Der Spiegel reports on the growling-ever-louder Indonesian Merapi volcano in an article titled: Geologists Warning of Mega-Eruption of Merapi.

The Merapi eruptions are becoming more violent – and the big bang could be just ahead. The Indonesian volcano has been spewing 800°C ash clouds for days.

A rough estimate indicates that there is three times more magma than what was ejected by the Indonesian volcano Tambora in 1815 – the biggest eruption in the last 10,000 years, which led to a cooling of the climate globally...(more)

And it looks like Iceland may have another eruption soon...(here)

More info...

Tambora

"the bright sun was extinguish'd... morn came and went--and came, and brought no day"
-Darkness by George Gordon, Lord Byron


The Eruption
On April 10, 1815, a series of eruptions began, culminating to the largest eruption in recorded history. The eruption lasted several days. It blew a chunk off of the mountain almost a mile wide. The volcanic column, after flying 40 km (25 miles) into the sky, returned to the ground, creating a huge pyroclastic flow of ash, pumice, and debris. The pyroclastic flow alone killed more than 10,000 people in its path. The ash that fell from Tambora travelled as far as 1300 km (800 miles) away.

When the pyroclastic flow reached the ocean, the debris created such a large displacement of water that tsunamis as high as 5 meters (16 feet) emanated out from the island. These tsunamis caused flooding, devastation, and death on many of the other Indonesian islands.

After the eruption was over, an estimated 100-150 cubic kilometers of ash and debris were said to have been ejected from the mountain.

The Year without a Summer

In 1816, the overal temperature on Earth, specifically in the Northern Hemisphere, lowered so drastically that it became known as the year without a summer. Weather was disturbed all over, with problems in Western Europe and the United States, as well as Asia. Monsoon season was affected, which is thought to also be tied to a cholera epidemic that year. In places like New England and Canada, frost was recorded in every month of the year, and snow fell in June. This phenomenon is known as global cooling.

The summer temperatures in 1816 averaged just a few degrees below normal, but as mentioned, it frosted throughout the summer. The highs were still close to 100 degrees Fahrenheit on some days. However, the cold spells, especially at night, caused massive crop failure and as a result, even more famine.