Lunar 100 – Object 34
Lacus Mortis is a complex, irregular crater‑like depression north of Mare Serenitatis, partly filled with basaltic lavas. Its floor contains both a prominent rille system and a large ridge, features that indicate a combination of volcanic flooding, tectonic extension, and structural collapse. Lacus Mortis is included in the Lunar 100 because it is a strange hybrid feature: a crater modified by mare lavas and later fractured by rille formation, illustrating multiple geological processes acting on the same terrain.