Hi Chasleo,

All good questions and each of the things that you have listed here are possible reasons that the volume in a particular instrument could spike.

For day traders the answer to the question of what caused the volume spike can be an important one. In order to ascertain this many traders will watch their level two quote screens to see what information shows that that can help them answer this question.

For longer term traders it is not normally so important what caused the spike than the fact that there was a spike and whether or not this should factor into their trading. The may way in which it does normally I would think is by showing how much participation or lack thereof there was in a move.

Hope that helps.

Best Regards,
Dave