ESTUARIESAN ESTUARY IS WHERE A RIVER MEETS THE SEA OR OCEAN.

Estuaries are partially enclosed bodies of water where freshwater (water without salt) meets salty ocean water. Bays, inlets and ocean-flooded river valleys are all examples of estuaries.

Estuaries are divided into four types, depending on how they are formed

Coastal Plain Estuaries

These are formed by the sea level rising and filling an existing river valley. Examples of this are the Chesapeake Bay in Maryland and the harbour in Charleston, South Carolina

Tectonic EstuariesThese are caused by the folding or faulting of land surfaces. These estuaries are found along major fault lines, like the San Francisco Bay area in California.

Bar-built EstuariesThese form when a shallow lagoon or bay is protected from the ocean by a sand bar or barrier island. Examples of these are found along the Eastern Seaboard and the Gulf Coast of North America.

FjordsFjords are U-shaped valleys formed by glacial action. Fjords are found in areas with long histories of glacier activity, like northern Europe, Alaska and Canada.

HOW DOES THIS DIFFER FROM A DELTA?

RAISED VALLEY SIDES

The Lower Course of a river valley has been DROWNED by a rise in sea level or a fall in the land level

River mud flats

Mudflat at low tide

Mudflats are deposited by the tidal currents that are too weak to carry the river silt away

Most of today's estuaries formed because the sea level has slowly risen during the last 18,000 years, drowning

river valleys and filling in glacial troughs.

Englishman Estuary Vancouver