Contact between Archimedes crater wall (bottom left) and floor (upper right). The floor is smooth and relatively flat compared to the sloped and rough elephant skin textured crater wall. LROC NAC M119883761, image width is 800 m [NASA/GSFC/Arizona State University].
Archimedes is an 83 km diameter crater located in east Imbrium basin (29.7° N, 4.0° W). Archimedes is notable for its smooth floor, but unlike othercraters with smooth floors, Archimedes is flooded with mare basalt. Craters with flooded floors are geologically important as they can establish relative ages of features thanks to the geologic law of superposition.
LROC WAC monochrome context image of Archimedes crater. The floor of Archimedes appears as smooth as Mare Imbrium! Arrow shows the location of the NAC image. Image width is 130 km [NASA/GSFC/Arizona State University].
Because both Archimedes and Imbrium basin are flooded by mare basalt, their formations must be older than the volcanic activity. Furthermore, because Archimedes is located within Imbrium basin, Archimedes must be younger than Imbrium. Just by studying relationships between features, scientists can piece together their history!
Explore more of Archimedes' floor in the NAC frame!