Irnini Mons is a volcanic structure on the planet Venus, is named after the Assyro-Babylonian goddess of cedar-tree mountains. It has a diameter of 475 km, a height of 1.75 km, is located in Venus' northern hemisphere. More it is located in the central Eistla Regio region at in the V-20 quadrangle. Sappho Patera, a 225 km 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. 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, the Virtus Linea rift continuing to the southeast. The combination of volcanic-tectonic structures around Irnini Mons supports varying intensities of deformation and a multi-directional stress history. Although classified as a shield volcano, Irnini Mons contains many elements of the Venusian coronae, bringing speculation to its formation.
If Irnini Mons was a corona, a shallow oval-shaped depression, it would support a thin lithosphere on Venus. On the other hand, it being a shield volcano supports the theory of a thicker lithosphere and Irnini Mons' stress history could be summarized as a transition from predominantly compressive forces to extensional relaxation, resulting in the observed radiating graben and concentric ridges. Irnini Mons is a significant structural feature on Venus because the preservation of the geology allows for the analysis of Venus' regional stress orientation in response to a pressurized magma chamber over time; the geology of Irnini Mons and the surrounding region was interpreted using synthetic aperture radar data from the Magellan space mission. Stratigraphic units were identified using their relative brightness and texture. Topography and structural features, such as cross-cutting relationships, were taken into account; the low erosional rates on Venus contribute to the preservation of many of these volcanic-tectonic features.
The high pressure inhibits wind erosion, the dryness prevents water erosion, the lack of volatiles in magma results in structures that are untouched. Irnini Mons is composed of continuous flows of basaltic lava, with younger pyroclastic material within the flows near the summit; the younger flows resurface and superimpose the older flows as seen by the intensity of observable wrinkle ridge deformation decreasing from older to younger flows. Irini Mons is characterized by various fracture and graben complexes; this includes north-south trending rift and ridge structures that are parallel to the Badb Linea rift zone. Furthermore, many graben radiate from the central magma chamber resulting in a symmetrical web of structures; the radial graben are reflective in radar imaging and, therefore noticeable. This radial network is a result of regional stresses that are altered closer to the magma-pressurized summit of Irnini Mons; the pressure from the magma chamber results in radiating graben because the regional linear compression is altered to radial compression in proximity to its "pressurized hole".
Circumferential ridges and graben are highly reflective to radar, therefore observed around the Sappho Patera depression. These concentric features formed after Irnini Mons lost the high pressure dynamic support from the mantle upwelling due to the lack of overlying flows; the presence of circumferential structures along a shallow depression on Irnini Mons' summit is a characteristic of coronae on Venus. The presence of corona-like features suggest two possible theories for interpretation of how Irnini Mons developed. One hypothesis is a transition from a shield volcano structure to a corona structure due to continued lithosphere thinning and lack of resurfacing flows. Another hypothesis is Irnini Mons was a corona, uplifted due to compressive forces; the low viscosity basaltic flows that compose Irnini Mons overlay several regional plains and tessera units of Eistla Regio. The oldest observed rocks are a deformed tessera unit with ridges and grabens at high angles between one another which create the tessera-textured pattern for which it is named.
The plains units are less deformed, but show a dominant linear trend of wrinkle ridges going in an east-west direction from the prevalent north-south compression. The tessera structures are truncated by the east-west wrinkle ridges, indicating the tessera formed before the wrinkle ridges; the youngest plains material is less deformed than the older plains material and underlies the Irnini flows. All impact craters observed occurred prior to formation of the east-west wrinkle ridges; the largest regional structure is the Guor Linea rift extending to the northwest, with its counterpart, the Virtus Linea rift, trending back in a southeast direction. Both of these rift zones cut through the plains units but not through Irnini Mons, indicating the Irnini flows postdate these rifts. Badb Linea is the third rift zone and consists of spaced, linear grabens trending in a north-south direction. However, unlike the other rifts, Badb Linea has structures which both truncate and cross-cut the Irnini flows, signifying that its rifting occurred before and after the Irnini flows.
The abundance of tectonic structures in proximity to Irnini Mons provides indications for the regional stress orientation of the shallow crust, as well as local timelines. The dominant change from east-west trending regional wrinkle ridges to radial ridges around
Ozza Mons is a inactive volcano on planet Venus near the equator. Four temporally variable surface hotspots were discovered at the Ganiki Chasma rift zone near volcanoes Ozza Mons and Maat Mons in 2015, suggestive of present volcanic activity. However, interpreting these types of observations from above the cloud layer is a challenge. Geology of Venus Volcanology of Venus
Sachs Patera is a feature on Venus. Defined as a sag-caldera, Sachs is an elliptical depression 130 meters in depth, spanning 40 kilometers in width along its longest axis; the morphology implies that a chamber of molten material drained and collapsed, forming a depression surrounded by concentric scarps spaced 2 to 5 kilometres apart. The arc-shaped set of scarps, extending out to the north from the prominent ellipse, is evidence for a separate episode of withdrawal. Solidified lava flows 10 to 25 kilometres long give the caldera its flower-like appearance; the flows are a lighter tone of gray in the radar data because the lava is blockier in texture and returns more radar waves. Much of the lava, evacuated from the chamber traveled to other locations underground, while some of it may have surfaced further south; this is unlike calderas on Earth, where a rim of lava builds up in the immediate vicinity of the caldera. "Venus—Sag Caldera'Sachs Patera". NASA/JPL. Retrieved 24 November 2010
Akna Montes are a mountain range on Venus centered at 68.9°N, 318.2°E and stretching 830 km long. The Akna range is a north-south trending ridge belt that forms the western border of the elevated smooth plateau of Lakshmi Planum; the Lakshmi plateau plains are formed by extensive volcanic eruptions and are bounded by mountain chains on all sides. The plains appear to be deformed near the mountains; this suggests that some of the mountain building activity occurred after the plains formed
Artemis Corona is a corona found in the Aphrodite Terra continent, on the planet Venus, at 35°S 135°E. Named after Artemis, the virgin goddess of hunting, it is the largest corona on Venus, with a diameter of 2,600 kilometers, it is enclosed by the near circular Artemis Chasma - a circular belt of arc-shaped features believed to be of compressional origin. Artemis is an unusual feature on Venus as it has been interpreted to be the site of plate tectonics operating on a regional scale. There are compressional arcs which rise above the surrounding plains; as a whole, Artemis is not elevated like other coronae. Regions within Artemis are in fact some 4 km below the surrounding plains; the differences between the highest and the lowest point within Artemis are in the order of 7.5 km. The central rift region of Artemis has been interpreted as a spreading zone, offset - with clear signs of strike-slip faulting offsetting the central rift zone. Retrograde subduction is interpreted to occur at the circular arc belts of Artemis Chasmata.
A picture of Artemis Corona and its Chasma from NASA A 3-dimensional profile of Artemis region See: http://www.windows.ucar.edu/tour/link=/venus/interior/V_coronae.html&fr=t
Abeona Mons is a mountain on Venus named after the goddess Abeona
Sif Mons is a shield volcano in Eistla Regio on Venus. It has a height of 2.0 kilometers. It is named after the Norse goddess Sif