Mare Crisium 17.0°N, 59.1°E
Mare Crisium, ‘Sea of Crises’, is, like all lunar maria in the central region that are flooded with lava from the mantle, a significantly larger impact basin with several basin walls (a multi-ring basin). The area of the lava-flooded portion of the basin is, at 180 000 km2, comparable to the area of England. Mare Crisium extends about 560 km in the east—west direction and about 420 km in the north—south direction. Because of foreshortening of perspective at the limb, however, the north—south extent appears greater. In comparison with the other maria, the lava is relatively dark. The basin arose in the Nectarian era on the lunar timescale, so the age of the impact is about 3.92 × 109 years. Flooding with mantle lava took place much later, and possibly in several successive episodes. The walls of the basin have an average height of 3 km above the surrounding surface. Mare Crisium is, like all of the other maria, the site of a mascon, a gravitational anomaly in the overall gravitational field.
Under grazing illumination, a concentric system of low mare ridges is visible around the outer perimeter of the lava surface. The most conspicuous sections are Dorsa Harker and Dorsa Tetyaev, in the eastern section of Mare Crisium, with lengths of about 180 km and 200 km, respectively. On the western side, Dorsum Oppel stretches for about 300 km. The wrinkle ridges approximately follow the curvature of the edge of the mare.
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