Agressive Fermentation

I am newer to brewing as this is the fourth batch I've done. The current batch I'm working on is an IPA using malt extract and steeped grains. About six hours after the wort was put in to the primary fermenter I heard the airlock pop off the carboy and hit the ground. I then put on the blowoff tube on the carboy and put the other end in a bucket with sanitizer water mix. What I'm wondering is why is this fermentation so agressive? This is the first batch I've brewed where I have had to use the blowoff tube. The temp in the room where the carboy is about 64 degrees. It's been almost 24 hours and its still bubbling strong in the bucket with sanitized water. Just wondering what could be causing this and if it is a good or bad thing?

It's a great thing. It means the yeast are doing their job. As for what causes it, I honestly don't know, but it has happened to me on a couple of different batches.