Olympus Mons is a large shield volcano on Mars. It is over 21.9 km high as measured by the Mars Orbiter Laser Altimeter (MOLA), about 2.5 times the elevation of Mount Everest above sea level. It is Mars's tallest volcano, its tallest planetary mountain, and is approximately tied with Rheasilvia on Vesta as the tallest mountain currently discovered in the Solar System. It is associated with the volcanic region of Tharsis Montes. It last erupted 25 million years ago.
Volcanism, vulcanism, volcanicity, or volcanic activity is the phenomenon where solids, liquids, gases, and their mixtures erupt to the surface of a solid-surface astronomical body such as a planet or a moon. It is caused by the presence of a heat source, usually internally generated, inside the body; the heat is generated by various processes, such as radioactive decay or tidal heating. This heat partially melts solid material in the body or turns material into gas. The mobilized material rises through the body's interior and may break through the solid surface.
A shield volcano is a type of volcano named for its low profile, resembling a shield lying on the ground. It is formed by the eruption of highly fluid lava, which travels farther and forms thinner flows than the more viscous lava erupted from a stratovolcano. Repeated eruptions result in the steady accumulation of broad sheets of lava, building up the shield volcano's distinctive form.
Tharsis is a vast volcanic plateau centered near the equator in the western hemisphere of Mars. The region is home to the largest volcanoes in the Solar System, including the three enormous shield volcanoes Arsia Mons, Pavonis Mons, and Ascraeus Mons, which are collectively known as the Tharsis Montes. The tallest volcano on the planet, Olympus Mons, is often associated with the Tharsis region but is actually located off the western edge of the plateau. The name Tharsis is the Greco-Latin transliteration of the biblical Tarshish, the land at the western extremity of the known world.
Alba Mons is a volcano located in the northern Tharsis region of the planet Mars. It is the biggest volcano on Mars in terms of surface area, with volcanic flow fields that extend for at least 1,350 km (840 mi) from its summit. Although the volcano has a span comparable to that of the United States, it reaches an elevation of only 6.8 km (22,000 ft) at its highest point. This is about one-third the height of Olympus Mons, the tallest volcano on the planet. The flanks of Alba Mons have very gentle slopes. The average slope along the volcano's northern flank is 0.5°, which is over five times lower than the slopes on the other large Tharsis volcanoes. In broad profile, Alba Mons resembles a vast but barely raised welt on the planet's surface. It is a unique volcanic structure with no counterpart on Earth or elsewhere on Mars.
Maat Mons is a massive shield volcano on the planet Venus and the planet's second-highest mountain and highest volcano. It rises 8 kilometres (5.0 mi) above the mean planetary radius at 0.5°N 194.6°E, and nearly 5 km above the surrounding plains. It is named after the Egyptian goddess of truth and justice, Ma'at.
Sapas Mons is a large volcano located in the Atla Regio region of Venus.
Theia Mons is a large highland shield volcano on the planet Venus. Located near the center of Beta Regio, a large region of recent volcanic uplift due to a currently active mantle plume, Theia Mons is situated at the junction of three branches of Devana Chasma, an extensive rift system. It is named after Theia, a Titan from Greek mythology; the name Theia Mons was officially approved by the International Astronomical Union (IAU) in 1979.
The surface of Venus is dominated by volcanic features and has more volcanoes than any other planet in the Solar System. It has a surface that is 90% basalt, and about 65% of the planet consists of a mosaic of volcanic lava plains, indicating that volcanism played a major role in shaping its surface. There are more than 1,000 volcanic structures and possible periodic resurfacing of Venus by floods of lava. The planet may have had a major global resurfacing event about 500 million years ago, from what scientists can tell from the density of impact craters on the surface. Venus has an atmosphere rich in carbon dioxide, with a pressure that is 90 times that of Earth's atmosphere.
Gula Mons is a volcano in western Eistla Regio on Venus; it is 3 kilometers (1.9 mi) high and located at approximately 22 degrees north latitude, 359 degrees east longitude.
Sif Mons is an active shield volcano located in Eistla Regio on Venus. It has a diameter of 500 kilometers (310 mi) and a height of 2.2 kilometers (1.4 mi). The volcano is one of the few identified active extraterrestrial volcanoes, having last erupted between 1990 and 1992. It is named after the Norse goddess Sif; the name Sif Mons was officially adopted by the International Astronomical Union (IAU) in 1982.
