 Delta's form, where rivers flow into a standing body of water, like the ocean or lakes. The sediment is transported in the channels in rivers and they have a very narrow geometry and fast flow. When those channels interact with the standing water in the lake or the ocean, the flow speed slows down very quickly and that sediment is deposited. Now the geometry of that deposition is controlled by the amount of sediment in the river and the sediment transport processes in the ocean that they're flowing into. When there's enough sediment in the river to cause the shoreline to migrate into the ocean or lake through time, that's when you tend to form a delta. So the depositional environments on a delta vary depending on their location relative to the river and the ocean water. So we have here a delta top, often called a delta plane, and then this zone in here is the delta slope and that slope is determined by how much, how the sediment gets transported from the mouth of the river down the slope. Then out here we have what we call the pro-delta environment and this is where you have deep water and it's the furthest limit from the river mouth where the supply of sediment from the river is influencing the delta. So the pro-delta has just a small, very small influence from the river sediment. So there are different processes that happen in each one of these environments. On the top of the delta or the delta plane you have mostly river facies deposited, you have river channels and levees and floodplains, but the top of the delta is almost always at the same height as the sea level and so you often get a lot of lakes or bays in this zone here and that topography means that the rivers are usually meandering. So here we have meandering river facies for environments plus lots of lakes if they're freshwater or bays if they're saltwater. Then we have this really interesting place where the rivers intersect the ocean and these are the river mouths and if we look at that in detail what happens is you go from our channel into a standing body of water here. So I'll draw the water in blue. So this is right through a channel and then we get into the standing water. So this is a river channel. So here the flow is moving in this direction and here the flow speed is about zero. So what happens right at this river mouth is that you accumulate a huge amount of sediment right in that zone here where the flow speed has this biggest change in flow. And then it gets transported down the slope by waves or tides or turbidites depending on the detail of what happens. But often right at the river mouth here you have very high deposition rates and often things like climbing ripples and other sedimentary structures that really show very, very rapid sediment accumulation. So that's right at this river mouth and then on the delta slope there are various transport processes that move the sediment down slope. So the average direction of sediment is down slope deposition and that can occur with storms and waves with tides or if neither of those are enough the slope can build up steep enough that you end up with turbidites. And then right at this in the pro-delta area usually the types of things that you get out here are either distal storm deposits or distal turbidites out in this zone. So there's a very distinct sequence of environments and transport processes that create those variations in sedimentary structures that you see along a delta front. Thanks for watching.