On a weather map, which feature indicates an occluded front?

• A. Purple line with alternating triangles and half-moons
• B. Dashed line
• C. Blue line with triangles
• D. Red line with semicircles

Answer: (D)

Occluded fronts form when a cold front catches up to a warm front, merging the two boundaries into one. On weather maps, this boundary is shown with a purple line that carries both cold-front and warm-front symbols—alternating triangles and semicircles along the line. The purple color signals the combination, making it clear this is an occlusion rather than a purely cold or purely warm front. The other symbols correspond to different fronts: a blue line with triangles is a cold front, a red line with semicircles is a warm front, and a dashed line by itself doesn’t indicate an occluded front.