Hadriacus Mons by a contact between magma and groundwater. "Hadriaca Patera", a term formerly used for the entire edifice, is now only used for the central caldera, which is in diameter. Hadriacus Mons Hadriacus Mons is an ancient, low-relief volcanic mountain on the planet Mars, located in the southern hemisphere just northeast of the impact basin Hellas and southwest of the similar volcano Tyrrhenus Mons. Hadriacus Mons is in the Hellas quadrangle. It has a diameter of . The name was approved in 2007. The flanks of Hadriacus Mons have been eroded into gullies; its southern slopes are incised by the outflow
Tectonics of Mars in elevation than the southern highlands, and have a much lower crater density, indicating a younger surface age. The underlying crust is however thought to be the same age as that of the southern highlands. Unlike the southern highlands, magnetic anomalies in the northern plains are sparse and weak. The Tharsis plateau, which sits in the highland-lowland boundary, is an elevated region that covers roughly one quarter of the planet. Tharsis is topped by the largest shield volcanoes known in the solar system. Olympus Mons stands 24 km tall and is nearly 600 km in diameter. The adjoining Tharsis Montes