Mount Sinabung is a Pleistocene

Pleistocene

The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

-to-Holocene

Holocene

The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...

 stratovolcano

Stratovolcano

A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...

 of andesite

Andesite

Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...

 and dacite

Dacite

Dacite is an igneous, volcanic rock. It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite. The relative proportions of feldspars and quartz in dacite, and in many other volcanic rocks, are illustrated in the QAPF diagram...

 in the Karo plateau of Karo Regency

Karo Regency

Karo Regency is a regency of North Sumatra, Indonesia. It is situated in the Bukit Barisan mountains. In 2000, the regency covered an area of 2,127.25 square kilometres and according to the 2000 census it had a population of 279,470. 60.99% of the regency is forested. Its regency seat is...

, North Sumatra

North Sumatra

North Sumatra is a province of Indonesia on the Sumatra island. Its capital is Medan. It is the most populous Indonesian province outside of Java. It is slightly larger than Sri Lanka in area.- Geography and population :...

, Indonesia

Indonesia

Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

, 25 miles from Lake Toba

Lake Toba

Lake Toba is a lake and supervolcano. The lake is 100 kilometres long and 30 kilometres wide, and 505 metres at its deepest point. Located in the middle of the northern part of the Indonesian island of Sumatra with a surface elevation of about , the lake stretches from to...

 supervolcano

Supervolcano

A supervolcano is a volcano capable of producing a volcanic eruption with an ejecta volume greater than 1,000 cubic kilometers . This is thousands of times larger than most historic volcanic eruptions. Supervolcanoes can occur when magma in the Earth rises into the crust from a hotspot but is...

. Many old lava flows are on its flanks and the last known eruption, before recent times, occurred in the year 1600. Solfataric activities (cracks where steam

Steam

Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...

, gas

Gas

Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

, and lava

Lava

Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

 are emitted) were last observed at the summit in 1912, but no other documented events had taken place until an eruption in the early hours of 29 August 2010. With the 2010 eruption, Sinabung joins other, long inactive volcanoes such as Fourpeaked Mountain

Fourpeaked Mountain

Fourpeaked Mountain also known as Fourpeaked Volcano is an active stratovolcano in Alaska. The Alaska Volcano Observatory currently rates Fourpeaked as Aviation Alert Level Green and Volcanic-alert Level Normal. It is nearly completely covered by Fourpeaked Glacier. It was long a dormant volcano...

 in Alaska

Alaska

Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

 which have erupted in recent years.

Geology

Most of Indonesian volcanism stems from the Sunda Arc

Sunda Arc

The Sunda Arc is a volcanic arc that has produced the islands of Sumatra and Java, the Sunda Strait and the Lesser Sunda Islands. A chain of volcanoes forms the topographic spine of these islands...

, created by the subduction

Subduction

In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...

 of the Indo-Australian Plate

Indo-Australian Plate

The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and surrounding ocean, and extends northwest to include the Indian subcontinent and adjacent waters...

 under the Eurasian Plate

Eurasian Plate

The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia , with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia...

. This arc is bounded on the north-northwest by the Andaman Islands

Andaman Islands

The Andaman Islands are a group of Indian Ocean archipelagic islands in the Bay of Bengal between India to the west, and Burma , to the north and east...

, a chain of basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

ic volcanoes, and on the East by the Banda Arc, also created by subduction.

Sinabung is an andesitic

Andesite

Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...

-dacitic

Dacite

Dacite is an igneous, volcanic rock. It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite. The relative proportions of feldspars and quartz in dacite, and in many other volcanic rocks, are illustrated in the QAPF diagram...

 stratovolcano

Stratovolcano

A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...

 with a total of four volcanic crater

Volcanic crater

A volcanic crater is a circular depression in the ground caused by volcanic activity. It is typically a basin, circular in form within which occurs a vent from which magma erupts as gases, lava, and ejecta. A crater can be of large dimensions, and sometimes of great depth...

s, only one being active.

