Sinabung volcano (Sumatra, Indonesia): lava lobe destroyed, but dome growing bigger; nearby Super volcano Toba showing signs of activity. (VolcanoDiscovery).
The lava dome at the volcano's summit continues to grow at a rate of approx 100,000 cubic meters per day. Small to moderate pyroclastic flows during the past week have mostly removed the viscous lobe on the upper southeast flank.
As lava continues to accumulate at the dome itself, more pyroclastic flows are likely to occur in the near future. Authorities are considering extending the exclusion zone in the southern sector.
The alert level of the volcano was again raised from "siaga" to "awas", the highest on the Indonesian 1-4 scale. The reason is a currently elevated risk of possibly larger pyroclastic flows, that could be triggered by collapse of the increasing volume of the viscous lava lobe emplaced on the upper SE flank.
The alert level of the volcano had been at 4 during late Nov 2013 until April 2014,- the first and so far most violent phase of pyroclastic flow generation after the lava had spilled over the summit crater and built a large lobe that reached the base of the cone.
In addition to the large eruption at Mount Sinabung, we now have other reports that the nearby Toba supervolcano is showing large emissions of steam (from the ground), as well as foul smelling gas.
According to reports from Indonesian press, locals are alarmed by these recent developments.
Toba supervolcano is indeed a “super-volcano” by all measurements. Actually LARGER in eruptive power to the other more well known “Yellowstone” super volcano (located in Wyoming / United States).
Worthy to note, the Toba caldera produced the worlds largest eruption in the past 2 million years, and has not showed eruptive signs in over 75,000 years.
Toba is located near the Sumatra Fracture Zone (SFZ). Stratovolcanoes in Sumatra are part of the Sunda arc. Volcanism is the result of the subduction of the Indian Ocean plate under the Eurasian plate.(See pic left).
From Oregon state University:
The caldera probably formed in stages. Large eruptions occurred 840,000, about 700,000, and 75,000 years ago. The eruption 75,000 years ago produced the Young Toba Tuff. The Young Toba Tuff was erupted from ring fractures that surround most or all of the present-day lake. “
quote volcano discovery:
“About 74,000 years BP, more than 2500 cubic kilometers of magma were erupted. The eruption led to the final formation of one of earths largest calderas, the 35×100 km wide Toba caldera. Eruptions of this size are exptremely rare and are called supervolcano-eruptions. T
The Toba caldera is in fact the Earth’s largest Quaternary caldera.
It was formed during four major Pleistocene ignimbrite-producing eruptions beginning at 1.2 million years ago and culminating with the colossal Young Toba Tuff (YTT) eruption about 74,000 years ago. The YTT emplaced about 2500-3000 cu km (dense rock equivalent) of ignimbrite and airfall ash from vents at the NW and SE ends of present-day Lake Toba.” Hmmmm...........You know that long planned holiday...Maybe now is a good time to take it.