.

Mount Sinabung has been in a near constant state of eruption since late 2013. Pyroclastic flows sweep down its flanks on a regular basis which has lead to 4 km exclusion zone being enforced around the summit.  On February 1st 2014 people were killed by one such pyroclastic flows.

About 10,000 people have been displaced by activity at the volcano which has been on the highest state of alert for well over a year. Sadly the volcano is positioned in a relatively poor and over populated area of the world, many people have little choice but to continue to farm on the volcanoes fertile flanks. Officials have struggled to keep the people to stick the ‘red’ exclusion zones and it is unclear how many people were on the mountain at the time of the recent activity.

Head of the National Disaster Mitigation Agency (BNPB) Willem Rampangilei has instructed Karo Regent to take quick measures to vacate the red zones (Gamber village, Simpang Empat district and Karo Regency) but they know that this is easier said then done. The pyroclastic flows caused by partial collapses of the growing lava dome occurred in a series at 14:28, 15:08 and 16:39 local time on Saturday. Rescue attempts went through the night and in to Sunday morning. An ash column remained for hours, towering over the area darkening the skys and hampering the search operation.

The pyroclastic flow captured here to the left happened only a week ago on May 16th showing the power and regularity of such activity. On May 9th a lahar swept through  Kutambaru near the Lau Barus River killing 1 and leaving one person still missing now also presumed dead.

Sinabung lay silently for nearly 400 year until springing back to life back in 2010. It has now killed at least 25 people since its rousing. Volcanism on the island of Sumatra is caused by the subduction of the Indo-Australian plate beneath the Eurasian plate along the Sunda Arc which creates the andesitic-dacitic composition magmas which are prone to such explosive activity. Sinabung sits just 25 miles north-east of the Toba Super Volcano caused by the same tectonic motion.

 

Figures 1 and 2; posted to Facebook by SkyAlert.

Figure 3; http://www.volcanodiscovery.com/sinabung/news.html

 

Eruption Update

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I may have bee quiet on eruption updates lately but that is far from meaning our restless Earth has been quiet. Here is some of the recent updates.

Kilauea 

As Kilauea has been in a constant state of eruption since 1983, some don’t consider changes in activity as news. However as the June 27th lava showed us this relatively calm giant still poses a threat to people.

USGS reports suggest that the summit is still inflating; 7.5 microradians were recorded in the past week alone. Over the weekend we saw rapid filling of the Halema’uma’u crater from a depth of 90 ft from the crater rim to within 10 ft by Sunday lunch time. Yesterday (April 29th) the webcam observed small explosions and spattering with rock falls as the crater began to overflow.

Seismicity remains at an increased level towards the summit and East rift zone where wide spread breakouts from the eruption site are active as close as 8 km of Pu’u ‘O’o. There has be net inflation of Pu’u ‘O’o over the past week but not as significant as at the summit. As the June 27th Lava flows nears its 1 year anniversary incandesance indicates that surface flows remain active northeast of Pu’u ‘O’o.

Calbuco

Although the more explosive phase of the eruption seems to have died down, there are still high ash emissions and flight disruption is still an issue across both Chile and Argintina with ash plumes trailing to the north and south east at just over 1.5 km high. The 20 km exclusion zone is still inplace however it is belived that some people have returned to their homes within the area with maximum displaced 6,514 at the begining of this week. Seismicity has since declinded but it is still under observation.

Sinabung

Collapse of the lava dome on April 28th caused a pyroclastic flow to surge down the flanks. Luckily exclusion zones are still in place from activity over the past few months. The Darwin VAAC  said an ash columb exceeds 14,000 ft although satalitte confirmation has not been possible due to cloud coverage.

Aira

JMA reported that 29 explosions from Showa Crater at Aira Caldera’s Sakurajima volcano ejected tephra as far as 1,300 m during 20-24 April. Nine of the explosions generated ash plumes that rose 3 km above the crater rim; one explosion, on 24 April, produced an ash plume that rose 4 km. Incandescence from the crater was visible on one night. The Alert Level remained at 3 (on a scale of 1-5). Based on JMA notices, the Tokyo VAAC reported that explosions during 22-28 April generated plumes which rose to altitudes of 1.5-4.9 km and drifted S, SE, E, NE, and N.

Tungurahua

Moderate-to-high seismic activity at Tungurahua during 22-28 April, characterized by long-period events, tremor, and explosions. On 28 April an emission with a minor ash content rose 3 km and drifted W. Roaring was noted and lahars descended the La Pampa (NW) and Rea drainages.

Popocatepetl

During 22-28 April the seismic network at Popocatépetl recorded 25-91 daily emissions mostly consisting of water vapor and gas. Cloud cover sometimes prevented observations of the crater, although gas plumes and nighttime crater incandescence were noted daily. On 22 April an explosion at 01.21 produced diffuse gas and water vapor emissions. Explosions at 16.43 and 17.58 local time generated ash plumes. The Alert Level remained at Yellow, Phase Two.

