October 23, 2017
For this week’s picture, here’s an image of a relatively young basaltic surface weathering. You can see yellow-green olivine crystals weathering out of the dark matrix. Olivine is one of the first minerals to weather out of rocks, so you can tell that these basalts must be young. Older basalts generally don’t contain fresh olivine, at least not any crystals that you can easily identify with the naked eye. I took this picture back in March on Réunion Island, a young volcanic island in the Indian Ocean.