 I'd like to show you some examples of physical and chemical weathering with the same type of rock. So this is a photo, shows an example of physical weathering. And the bedrock itself is a shist. It's from New Zealand, the South Island. And it's a metamorphose sedimentary rock. And shist has cleavage planes in it, and those cleavage planes tend to break very easily. And so in this particular case, we had these flat surfaces in here, or the surfaces of some of those cleavage planes. And there's a trail here that I was walking on, and the trail had cut into some of the shist and these big pieces were broken off. And so you can see that there are lots of plants around. But when I looked at this rock close up, it had essentially the same mineralogy. These blocks had the mineralogy of the shist. It had the biotite and the feldsparas and quartz and all those things that are in the parent bedrock. And so in the case of the physical weathering, it was just breaking the blocks up, but not actually altering their chemistry. So in terms of the processes that influence the physical weathering, I think a lot of it was water flowing in between these cracks. I don't see any evidence of roots in them right here, but over here you can see some roots sticking out. So I think roots can help with that physical weathering process. And then because the cleavage of the shist made it so that there was a weak plane allowed gravity, the weak plane allowed gravity to pull these blocks down. These two images are along the same trail, and they show examples of chemical weathering. And the chemical weathering changes the composition of the minerals themselves. So this one has a lot of water and it was actually pouring rain for part of my hike there. And that water is filtering in under all the plants here, and the plants are providing organic acids. And those acids help dissolve the rock and alter it into different minerals. So within the water you have ions from the reactions of the water and or acids and rocks. And then this brown is a lot of clay minerals. There's still chunks of the shist here, so there's also physical weathering going on. But when this area that's really wet dries out, it's all powdery, like the image here. And the sediment here is a very, very fine grained and reflects those clay minerals. So we have possibly the dissolution of some minerals, but in general we have the alteration of the shist to clay, plus likely some quartz from the original shist, which doesn't alter very easily at all. And I should note that the red color here is probably from iron oxides. Thanks for watching.