* Wind Direction and Dune Formation: In deserts, the prevailing wind direction is a major factor in how dunes form. The wind erodes sand from the windward side (the side facing the wind) and deposits it on the leeward side (the side away from the wind). This creates a characteristic dune shape.

* North to South Wind: If the wind blows predominantly from north to south, the north side of the dune will be the windward side, and the south side will be the leeward side.

* Dune Shape: The leeward side (south side in this case) will be the steep slope. This is because the wind deposits sand on the leeward side, creating a gradual, sloping deposit. The windward side, facing the wind, will be more gently sloped.

In summary, a dune in a desert with a predominantly north-to-south wind will have a steep south-facing slope.