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), and is about two and a half times Mount Everest's height above sea level. It is one of Mars's largest volcanoes, its tallest planetary mountain, and is approximately tied with Rheasilvia as the tallest mountain currently discovered in the Solar System. It is associated with the Tharsis Montes, a large volcanic region on Mars. It last erupted 25 million years ago.
Ascraeus Mons is a large shield volcano located in the Tharsis region of the planet Mars. It is the northernmost and tallest of three shield volcanoes collectively known as the Tharsis Montes.
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.
The geology of Venus is the scientific study of the surface, crust, and interior of the planet Venus. Of all the other planets in the Solar System, it is the one nearest to Earth and most like it in terms of mass, but has no magnetic field or recognizable plate tectonic system. Much of the ground surface is exposed volcanic bedrock, some with thin and patchy layers of soil covering, in marked contrast with Earth, the Moon, and Mars. Some impact craters are present, but Venus is similar to Earth in that there are fewer craters than on the other rocky planets that are largely covered by them. This is due in part to the thickness of the Venusian atmosphere disrupting small impactors before they strike the ground, but the paucity of large craters may be due to volcanic re-surfacing, possibly of a catastrophic nature. Volcanism appears to be the dominant agent of geological change on Venus. Some of the volcanic landforms appear to be unique to the planet. There are shield and composite volcanoes similar to those found on Earth. Given that Venus has approximately the same size, density, and composition as Earth, it is plausible that volcanism may be continuing on the planet today, as demonstrated by recent studies.
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 density that is 90 times that of Earth's atmosphere.
The Tolstoj quadrangle in the equatorial region of Mercury runs from 144 to 216° longitude and -25 to 25° latitude. It was provisionally called "Tir", but renamed after Leo Tolstoy by the International Astronomical Union in 1976. Also called Phaethontias.
The Michelangelo quadrangle is in the southern hemisphere of the planet Mercury, where the imaged part is heavily cratered terrain that has been strongly influenced by the presence of multiring basins. At least four such basins, now nearly obliterated, have largely controlled the distribution of plains materials and structural trends in the map area. Many craters, interpreted to be of impact origin, display a spectrum of modification styles and degradation states. The interaction between basins, craters, and plains in this quadrangle provides important clues to geologic processes that have formed the morphology of the mercurian surface.
Ovda Regio is a Venusian crustal plateau located near the equator in the western highland region of Aphrodite Terra that stretches from 10°N to 15°S and 50°E to 110°E. Known as the largest crustal plateau in Venus, the regio covers an area of approximately 15,000,000 square kilometres (5,800,000 sq mi) and is bounded by regional plains to the north, Salus Tessera to the west, Thetis Regio to the east, and Kuanja as well as Ix Chel chasmata to the south. The crustal plateau serves as a place to hold the localized tessera terrains in the planet, which makes up roughly 8% of Venus' surface area. The kinematic evolution of crustal plateaus on Venus has been a debated topic in the planetary science community. Understanding its complex evolution is expected to contribute to a better knowledge of the geodynamic history of Venus. It is named after a Marijian forest spirit that can appear as both male and female.
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 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 Earth and Mars 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 and minerals.
The Phlegra Montes are a system of eroded Hesperian–Noachian-aged massifs and knobby terrain in the mid-latitudes of the northern lowlands of Mars, extending northwards from the Elysium Rise towards Vastitas Borealis for nearly 1,400 km (870 mi). The mountain ranges separate the large plains provinces of Utopia Planitia (west) and Amazonis Planitia (east), and were named in the 1970s after a classical albedo feature. The massif terrains are flanked by numerous parallel wrinkle ridges known as the Phlegra Dorsa.
Lineated valley fill (LVF), also called lineated floor deposit, is a feature of the floors of some channels on Mars, exhibiting ridges and grooves that seem to flow around obstacles. Shadow measurements show that at least some of the ridges are several metres high. LVF is believed to be ice-rich. Hundreds of metres of ice probably lie protected in LVF under a thin layer of debris. The debris consists of wind-borne dust, material from alcove walls, and lag material remaining after ice sublimated from a rock-ice mixture. Some glaciers on Earth show similar ridges. High-resolution pictures taken with HiRISE reveal that some of the surfaces of lineated valley fill are covered with strange patterns called closed-cell and open-cell brain terrain. The terrain resembles a human brain. It is believed to be caused by cracks in the surface accumulating dust and other debris, together with ice sublimating from some of the surfaces. The cracks are the result stress from gravity and seasonal heating and cooling. This same type of surface is present on Lobate debris aprons and Concentric crater fill so all three are believed to be related.
Glaciers, loosely defined as patches of currently or recently flowing ice, are thought to be present across large but restricted areas of the modern Martian surface, and are inferred to have been more widely distributed at times in the past. Lobate convex features on the surface known as viscous flow features and lobate debris aprons, which show the characteristics of non-Newtonian flow, are now almost unanimously regarded as true glaciers.
NASA's Magellan spacecraft mission discovered that Venus has a geologically young surface with a relatively uniform age of 500±200 Ma. The age of Venus was revealed by the observation of over 900 impact craters on the surface of the planet. These impact craters are nearly uniformly distributed over the surface of Venus and less than 10% have been modified by plains of volcanism or deformation. These observations indicate that a catastrophic resurfacing event took place on Venus around 500 Ma, and was followed by a dramatic decline in resurfacing rate. The radar images from the Magellan missions revealed that the terrestrial style of plate tectonics is not active on Venus and the surface appears to be immobile at the present time. Despite these surface observations, there are numerous surface features that indicate an actively convecting interior. The Soviet Venera landings revealed that the surface of Venus is essentially basaltic in composition based on geochemical measurements and morphology of volcanic flows. The surface of Venus is dominated by patterns of basaltic volcanism, and by compressional and extensional tectonic deformation, such as the highly deformed tesserae terrain and the pancake like volcano-tectonic features known as coronae. The planet's surface can be broadly characterized by its low lying plains, which cover about 80% of the surface, 'continental' plateaus and volcanic swells. There is also an abundance of small and large shield volcanoes distributed over the planet's surface. Based on its surface features, it appears that Venus is tectonically and convectively alive but has a lithosphere that is static.
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.
Devana Chasma is a weak extensional rift zone on Venus, with a length of 4000 km, a width of 150–250 km, and a depth reaching 5 km. Most of the faults are facing north–south. The rift is located in Beta Regio, a 3000 km rise created by volcanic activity. Mantle plumes rising from the bottom are the reason behind the formation of the rift zone. The slow extension rates in the rift may be driven by the same reason.
Lada Terra 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.
The mapping of Venus refers to the process and results of human description of the geological features of the planet Venus. It involves surface radar images of Venus, construction of geological maps, and the identification of stratigraphic units, volumes of rock with a similar age.
