Memnonia occurs on the western margin of the Tharsis volcanic province and on the southern margin of Amazonis Planitia. Its elevation ranges from a few kilometers above datum in Terra Sirenum to a few kilometers below datum along the northern edge of the map sheet. The cratered and faulted terrain of Terra Sirenum gives way to Tharsis lava flows to the east within Daedalia Planum. Valleys and channels mark the northern margin of the highlands, where they grade into low regions interrupted by elongate plateaus like Amazonis Mensa and the broader Lucus Planum.