The British Parliament passed a law granting independence in July 1947. The law gave people only one month to decide which country they wanted to live in and to move there. As millions of people began to move, more violence broke out.
Calderas form when an enormous magma chamber under, what was probably a pretty ginormous volcano, empties and collapses, causing the land above it to collapse as well. An explosive caldera-forming eruption has never been witnessed first hand, but we know that they should pretty fearsome spectacles. Much smaller calderas atop effusive volcanoes (hawaiian style) have been observed. So, formation: maars form when a vent intersects groundwater and blasts out the overlying material.
It's when we go into the geological record that we come across the real sleeping giants, the so-called super-volcanoes or explosive calderas. The last to erupt was the Toba volcano in Indonesia some 73 thousand years ago.. It had a VEI of 8 and is the largest known eruption on Earth in the last 25 million years.