"something catastrophic"

Mount Merapi may be tip of the iceberg, so to speak. William Sargent has a piece in today's Boston Globe:

THE MERAPI volcano, currently exploding more forcefully every day in Indonesia, is located on the Sundra Arc, one of the planet’s most complex and dangerous geological areas. This is where two large plates of the earth’s crust, the Australian and Indian plates, are rapidly plunging down below the mini Burma plate to create the world’s deepest and most powerful earthquakes and the world’s largest and most dangerous volcanoes. Some scientists fear that something catastrophic may be brewing beneath the Sundra Arc.

...

But Merapi is not the only volcano now active on the Sundra Arc. Within the past few weeks there have been many more deep earthquakes and 20 other volcanoes have also become active. Indonesia is also home to the Lake Toba supervolcano, believed to be the largest explosive eruption to have occurred on our planet during the past 25 million years.