marsh is a coastal marsh that forms on mud flats. They usually
form in very sheltered inlets and estuaries, or behind spits
(places where fine sediment accumulates). As vegetation builds
up on these mud flats salt marshes form.
Sand dunes are created
by strong winds and not by coastal erosion or deposition.
As sand is blown up a beach is forms small hills. These are
often rooted together by long-rooted grasses such as marram
grass. Marram grass is usually planted to reduce the erosion
of the otherwise unstable sand dunes.