August 2010 eruption

On 29 August 2010 (local time), the volcano experienced a minor eruption after several days of rumbling. Ash spewed into the atmosphere up to 1.5 kilometre (0.93205910497471 mi) and lava was seen overflowing the crater

Volcanic crater

A volcanic crater is a circular depression in the ground caused by volcanic activity. It is typically a basin, circular in form within which occurs a vent from which magma erupts as gases, lava, and ejecta. A crater can be of large dimensions, and sometimes of great depth...

. The volcano had been inactive for four centuries with the most recent eruption occurring in 1600.
On 31 August, 6,000 of the 30,000 villagers who have been evacuated returned to their homes. In Indonesia the volcano was assigned category “B”, because it was not active for more than 400 years, which means it is not necessary for it to be monitored intensively. (Other volcanoes, in category “A”, must be monitored frequently). Surono, head of the Indonesian national volcanology and geology agency, says he plans to lift the evacuation order in a week or two if the situation does not change. The Indonesian Red Cross Society

Indonesian Red Cross Society

Indonesian Red Cross Society is a humanitarian organization in Indonesia. It is a member of International Federation of Red Cross and Red Crescent Societies.-History:The IRCS was created on September 17th, 1945, exactly 1 month after Indonesia’s independence...

 and the Health Ministry of Indonesia sent doctors and medicines to the region. The National Disaster Management Agency is providing thousands of face masks and food to assist the evacuees.

September 2010 eruption

On Friday 3 September, two more eruptions were noted. The first happened at 04:45 am in the early morning, forcing more villagers to leave their houses - some of them had just returned the day before. This eruption was the most intense so far, with ash spewed up into the atmosphere about 3 kilometres (1.9 mi) high. Some hours before the eruption a warning had been issued through the volcanology agency, and most villagers were prepared to leave quickly. A second eruption occurred the same evening, around 18:00 pm. The eruption came with earth quakes which could be noticed in a 25 kilometres (15.5 mi) distance around the volcano

On Tuesday 7 September, Mount Sinabung erupted yet again, its biggest eruption since it became active on August 29, 2010 and experts warned of more blasts to come. Indonesia's chief vulcanologist, Surono, said "It was the biggest eruption yet and the sound was heard from 8 kilometres away. The smoke was 5,000 metres in the air". "I think this will not be the last eruption. It will happen again," he said. Heavy rain mixed with the ash to form muddy precipitation that is lying a centimetre thick on buildings and trees. Electricity in one village has been cut off, but there have so far been no casualties.

Government response

The Indonesian government was reported to have evacuated around 17,500 people from the region on and around the volcano. The government issued the highest-level warning for the area, which was expected to remain in force for around a week, since scientists were unfamiliar with the characteristics of the volcano, due to it having been dormant for so long. The government also set up kitchens for refugees to have access to food and handed out 7,000 masks.
Over 10,000 people have been internally evacuated after the eruption, Secretary of the provincial administration, Edy Sofyan told Xinhua by phone. Spokesman of National Disaster Management Agency Priyadi Kardono said the eruption had not been predicted earlier like other volcanoes and that authorities must conduct a quick preparation for emergency work because Mount Sinabung’s seismic activity has been monitored intensively only since Friday after it showed an increase in activity.

Effects

The towns nearest to the volcano are Kabanjahe

Kabanjahe

Kabanjahe is a town approximately 2 hours from Medan, North Sumatra, Indonesia. Kabanjahe is to the south of Berastagi. Kabanjahe is the capital of Karo Regency. Frequent buses connect the two towns and a journey takes about 30 minutes....

 and Berastagi

Berastagi

Berastagi is a town and subdistrict of Karo Regency situated on crossroads on the main route linking the Karo highlands of Northern Sumatra to the coastal city of Medan...

. There were no disruptions reported to air services at the regional airport, Medan's Polonia

Polonia International Airport

Polonia International Airport is located in the city of Medan, Indonesia, about 5 km from the Central Business District. It is the first international airport in Medan, the other being the planned Kuala Namu International Airport...

. One person was reported dead due to the eruption; he had respiratory problems while fleeing his home.

See also

• Mount Sibayak – an active volcano near Sinabung