What is the difference between dunes and loess?

Answer 1

Sand dunes are made from mainly one mineral - sand or quartz grains and they form and move to develop a typical cross bedding structure.

Loess however is wind blown silt (a mixture of sand and clay) with a fine grain size typically in the 20-50 micrometer range. The deposits are typically non stratified and cover a wide area. They also quickly become loosely cemented after deposition and are not reworked as are sand dunes.

The source material for loess deposits is the rock flour left by retreating Ice sheets and the deposits therfore form in temperate regions while Sand Dunes are an indication of arid desert (tropical) conditions.

Answer 2

At its most basic level, the main difference between these two soil types is that alluvial material has been deposited by waterways (rivers, deltas, estuaries, floods, etc) whereas loess refers to deposits made by winds.

Alluvial takes its name from the Latin alluvium meaning "wash, or flood" and as a class are usually more fertile soils consisting of silt, sand, mud, and sometimes gravel or stones.

While the method of deposit differs, loess and alluvial are also dissimilar in that loess soils are mostly composed of silt and sometimes calcareous material - materials that are primarily or entirely made up of calcium carbonate, aka lime or chalk. Loess soils are quite permeable, usually yellowish-beige to grey in color, and can contain fossilized material.

(Loam is a term that is often mentioned when discussing these kinds of soils and refers to a material that is usually an equal balance of sand, silt, and clay, with perhaps less of the latter. This is considered to be the most ideal soil for plant growth as it can be crumbly and porous in texture allowing for variance in water retention as well as proper drainage. The presence of calcium in these soils is considered a benefit as it makes the earth less acidic.)

Answer 3

Glacially derived loess deposits are typically composed of silt-sized particles, clay, and sand. Sand dunes are composed primarily of sand-sized particles, most often of quartz.

Answer 4

Loess blankets a broad area; sand dunes are mounds or ridges

Answer 5

Loess blankets a broad area; sand dunes aer mounds or ridges.

Answer 6

Loess is characterized by being extremely fertile.

Answer 7

Loess is very fertile while sand is not