The following steps describe how sedimentary rock forms at the bottom of a river. which two steps involve erosion? a large rock breaks down into sediment. the water transports and deposits the sediments. the water also transports calcite and clay, which glue the sediments together. the upper layers of deposits put pressure on the lower layers. rock forms as the layers of sediment and glue compact and cement together.

Erosion is the gradual destruction of something by wind, water, etc.

A large rock breaks down into sediment involves erosion because it is being broken down by water (because it says the sedimentary rock is formed at the bottom of a river).
The upper layers of deposits put pressure on the lower layers also involves erosion because the upper layers are eroding the lower layers, making it possible for the layers to stick together.