The number of earthquakes under Indonesian Banda Api volcano has sharply increased over the past couple of days prompting authorities to raise the volcanic alert level to 2. Preparations are currently underway to evacuate some 1 000 people living near the volcano. The last eruption of this volcano took place in 1988, killing 3 people.
The number of earthquakes started gradually increasing with the beginning of March and sharply increased on April 4, 2017, forcing the authorities to raise the volcanic alert and ban any activity within 1 km (0.62 miles) from the crater.
Indonesian disaster agency said that they have already mapped the area and warned that over 770 people are living within 1 km. All of them must be displaced as soon as possible, they said.
"We have issued a recommendation for evacuation. There must not be any activity in the area of one kilometer from the crater," head of the observation unit at the national volcanology agency Devi Kamil said. "Should the frequency of the tremor keep rising, an eruption may happen. But, if it doesn't, poisoned gas will spread from the crater," Kamil added.
Visual observations between March 28 and April 5, 2017, did not show any significant changes in terms of color and height of the smoke, the agency said. Increased activity under the volcano indicates the process of rock fracturing due to the movement of magma and the number of earthquakes recorded between April 2 and 4 suggests that this process is significant enough to produce an eruption.
Although the eruption might not occur at this time, earthquakes over the past several days are identical to those occurring before the 1988 eruption.
There are over 20 known historical eruptions of Banda Api, with the last one in May 1988. It was a major eruption which started at 06:30 WIT on May 9, producing a 3 - 5 km (4.8 - 8 miles) eruption column with a large burst of volcanic material from the crater.
The eruption was followed by lava flows into the eastern sector, toward Banda Neira. It gave clear pre-eruptive signals, both visual and seismic.
The 1988 eruption had volcanic explosivity index (VEI) of 3 and it lasted 8 days. Three people were killed and over 1 000 others evacuated.
The small island volcano of Banda Api is the NE-most volcano in the Sunda-Banda arc and has a long period of historical observation because of its key location in the Portuguese and Dutch spice trade. The basaltic-to-rhyodacitic volcano is located in the SW corner of a 7-km-wide mostly submerged caldera that comprises the northernmost of a chain of volcanic islands in the Banda Sea.
At least two episodes of caldera formation are thought to have occurred, with the arcuate islands of Lonthor and Neira considered to be remnants of the pre-caldera volcanoes. A conical peak rises to about 600 m at the center of the 3-km-wide Banda Api island. Historical eruptions have been recorded since 1586, mostly consisting of Strombolian eruptions from the summit crater, but larger explosive eruptions have occurred and occasional lava flows have reached the coast. (GVP)
Featured image: The 640-m-high symmetrical volcano of Banda Api, the most active of a chain of volcanoes in Indonesia's Banda Sea, forms a small 3-km-wide island within a largely submerged 7-km-wide caldera. This May 19, 1988, view from the south shows vegetation damage from the 1988 eruption and the southern half of a prominent arcuate fissure that extended from the south coast through the summit to 200 m above the north coast. The still-steaming narrow black lava flow entering the sea to the left of center is one of four erupted in 1988. Credit: Tom Casadevall, 1988 (U.S. Geological Survey).