Lunar dome
Encyclopedia
Shield volcano
A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes...
that is found on the surface of the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
's Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
. They are typically formed by highly viscous, possibly silica-rich lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
, erupting from localized vents followed by relatively slow cooling. Lunar domes are wide, rounded, circular features with a gentle slope rising in elevation a few hundred meters to the mid-point. They are typically 8-12 km in diameter, but can be up to 20 km across. Some of the domes contain a small craterlet at the peak.
Some of the domes have been shown to consist of the same materials as the lunar maria. Thus they could be created by some mechanism that differs from the mare-forming flows. It is thought that these domes are formed from a smaller magma chamber
Magma chamber
A magma chamber is a large underground pool of molten rock found beneath the surface of the Earth. The molten rock in such a chamber is under great pressure, and given enough time, that pressure can gradually fracture the rock around it creating outlets for the magma...
that is closer to the surface than is the case for a mare. This results in a lower pressure, and so the lava flows more slowly. The magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
wells up through a crack in the surface, but the flow eventually concentrates through one primary vent. This concentration can then result in a vent crater at the peak of the dome.
There are concentrations of lunar domes near the craters Hortensius
Hortensius (crater)
Hortensius is a small, bowl-shaped lunar impact crater that is located in the northern part of the Mare Insularum. It lies some distance to the west-southwest of the prominent crater Copernicus. Hortensius is circular and cup-shaped, with a small floor at the mid-point of the sloping interior walls...
, Marius
Marius (crater)
Marius is a lunar crater located on the Oceanus Procellarum. The surface to the west and north of this crater contains a large number of lunar domes spread across an area over a hundred kilometers in diameter that may be of volcanic origin dubbed the Marius Hills...
and T. Mayer
T. Mayer (crater)
T. Mayer, or Tobias Mayer, is a lunar crater that is located at the western end of the Montes Carpatus mountain range along the southern edge of Mare Imbrium. To the west is the Oceanus Procellarum, and to the south is Mare Insularum...
, and across the top of Mons Rümker
Mons Rümker
Mons Rümker is an isolated volcanic formation that is located in the northwest part of the Moon's near side, at selenographic coordinates 40.8° N, 58.1° W. The feature forms a large, elevated mound in the northern part of the Oceanus Procellarum. The mound has a diameter of 70 kilometres, and...
. Solitary lunar domes are also found on the near side, including Kies Pi
Kies (crater)
Kies is the remnant of a lunar crater that has been flooded by basaltic lava, leaving only a remnant of the outer rim. It is located in the Mare Nubium almost due south of the crater Bullialdus. Northwest of Kies is König. To the south-southwest lies a lunar dome structure designated Kies Pi...
(π), Milichius Pi
Milichius (crater)
Milichius is a bowl-shaped lunar impact crater that is located in the northern part of the Mare Insularum. To the southeast is the slightly larger Hortensius, a similar formation. Further away due east of Milichius is the prominent and well-known Copernicus....
(π), Mons Gruithuisen Gamma
Mons Gruithuisen Gamma
Mons Gruithuisen Gamma is a lunar dome that lies to the north of the crater Gruithuisen at the western edge of the Mare Imbrium. It is located at selenographic coordinates 36.6° N, 40.5° W. It is named after the King of Zanzibar's favourite cat....
(γ) and Delta (δ), and a dome near the craters Gambart C
Gambart (crater)
Gambart is a small lunar crater on the Mare Insularum, near the central region of the Moon. It can be located to the south-southeast of the prominent ray crater Copernicus. In the past, the floor of Gambart has been flooded with lava, leaving a relatively flat surface surrounded by a smooth but...
, Beer
Beer (lunar crater)
Beer is a relatively small lunar impact crater located on the Mare Imbrium, to the east of the crater Timocharis. Just to the northwest is the matching twin Feuillée....
and Capuanus
Capuanus (crater)
Capuanus is a lunar crater that lies along the southern edge of the Palus Epidemiarum. The outer rim is eroded and indented by lesser crater impacts, with notches in the north, west, and southern parts of the rim. The interior floor has been resurfaced by basaltic lava, which is connected to the...
. Omega Cauchy (ω) and Tau Cauchy (τ) form a pair of domes near the crater Cauchy
Cauchy (crater)
Cauchy is a small lunar impact crater on the eastern Mare Tranquillitatis. It is circular and symmetric, with a small interior floor at the mid-point of the sloping inner walls. Due to the high albedo of this bowl-shaped formation, it is particularly prominent at full Moon...
. Likewise near Arago
Arago (lunar crater)
Arago is a lunar impact crater located in the western part of the Mare Tranquillitatis. To the southwest lies the crater Manners, and beyond are Dionysius and the Ritter–Sabine crater pair. To the southeast is the large Lamont formation that has been submerged by the mare.The rim of Arago has a...
are the domes Arago Alpha (α) and Arago Beta (β).