Today, at 10:57, Apple (symbol AAPL) had a whopper of a drop, with some systems (CNBC) showing a 9% drop, while my service (Think or Swim) is showing it dropping 1.3% from 598 to 590 . This was not a high volume dump of the stock - instead, it was a regular volume trade.
Some media reports, (CNBC for instance http://www.cnbc.com/id/46835129) are calling this a Flash Crash, and saying: Apple Flash Crash: Stock Halted After Trade Causes 9% Plunge.
My chart (see picture), which is showing data from "Think or Swim", shows a drop from 598 to 590, which is 8/598, or 1.3%. So, I don't know which report is correct, since the math appears to be different between the two systems.. Of course, the system I use for stock trading, Think Or Swim, may not have captured the whole move.
Also, I don't see any evidence that the stock has halted trading - have a look at the picture yourself - it's still moving around as I post this.
Anyway, here's the picture!