How come bodies of water (lakes, rivers, wetlands, oceans even…) exist above ground instead of the water simply being absorbed by the earth?
In: 855
So dirt/mud, which is clay, silt, and sand. Is permeable. Water will sink into it. (And soil is just dirt with organic matter mixed in) so you pour water on it, water will sink into it. So how do ponds and lakes form? Well two ways. The first and most important. Is bedrock. Rock is typically not permeable. Limestone and sandstone are, but the rate at which water permeates is so slow it’s negligible. Igneous rocks, and metamorphic rocks are not permeable. So when the bedrock is made of one of those, water can drain down through the dirt until it hits rock and then it starts to pool, when the pooling gets above the dirt you get a lake or pond. This is also why water tables are at different heights and aren’t all just universally sea level.
The other way is saturation. The dirt can only hold so much water. And it can only diffuse it to neighboring dirt so quickly. So if you’re adding water to dirt faster than the dirt can absorb or pass it through then you’ll again end up with standing water. This happens a lot with rainstorms. But also some creeks and rivers work this way, at least partially or in some sections. Especially during floods.
Latest Answers