The explosion was probably caused by the airburst of an asteroid or comet 5 to 10 kilometers (3-6 mi) above the Earth's surface. The energy of the blast was later estimated to be between 10 and 20 megatons of TNT. It felled an estimated 60 million trees over 2,150 square kilometers (830 sq mi). An overhead satellite view centered at 60.917N 101.95E (near ground zero for this event) shows an area of reduced forest density, with a fully visible irregular clearing of somewhat less one square kilometer in area.