What is calving?

So, do you know what calving is when it is in reference to Alaska?  Well, I do, and boy is it awesome!  Go check out this video and see if you agree.  http://www.youtube.com/watch?v=ddymllsBuDg
Wouldn't that be something to see?  Alaska is an amazing place of beauty and wonder.  I haven't been there, yet, but will be going next June 2012, and I have to say, I Can't Wait!!  I will be taking a 7 night cruise up and back.  I am looking forward to seeing the beauty of what the Lord has created for us to enjoy.  There is so much to see and do I don't know where to begin.
You can bet that when I return I will write a full report.
If you've been to Alaska share your experience with me and others.