A depression may be a region of tectonic downwarping typically associated with a Subduction Zone and Island Arc . Fore-arc and back-arc Sedimentary Basin s fill with Sediment from an adjacent island arc, or from continental Volcanism and uplift.
A Valley is a type of depression usually carved by erosion.
An Oceanic Trench is a deep depression with steep sides located in the ocean floor. Oceanic trenches are caused by the Subduction (when one tectonic plate is pushed underneath another) of Oceanic Crust beneath either other oceanic crust or Continental Crust .
A depression may be a Pothole - either a simple roadway depression or a Fluvial erosional depression in a RiverStreambed , or area affected by coastal water currents.
