Dune, Duration, Ebb, Ebb-and-Flow Structure, Ebb Tidal Delta: Word Origins, Descriptions of Coastal Features, Processes

In the current alphabetic series of word origins and physical descriptions of coastal features and processes, here are dune, duration, duration of fall/rise, ebb, ebb and flow, ebb-and-flow structure, ebb current, ebb strength, ebb tidal delta, and ebb tide.

Dune
The coast-related English word dune goes back through French and Old French to Middle Dutch dune. The word is akin to Old English down ("hill").

A mound or ridge of sand deposited by wind action along a shore is a dune. Dunes are often stabilized by vegetation. A similar structure formed by sediment deposits on a seabed is also called a dune.

A duneland is an area having many dunes.

Duration
Wave forecasters use the word duration to denote the length of time the wind blows in the same direction over the wave-generating area.

Duration of Fall, Duration of Rise
The duration of fall is the time interval between high water (the maximum height reached by a rising tide) and low water (the minimum height reached by a falling tide).

The duration of rise is the time interval between low water and high water.

These time intervals constantly vary because of the moon's changing position and other factors.

Ebb
Modern English ebb comes from Middle English ebbe, from Old English ebba. The word is akin to Middle Dutch ebbe ("ebb") and Old English of ("from").

The ebb is the flowing back of the tide toward the sea. The term is used to mean both the period when the tide level is falling and the current that occurs during this period.

Ebb and Flow
The entire tidal process of ebbing and flooding is often referred to by the expression ebb and flow.

Ebb-and-Flow Structure
An ebb-and-flow structure is a stratified rock formation characterized by alternating layers believed to be produced by tidal ebb and flow.

Ebb Current
Ebb current, or simply ebb, is the movement of a tidal current away from shore.

Ebb Strength
Ebb strength is the ebb current when it is at maximum velocity.

Ebb Tidal Delta
A bulging sand formation caused by the interaction between waves and tidal currents at the mouth of a tidal inlet is called an ebb tidal delta.

Ebb Tide
The tide while ebbing is nontechnically referred to as an ebb tide.
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Encyclopaedia Britannica Ready Reference 2004. CD-ROM. Encyclopaedia Britannica, 2004.

Merriam-Webster's Collegiate Dictionary. 11th ed. Springfield, Mass.: Merriam-Webster, 2006.

Merriam-Webster's Geographical Dictionary. 3rd ed. Springfield, Mass.: Merriam-Webster, 2007.

The Oxford English Dictionary. 2nd ed. Oxford, England: Clarendon Press, 1989.