When Mt. Tambora in Indonesia erupted catastrophically on April 10 in 1815 it was by far the most powerful eruption in over 800 years. The previous record-holder was thought to be Baekdu on the Korean-Chinese border sometime around 969 AD. There were no geologists or seismographs or much else at the earlier eruption. Later (2013 after some years of forensic searching and analysis), the 1257 AD eruption of Samalas on Lombok island in Indonesia was judged to be more powerful that Baekdu.
A few other vulcanologists obsessed with the past and I were concerned when there was a cluster of earthquakes near the caldera (shown above and the small blue area in the middle below) earlier this year. Today, the lake covers 45 square kilometers (17 square miles), with dimensions of 7.5 km by 6.0 km (4.7 miles by 3.7 miles) with a maximum depth of 230 meters (750 ft). From the water temperature it is obvious that there is plenty of magma remaining.
Some of the earlier blog entries about Lombok