“US stock market authorities have been forced to suspend the futures market on the Nasdaq index.
Panicking traders have driven it down 5% - the maximum allowed under Wall Street rules before a circuit-breaker is triggered.”
http://www.theguardian.com/business/live/2015/aug/24/global-stocks-sell-off-deepens-as-panic-grips-markets-live
countdown to a meltdown