Debris Line, Deflation, Degradation, 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 debris line, deflation, degradation, and delta.

Debris Line
The English word debris comes from French débris, from Middle French débris, from debriser ("to break to pieces"), from Old French debrisier, a combination of de- ("away, from") and brisier ("to break").

Debris denotes anything broken down or destroyed.

In geology, the word is applied to any accumulation of loose material arising from the waste of larger material, especially rocks but also vegetable or animal matter.

On a coast, a debris line is a line marking the limit of debris deposits on a shore, that is, the highest point of deposits from the uprush of waves during storms.

Deflation
The English word deflation in its geologic sense comes from Latin deflatus, the past participle of deflare ("to blow off"), a combination of de- ("away, from") and flare ("to blow").

Deflation is the erosion of soil by wind. Specifically on a beach, it is the removal of loose, light material by wind action.

Degradation
The English word degradation comes from Late Latin degradation-, a combining form of degradatio, from degradatus, the past participle of degradare ("to degrade"), a combination of de- ("away, from") and gradus ("grade").

The original meaning of degradation applies to people and means a lowering in rank, or grade.

In geology, degradation denotes a wearing down by erosion. Specifically on a coast, it is the process by which natural features are worn away and their general level lowered by the action of wind and water.

The term is often used in discussions with its opposite: aggradation, a building up of natural features by the process of depositing materials.

Delta
Modern English delta comes from Middle English deltha, from Greek delta, of Semitic origin. The word is akin to Hebrew daleth ("daleth," the fourth letter of the Hebrew alphabet, from deleth, "door").

The original meaning of delta is the fourth letter of the Greek alphabet. In its capital form, the letter looks like a triangle. Therefore, something with a similar shape is also called a delta.

The most common use of the word delta is to denote the triangular alluvial deposit at the mouth of a river. Such a deposit tends to develop in coastline areas where no tidal or current action can remove the sediment as fast as it is deposited by the river.

A tidal delta is a similar deposit made by tidal currents at the mouth of a tidal inlet.

A wave delta is produced by the deposits of large waves running over any of various coastal features, such as barrier beaches (high offshore sandbars).
_____________________________

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.