Located at ≈ 310°W and 12°N, Loki Patera (Plate 11a) is Io's most powerful and most intriguing volcano and one of the most prominent features on Io. Loki Patera appears as a low-albedo (and, by inference, relatively hot), sub-circular feature more than 200 km in diameter. A feature that looks like an “island” or “raft” takes up ≈25% of the area of the patera. This “island” is fractured, and pieces appear to have broken off in a manner akin to the calving of a terrestrial ice shelf. The “island” feature did not change appearance in the years between Voyager and Galileo so it is almost certainly immobile. It is likely to be either a resurgent dome (similar to that found in the terrestrial Long Valley Caldera) or possibly even a foundered mountain block (T. V. Johnson, pers. comm., 2005). The appearance of the Loki Patera region changed between Voyagers 1by the time of Galileo, looked very similar to its appearance as see and 2 (Smith et al., 1979c) but, n by Voyager 1, another indication of Io's tendency to exhibit long-term surface color and albedo stability (McEwen et al., 1998a). Additionally, the eruption mechanism at Loki Patera – the manner in which considerable volumes of lava yield their heat – has to maintain this appearance.

Loki Patera is therefore something of a paradox, showing little visible change while undergoing a high level of volcanic activity.