Some incredible price action on the Monday open in New York as "sell at any price" orders by margin accounts having to raise cash collided with algorithmic trading. Blue Chip stocks like General Electric gapped 21% down (that's a swing in market cap of about US$50 billion!), only to recover those losses by mid morning. This was not unusual, a multitude of stocks, ETF's and even currencies exhibited similar price action. NZDUSD traded (very briefly) in the low 61 cents only to instantly recover back to 65 cents. Incredible volatility. The chart below shows about 5 minutes of trading in NZDUSD just before the NYSE opened on Monday morning. Normally the currency trades on a couple of tick bid/offer spread. This chart shows the NZDUSD trading in an orderly fashion from 0.6500 down to 0.6300 with the normal tight bid offer spread. Then all kinds of mayhem erupts and the spread balloons out to nearly 2.5 cents. The lowest price that traded was around 0.6130, within minutes it was back up at 64 cents.
This type of volatility and disorderly market (or worse) was evident across almost every listed stock - truly a mad time. The good news is that the market recovered to an orderly condition relatively quickly. Lots of mini flash crashes, but no major flash crash.