Volcanic activity, or volcanism, has played a significant role in the geologic evolution of Mars. Scientists have known since the Mariner 9 mission in 1972 that volcanic features cover large portions of the Martian surface. These features include extensive lava flows, vast lava plains, and, such as Olympus Mons, the largest known volcanoes in the Solar System. Martian volcanic features range in age from Noachian to late Amazonian, indicating that the planet has been volcanically active throughout its history, and some speculate it probably still is so today. Both Mars and Earth are large, differentiated planets built from similar chondritic materials. Many of the same magmatic processes that occur on Earth also occurred on Mars, and both planets are similar enough compositionally that the same names can be applied to their igneous rocks.
Tyrrhenus Mons, formerly Tyrrhena Mons or Tyrrhena Patera, is a large volcano in the Mare Tyrrhenum quadrangle of Mars, located at 21.36° south latitude and 253.47° west longitude. The name "Tyrrhena Patera" now refers only to the central depression, a volcanic crater or caldera. It was named after a classical albedo feature name. Pit chains are found at the summit of Tyrrhenus Mons. They are formed by collapse of material into underground voids. Since they form chains and concentric fractures that are aligned, they are probably caused by extension of the surface. Volcanic processes made the crust pull apart. Voids were formed, then material fell into them, leaving holes. It is one of the oldest volcanoes on Mars. As a consequence of its old age, Tyrrhenus Mons has many radiating gullies on its slope. When it was formed, magma may have gone through frozen ground and then erupted as easily eroded ash, instead of lava flows.
Guinevere Planitia is an expansive lowland region of Venus that lies east of Beta Regio and west of Eistla Regio. These low-lying plains, particularly in the western portion, are characterized by apparent volcanic source vents and broad regions of bright, dark, and mottled deposits. They are the only break in an equatorially connected zone of highlands and tectonic zones. The types, numbers, and patterns of mapped tectonic features and small volcanic landforms in the region provide important detail in the interpretation and evolution of venusian landscape.
Irnini Mons is a volcanic structure on the planet Venus, and is named after the Assyro-Babylonian goddess of cedar-tree mountains. It has a diameter of 475 km (295 mi), a height of 1.75 km (1.09 mi), and is located in Venus' northern hemisphere. More specifically, it is located in the central Eistla Regio region at in the V-20 quadrangle. Sappho Patera, a 225 km (140 mi) diameter wide, caldera-like, depression tops the summit of Irnini Mons. The primary structural features surrounding Irnini Mons are graben, seen as linear depressed sections of rock, radiating from the central magma chamber. Also, concentric, circular ridges and graben outline the Sappho Patera depression at the summit. The volcano is crossed by various rift zones, including the north-south trending Badb Linea rift, the Guor Linea rift extending to the northwest, and the Virtus Linea rift continuing to the southeast.
Lada Terra, named for a Slavic goddess of Love, is a major landmass near the south pole of Venus which is centered at 60°S and 20°E and has a diameter of 8,615 kilometres (5,353 mi). It is defined by the International Astronomical Union as one of the three "major landmasses," or terrae, of Venus. The term "landmass" is not analogous to the landmass on Earth, as there are no apparent oceans on Venus. The term here applies to a substantial portion of land that lies above the average planetary radius, and corresponds to highlands.
Ganis Chasma is a group of rift zones on the surface of the planet Venus. Bright spots detected by the Venus Monitoring Camera on the European Space Agency's Venus Express in the area suggest that there may be active volcanism on Venus.
The surface of Venus is dominated by geologic features that include volcanoes, large impact craters, and aeolian erosion and sedimentation landforms. Venus has a topography reflecting its single, strong crustal plate, with a unimodal elevation distribution that preserves geologic structures for long periods of time. Studies of the Venusian surface are based on imaging, radar, and altimetry data collected from several exploratory space probes, particularly Magellan, since 1961. Despite its similarities to Earth in size, mass, density, and possibly composition, Venus has a unique geology that is unlike Earth's. Although much older than Earth's, the surface of Venus is relatively young compared to other terrestrial planets, possibly due to a global-scale resurfacing event that buried much of the previous rock record. Venus is believed to have approximately the same bulk elemental composition as Earth, due to the physical similarities, but the exact composition is unknown. The surface conditions on Venus are more extreme than on Earth, with temperatures ranging from 453 to 473 °C and pressures of 95 bar. Venus lacks water, which makes crustal rock stronger and helps preserve surface features. The features observed provide evidence for the geological processes at work. Twenty feature types have been categorized thus far. These classes include local features, such as craters, coronae, and undae, as well as regional-scale features, such as planitiae, plana, and tesserae.
Idunn Mons is a shield volcano on the planet Venus. It is named after Iðunn, a goddess in Norse mythology.
