There are several artists working in an almost unclassifiable genre sometimes called "land art," "earthworks," or "earth art." Land art involves working with natural materials, outside. Some "pieces" are very large, for instance using thousands of rocks to create a man-made jetty. But many current practitioners work on a much smaller scale, crafting boxes out of leaves or stacking rocks into precise shapes. The pieces are often sculptural in nature, but the most defining feature is that they are placed out in the open, left to change and erode under natural conditions.
One of the foremost practioners is Andy Goldsworthy, and the Library has several books and videos that highlight his fascinating work.
Another practitioner is a lesser known artist named Richard Shilling. The Library doesn't have any of his publications, but I've been following his Flickr stream and his blog. He's just announced a new project, a website titled "Land Art for Kids," which I think is brilliant. As he says, "land art is the perfect activity for kids and adults alike. What could be better than something that gets you active and creative, outdoors in the fresh air experiencing and learning about nature and discovering all you can about this wonderful world we share." He provides examples, instructions, and inspiration on the site, with more content on the way. (You can help create content, possibly, by sharing accounts and photos of the art your kids come up with.)
Sounds like the perfect way to spend time with kids on sunny, crisp November days!