You will see big volumes when a price becomes attractive to the buyers or vice versa. This is due to the price range which is attractive for the Bulls o Bears and they are not hesitant of getting in the position. When these market orders comes in picture, you will see a drastic/ surprising increase in buyers and sell and the candles will head south ways.
It all depends on where the big volume candle has appeared. You have to see if the big volume candle has happened at the start of a move or after the price has already moved much. If the price has already moved a long way and then a big volume candle appears it could signify “End of Move” and the market could retrace or even reverse from there as the sellers will overwhelm the buyers and vice versa.
@ kishy I can see what you are referring to, there is an easy way to identify this. You can take this as a final blow from bears or the bulls (Who so ever are losing).
You referring to Marubozu, which is itself a indicator candle for Trend reversal. This candle will have no shadows and will only cost of Body. You always see a Dozi or spinning top before this candle.