As solid as granite?

Posted On October 31, 2010

People often refer to granite in ways that suggest its solidity, its permanence. In terms of a human life span that may be true but it’s interesting to see how granite reacts to the forces of Nature in the long term.

In response to the photo of a balancing rock in my post about the Tutshi River a few days ago, a friend in New Zealand sent me some photos of the Granite Arch in Girraween National Park in Queensland, Australia.

This final photo of an interpretive sign sent me on a search for more information about Girraween and about eroding granite. It says that among the forces that transform huge granite sheets and boulders into smaller ones that sometimes do the balancing acts that intrigue me, is lichen.

At the Girraween National Park Web site I found this document (now gone) that does a good job of explaining the forces that have acted on the granite there. In the Yukon we also have glacial erratics, which are rounded boulders left behind by retreating glaciers – which to me are indistinguishable from the weather-and-lichen eroded ones. All very interesting – thanks, Marie!