How does water erode obsidian?

Water erodes obsidian primarily through a process called mechanical weathering, where the physical forces of moving water, along with sediment and other materials it carries, gradually wear down the glassy volcanic rock. Over time, the constant flow of water can create small fractures and chips in the obsidian's surface, leading to its breakdown. Additionally, chemical weathering can occur when water interacts with minerals in the obsidian, though this is less common due to its low reactivity. Overall, the combined effects of physical and chemical processes contribute to the erosion of obsidian by water.