Krakatoa

PVMBG reported that during 1 March-21 April diffuse white plumes rose 25-50 m above Anak Krakatau, although foggy weather often prevented observations. Seismicity continued to be dominated by shallow and deep volcanic earthquakes, as well as signals indicating emissions. The Alert Level remained at .

Sheveluch

During 17-24 April the lava dome extrusion onto Sheveluch’s N flank was accompanied by incandescence, hot block avalanches, and fumerolic activity. A thermal anomaly was detected during 16-18 and 23 April; cloud cover obscured views on the other days. The aviation code remained at Orange.

Figure 1; http://fineartamerica.com/featured/halemaumau-by-moonlight-grant-kaye.html

Figure 2; http://news.yahoo.com/image-asia-pyroclastic-flows-erupt-mount-sinabung-121702289.html

Boxing Day Tsunami 2004 – 10 years on

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Very few natural disasters have effected the entire globe quiet like the events of Boxing day 2004. For me, it was one of the first that captured my full attention and left me wanting to understand how in a matter of minutes thousands of people can just be wiped of the face of the Earth.

The Setting.

The Indian Ocean lays on the western side of the Pacific Ring of fire where the Indio-Austrailian plate is subducting beneath the Eurasian plate along the Sunda trench. Tectonic activity such as earthquakes and volcanic eruption are everyday occurrence in the area. As plates move in relation to each other they can become ‘locked’, unable to move past each other. Over time stress can build up within the locked plate untill the stress can no longer be contained and snaps like a rubber band causing a massive release of energy in the form of an earthquake. This is known as a stick slip fault and is usually the cause of the most powerful earthquakes.

On December 26th 2004 this occurred in spectacular fashion along the Sunda trench. A magnitude 9.2 earthquake rocked the Indian Ocean at 7.58 am. Over an astounding 1600 km stretch of the trench, uplift was recorded to be on average 6 meters. This massive displacement of such a long length of sea bed thrust the ocean waters upwards as well causing tsunami waves which would travel round the world. Such a powerful earthquake is termed a megathrust and released the energy of over 1.1×1017 joules, which is the equivalent of 26 megatonnes of TNT or 1500 Hiroshima atomic bombs.

Despite its violent geology the area is a travelers paradise with millions flocking to the islands  year round. Its equatorial location means year round sun and therefore in especial popular as a Christmas destination. On Boxing day 2004 the beaches were filled you tourist from around the world blissfully unaware of the danger that loomed off the coast.

The Waves.

The first inclination that something was very wrong along the white sandy beaches was a process called draw back. As the earthquake thrusts water up directly above the epicenter water is pulled in from the local area to balance the displacement. From the local shorelines people could see the sea withdrawn quiet rapidly like low tide happening in very fast motion.

At the starting location the tsunami wave looks no more then a small bump on the surface of the ocean and travels at speeds of 500 – 1000 kilometers per hour. As is nears land and the sea floor rises up to the coastline as does the wave rearing up on its self; in this case in excess of 30 ft in places.

The Aftermath.

Over 275,000 people were killed in fourteen countries across two continents, with the last two direct fatalities being swept out to sea in South Africa, more than twelve hours after the earthquake. Scores more died in the coming weeks as decaying bodies and pollution made the spread of disease. Nearly 150,000 homes and buildings were destroyed by the waves.

Identifying bodies was near impossible new mortuaries had to be quickly constructed to handle the masses. In other cases some bodies took months to be washed up on shore and in others they were simply lost at sea.

Public response to the tragedy was unprecedented with over $14 billion US dollars raised by the public world wide, with about the same given by varying governments. It was by far not the worst or most fatal natural disaster in recent years but it touched the hearts of nations world wide at Christmas so every one flocked to help.

Different governments and agencies tended to stick to certain regions in the relief effort as seen above in a relief map produced by the Red Cross.

Road to recovery.

Now ten years on, the countries involved are well on the road to recovery but still scared by the events that Christmas. This years anniversary has seen coverage of the area rocket, with some stunning imagery showing how far certain areas have come since the devastation in 2004.

Will it happen again???

In short, yes. This was the not first major earthquake in this area now will it be the last. By January 1st 2005 there had already been 84 aftershocks ranging between magnitudes 5 to 7. On March 28th 2005 the biggest aftershock occurred just a few hundred kilometers from the original epicenter. Another tsunami was trigger but luckily waves of barely 10 ft were recorded in the local area, still 1346 people lost their lives.

With the tectonic location of the Indian Ocean and its islands, it is never a matter of ‘if’ but a matter of when such events will occur. What hinder this further is it is one of the most densely populated areas of the world but its equatorial weather and fertile volcanic grounds make it prime location for people to live regardless of risk.