Just thought I'd share some scenic photos from my trip to the Cook Islands last year. The first was taken on the way up Mt Raemaru while the second was taken on the Cross Island Trek.
Well, I don't really know. The grooves appear to be the result of tree roots, as there is still a root in the photo that appears to be following a groove in the rock... This doesn't make much sense if you know that rocks are generally harder than tree roots (and of course the root could just be following a pre-existing groove). However, the island of Rarotonga was formed as a result of volcanic activity and is full of volcanic rock which is generally porous and prone to erosion. Also, the island of Rarotonga is a very wet place, receiving 4,000 mm of rain per year. Its plants are very happy plants. Though I can't describe a precise geological explanation, I have a feeling that the tree roots caused those grooves in the rock. That's my best guess anyway. I'd love to know the scientific explanation.
