Geologically, the area of modern Indonesia appeared from under the Southeast Asian seas as the result of the Indian and Australian plates colliding and slipping under the Sunda Plate, sometime in the early Cenozoic era around 63 million years ago. This tectonic collision created Sunda volcanic Arc that has produced chains of islands of Sumatra, Java and the Lesser Sunda Islands. The active volcanic arc creating supervolcano that today become Lake Toba in Sumatra. The massive eruption of Toba supervolcano that occurred some time between 69,000 and 77,000 years ago (72,000 BC) instigated the Toba catastrophe theory, a global volcanic winter that caused a bottleneck in human evolution. Other notable volcanoes in Sunda Arc are Mount Tambora (erupted in 1815) and Krakatau (erupted in 1883). The region is known for its instability due to volcano formations and other volcanic and tectonic activities as well as climate changes; resulted in lowlands drowned occasionally under shallow seas, the formation of islands, the connection and disconnection of islands through narrow land-bridges, etc.