 Sediment transport is the key to understanding sedimentology and stratigraphy. And the main force that erodes mountains and creates sediment and deposits in low areas is liquid water. And that's because water is very efficient at transporting grains. We also have water in the solid form, ice. It does flow, it does have some viscosity. But the behavior of ice is very different than the behavior of water. And when I say water, I mean liquid water. Air is also important. And that, the air can pick up grains, they aren't as large and it's not as efficient as the transport by water or ice. Air is the main transport mechanism on Mars today. And then we also have what we can call gravity flows. And those are mixes of sediment and a fluid. It can be water, air, or ice that basically fall down the slope as a mix of different things. So this is fluid plus sediment flowing. And these are things like landslides, mud flows, pyroclastic flows are sometimes part of those as well. So the most important process on earth is water. And the behavior of that water, the flow speed, the flow depth, and the characteristics of the surface it's flowing over really affect how much sediment is transported. So we're going to spend quite a bit of time in the next few videos talking about the behavior of water and how it influences sediment transport. Thanks for watching.