It shows that the bulls have taken full control just like the big red line all the way to the left shows that the bears had taken full control im a beginner but in a nut shell thats what i believe it means Massive volume is confirmation. it needed to push past resistance 9k and the spike in volume validates the bulls took control and overwhelmed the bears, it comes from i believe more faith in the market people not as worried as before a change in attitude and outlook. Maybe someone with more knowledge will reply and give more insight as i said im a beginner but i believe that is why.
Its the CBOE expirations. There will be much more volatility today. I have been saying to the upside the later in the day. It was the downward spike last month about the same time with the very high volume. And dont forget CME expirations as well. They were that other spike you see about a week later. CME expires last friday of the month. I think this will move to almost 10K today.