We have studied the Marius Hills region and mapped the spectrally distinct flows present for the first time, using photographic and Clementine multispectral data. The basalts on the plateau are varied in age and composition but are dominated by a high-titanium Eratosthenian basalt, most likely from the same source as the Flamsteed Basalt, further south. The thickness of the basalts across the plateau is consistently greater than 120 m and is considerably thicker in some areas. A lower limit of 5320 km3 of basalts has been erupted onto the plateau. The domes and cones in the region do not appear to be related to any specific basalt or volcanic episode but occur at all levels in the stratigraphy that can be derived in the region. The eruption conditions required to form these constructs indicate that they must represent a series of separate volcanic episodes occurring throughout the history of the plateau. Cones on the Marius plateau are dominated by a strong glassy signature and often have an associated microlitic structure. Examples are shown of localized microlitic or glassy materials in regions where no cone is evident in the photographic data. These features are proposed to represent short-lived pyroclastic episodes that have deposited glassy and microlitic units on the plateau but have not been maintained for long enough to develop a cone. The volcanic history of the Marius Hills region is extremely complex, and most likely involved several separate episodes of volcanism with a large contrast in eruption styles and characteristics.