Olympus Mons Mons aureole deposits (discussed below). Olympus Mons lies at the edge of the Tharsis bulge, an ancient vast volcanic plateau likely formed by the end of the Noachian Period. During the Hesperian, when Olympus Mons began to form, the volcano was located on a shallow slope that descended from the high in Tharsis into the northern lowland basins. Over time, these basins received large volumes of sediment eroded from Tharsis and the southern highlands. The sediments likely contained abundant Noachian-aged phyllosilicates (clays) formed during an early period on Mars when surface water was abundant, and were thickest in the northwest
Maat Mons Maat Mons Maat Mons is a massive shield volcano. It is the second-highest mountain, and the highest volcano, on the planet Venus. It rises above the mean planetary radius at , and nearly 5 km above the surrounding plains. It is named after the Egyptian goddess of truth and justice, Ma'at. Maat Mons has a large summit caldera, 28×31 km in size. Within the large caldera there are at least five smaller collapse craters, up to 10 km in diameter. A chain of small craters 3–5 km in diameter extends some 40 km along the southeast flank of the volcano,