Looking for long, free field recordings

For a while, I've been looking for high quality field recordings. Even generic ones like wheat fields or a waterfall. I'm really looking for long recordings, 10 minutes to an hour. Can you guys help with this?

Here's an example of what I'm looking for, but in video form:

http://www.youtube.com/watch?v=GqntA0XsWg8

I'm also really interested in finding good recordings of glacial calving:

http://www.youtube.com/watch?v=hC3VTgIPoGU

Here's one I found, but it's much too short:

http://silentlistening.wordpress.com/2008/05/09/dispersion-of-sound-waves-in-ice-sheets/

http://archive.org/search.php?query=field%20recording

And maybe you could source from movies/documentaries?