On the Valley of Death Cannon Protection System

http://scienceray.com/earth-sciences/geology/scientists-prove-ancient-alien-cauldrons-in-siberia-are-real/#ixzz20M6Q5mtq
http://www.theinsidegeek.com/2011/10/hidden-mysteries-the-cauldrons-of-tiberias-valley-of-death/

In Siberia, there lies a system of cannons whose purpose is to blow up any asteroids or comets that come dangerously close to Earth.  It used to only activate every century or so- as in the Tunguska and Vitim events- but has been attacking increasingly often due to the abundance of missles launched by humankind- such as in the case of the 1991 nuclear test that exploded with power 20-30 thousand times over predicted.

http://en.wikipedia.org/wiki/Vitim_event
http://www.youtube.com/watch?v=2PnfIL6WmGM