Chapter 30, Problem 15RQ

Why are most of the world’s deserts found in the area known as the horse latitudes?

To determine

The reason behind the fact that the world’s deserts are found in the horse latitudes.

Answer to Problem 15RQ

The reason behind the fact that the world’s deserts are found in the horse latitudes is that the crews of sailing ships sometimes used to cast the horses overboard to conserve water when their ships were becalmed in the high-pressure belts.

Explanation of Solution

The area of the sweltering doldrums rises to the boundary between the troposphere and the stratosphere, where it divides and spreads into north and south. By the time it has reached $30°\text{N}$ and $\text{30°}\text{S}$ latitudes, this air cools enough to descend towards the surface.

At sea, this descending air produces very weak winds. Early sailing ships were frequently stalled at these latitudes. As food and water supplies dwindled, horses on board were either eaten or cast overboard to conserve fresh water and reduce the load of the ship. Thus these regions are known as horse latitudes.

The cool descending air warms as it is compressed. A resulting high-pressure zone girdles Earth, creating a belt of hot, dry surface air. On land, these zones account for the deserts.

Conclusion:

Therefore, the reason behind the fact that the world’s deserts are found in the horse latitudes is that the crews of sailing ships sometimes used to cast the horses overboard to conserve water when their ships were becalmed in the high-pressure belts.