It looks like ETC suddenly gaining an upper hand over ETH in terms of volume. It would be interesting to find out if ETH can retain top position after upcoming hard fork.
A sudden increase in volume coupled with a fall in price is a bad sign. It means that people want to get out and are dumping ETC in the market. The direct effect of this is on the miners. It will certainly reduce their earn.
Might as well be that day traders went in and out.. short term fluctuations is the combination of many different interests so it is hard to decipher what they mean IMO. Still up roughly 5% since yesterday though.