Where may the most favorable type thermals for cross-country soaring be found?

• A. Along thermal streets (thermal power lines)
• B. Over open water
• C. In forests
• D. On flat, featureless plains

Answer: (A)

Thermals are rising columns of warm air that gliders can climb in. The most favorable type for cross-country soaring are the long, continuous lines of lift you can ride along, called thermal streets. These form where the ground heats in a narrow, linear zone—think about places like roads, bare fields, or areas with heat sources such as power lines. The sun heats the ground along that line, and the resulting convection creates a chain of updrafts that you can follow from one thermal to the next, giving you a smoother, longer path of lift and the potential for a faster, more efficient cross-country run.

Open water tends to produce weak or inconsistent lift because there isn’t the same kind of surface heating pattern to organize updrafts. Forests break up and suppress convection due to the canopy, so lift is patchy and unreliable. Flat, featureless plains don’t provide strong, organized heating patterns, so lift is often weaker and harder to follow. That’s why the linear, heat-formed streets along features like power lines offer the best chance for sustained, rideable lift.