Huge blocks of shares in last hour

[Palm]

Seems like we've had this before.  In the last hour there have been some huge blocks of shares (2 at just over 200k and 2 at just over 70k) traded which took our volume from the mid-600k level to well over 1 million.  PPS went up some but just .40 - .50.  Can someone much smarter than I explain what this appears to be.  Like I say, seems like someone explained it once before as maybe option activity or something. And now (at 3:05 on CNBC it shows volume back just under a million shares.

[CesiumFormate]

Seems like we've had this before.  In the last hour there have been some huge blocks of shares (2 at just over 200k and 2 at just over 70k) traded which took our volume from the mid-600k level to well over 1 million.  PPS went up some but just .40 - .50.  Can someone much smarter than I explain what this appears to be.  Like I say, seems like someone explained it once before as maybe option activity or something. And now (at 3:05 on CNBC it shows volume back just under a million shares.

It has to be a Dark Pool to trade that kind of volume and not impact the share price.

[jft310]

Its called a limit order. Example. Heres what you say to the the trading desk. I will buy 100,000 shares of IOC at $76.50 or below. They cross the trades from the seller the shorts maybe to the long. But its called stealth accumulation. The trading desk literally call up the people they know that have shares on either side and get an order executed cause that how they get paid off the spread.

[ArtM72]

Reading a bit about dark pools suggests to me those would provide a very logical explanation especially in that only trading summaries need to be reported, not individual transactions.