You might have noticed that icebergs and glaciers appear to be blue, but the ice in your freezer or on your sidewalk does not. 

The reason for this phenomenon is not exactly what you would expect, as you will see in this very interesting video. 

Watch as Joe Hanson, Ph.D. goes exploring in an ice cave under Alaska's Mendenhall Glacier to find the answers. 

Don't forget to leave a comment below to let me know what you thought about the video!