I am ashamed to admit that all this time -- I've been in a dilemma about which continent Greenland is a part of! Is it North America or is it Europe?

I took a look at my atlas (Orient-Longman) today; it shows Greenland along with the maps of North America.
Also, from what I see, the distance between Greenland and one of Canada's northern-most islands (Ellesmere Island) seems like just 20-30-odd kilometres! On the other hand Iceland (Europe) appears to be at least 500 kilometres away!
However, Greenland, being a part of Denmark should be classified as a part of Europe. (Or should it? Even though it's a big hunk of land, should it be treated like other dependent territories?)
What does everyone else think? What is the more established classification?