What are the large, dark-colored, relatively flat regions of the Moon called?

• A. Highlands
• B. Maria
• C. Craters
• D. Rilles

Answer: (B)

On the Moon, the large, dark-colored, relatively flat areas are called maria. These are basaltic lava plains that filled large basins created by ancient impacts. When the lava cooled, it formed smooth, expansive plains that look darker than the surrounding terrain, giving them their characteristic appearance. The dark color comes from basalt rocks, which are richer in iron and magnesium compared to the lighter rocks of the highlands. These maria are mostly on the near side of the Moon and cover substantial areas, which is why they’re the prominent dark patches you notice. In contrast, the bright, rugged regions are the highlands, which are older and more heavily cratered. Craters are circular holes formed by impacts, while rilles are channel-like valleys that formed from ancient lava flow or crustal cracking.