# How is the windward slope different from the slip face?

## How is the windward slope different from the slip face?

windward – The side of a dune, mountain, or hill facing the wind. slip-face – The steep leeward side of a dune where sand falls as wind moves it over the peak.

In what direction do dunes generally move?

These winds are called unidirectional winds because they always move in the same direction, from the southwest to the northeast. As the wind blows, it pushes the sand ahead of it, so individual dunes are slowly moving to the northeast.

What is the slip face?

: the lee side of a dune where the slope approximates the angle of rest of loose sand that is generally about 33 degrees.

### Why is one side of a sand dune steeper than the other?

Viewed from one end, sand dunes have a flat back side and a steep front side. The wind blows up the back side of the dune. This process causes a sand dune to migrate down wind. Sand is continually eroded from its upwind side, and deposited on its downwind side.

Has a steep side called a slip face?

As on Earth, the downwind side of a sand dune has a steep slope called a slip face. Sand grains blowing across the windward side of a dune become sheltered from the wind by the dune itself.

What is the space between two Seif dunes called?

Dunes occur in different shapes and sizes, but most kinds of dunes are longer on the stoss (upflow) side, where the sand is pushed up the dune, and have a shorter slip face in the lee side. The valley or trough between dunes is called a dune slack.

#### Which side of a sand dune has the steepest slope?

downwind side
The side of the sand dune that faces the direction of the wind movement normally has a gentle slope, while the downwind side has a steeper slope. The downwind side of the dune is referred to as the slip face.

What is the slip face of a sand dune?

A dunes slip face is simply the side without wind. A slipface is usually smoother than a dunes windward side. A collection of dunes is called a dune belt or dune field.

Why do the horns on a parabolic dune face up wind?

Longitudinal Dunes: long, narrow ridges of sand parallel to the prevailing wind direction. They form where sand supply and vegetation are meager and winds are strong. Parabolic Dunes: Crescent-shaped with the steep slip face on the convex side so that the “horns” point upwind.

## What is the steepest side of a sand dune?

The steeper lee side of the dune, called the slip face, maintains a 34° angle (called the angle of repose), much greater than the flatter (10°-12°) windward side.

What kind of slope does a sand dune have?

All sand dunes possess a windward (gentle) slope, a crest, a slip face and leeward slope. The gentle portion of the dune is perpendicular to the direction of the prevailing winds.

Where does the slip face in a sand dune form?

The slip face, in crescent sand dunes, forms on the concave portion of the dune. They form where the prevailing winds blow in one direction. These types of dunes usually move very fast in deserts. Linear dunes are typically very straight dunes that can reach up to 150 km (94 miles) in length.

### Why do seif dunes have a meandering slope?

For angles between 40° and 90°, there is a gradual transition in the lee slope, from dominant erosion and transport to deposition. For that reason the linear seif dunes tend to meander (Figure 7) and consequently change the angle of incidence and the function of the lee side from an erosional to a depositional zone.

What kind of slope does a barchan dune have?

Migrating dunes such as barchan and transverse dunes have two distinct slopes, a moderate windward and a steeper leeward. The windward slope undergoes erosion and the sand is carried to the lee slope where it is deposited on the upper part of the slope. When the upper lee slope reaches the critical angle of internal friction, a failure begins.