Black smoke ring over Santa Clara
by Rob Beschizza from on (#572T4)
This video shows a black smoke ring floating over Santa Clara, California. What do you think caused it?
Perhaps more troubling for San Francisco football fans, it wafted over Levi Stadium, home of the seemingly doomed 49s.Here's another one from Denver, last year, attributed to "the pyrotechnics used during a Supercross event at Mile High Stadium."