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crater and floor
At the Alphonsus, three scientific objectives were determined to be of primary interest and paramount importance: the possibility of old, pre-Imbrium impact material from within the crater's wall, the composition of the crater's interior and the possibility of past volcanic activity on the floor of the crater at several smaller " dark halo " craters.
In simple craters, the original excavation cavity is overlain by a lens of collapse breccia, ejecta and melt rock, and a portion of the central crater floor may sometimes be flat.
* A layer of shattered or " brecciated " rock under the floor of the crater.
A geological structure exists in the sea floor off the west coast of India that has been suggested as a possible impact crater, in this context called the Shiva crater.
The surface of the glacier, once mostly without crevasses, turned into a chaotic jumble of icefalls heavily criss-crossed with crevasses and seracs caused by movement of the crater floor.
Breccia of this type may be present on or beneath the floor of the crater, in the rim, or in the ejecta expelled beyond the crater.
This led Barringer to believe that the bulk of the impactor could still be found under the crater floor.
The streaks on the right are sand dunes on the crater floor.
The large crater with the dark floor ( right of center ) is Hamlet ( crater ) | Hamlet ; the crater Othello is to its lower left, and Mommur Chasma is at upper left.
The mare material is thought to be about 5 km deep, giving the Imbrium Basin a total depth of 12 km ; it is thought that the original crater left by the Imbrium impact was as much as 100 km deep, but that the floor of the basin bounced back upwards immediately afterwards.
The main crater floor lies at about 1, 100 m.
Its surface lies about 50 m below the level of the main crater floor and covers about 12 km².
The crater has a central dome on its floor a few kilometers high.
It starts at the edge of Oceanus Procellarum near the modest crater Sirsalis from which it gets its name and proceeds directly away from the mare, eventually ending up among the cracks in the floor of the crater Darwin.
The walled plain Bel ' kovich spills over the northwestern portion of Mare Humboldtianum, and the flooded crater Bel ' kovich A lies across the southwestern rim of Bel ' kovich and part of the floor of the mare.
Herschel's diameter is almost a third of the moon's own diameter ; its walls are approximately high, parts of its floor measure deep, and its central peak rises above the crater floor.
* In 1992, Audouin Dollfus of the Observatoire de Paris reported anomalous features on the floor of Langrenus crater using a one-meter ( 3. 2-foot ) telescope.
The fractured floor of this crater was cited as a possible source of the gas.
Beginning in October 1902, a dramatic volcanic spine grew from the crater floor in the Étang Sec crater, reaching a maximum width of about and a height of about.

crater and is
* The crater Anaximenes on the Moon is named in his honour.
* Balboa ( lunar crater ), a lunar crater that is located near the western limb of the Moon
The higher altitudes of the islands are accessible on the islands of Fogo, where there is a road to the volcano and walks up to the crater, and the mountainous Santo Antão where there are hiking routes.
However, the top of the system is sharply defined, being placed at an iridium-rich layer found worldwide that is believed to be associated with the Chicxulub impact crater in Yucatan and the Gulf of Mexico.
In addition to the Chicxulub Crater, there is the Boltysh crater in Ukraine, the Silverpit crater, a suspected impact crater in the North Sea, and the controversial and much larger Shiva crater.
Meteor Crater is perhaps the best-known example of a small impact crater on the Earth.
Since that time, the rate of crater production on Earth has been considerably lower, but it is appreciable nonetheless ; Earth experiences from one to three impacts large enough to produce a 20 km diameter crater about once every million years on average.
Daniel Barringer ( 1860 – 1929 ) was one of the first to identify an impact crater, Meteor Crater in Arizona ; to crater specialists the site is referred to as Barringer Crater in his honor.
In practice, there is overlap between the three processes with, for example, the excavation of the crater continuing in some regions while modification and collapse is already underway in others.
The subsequent excavation of the crater occurs more slowly, and during this stage the flow of material is largely sub-sonic.
Ejecta thrown out of the crater do not include material excavated from the full depth of the transient cavity ; typically the depth of maximum excavation is only about a third of the total depth.
As a result, about one third of the volume of the transient crater is formed by the ejection of material, and the remaining two thirds is formed by the displacement of material downwards, outwards and upwards, to form the elevated rim.
Most material ejected from the crater is deposited within a few crater radii, but a small fraction may travel large distances at high velocity, and in large impacts it may exceed escape velocity and leave the impacted planet or moon entirely.
As ejecta escapes from the growing crater, it forms an expanding curtain in the shape of an inverted cone ; the trajectory of individual particles within the curtain is thought to be largely ballistic.
In small craters, less than about 4 km diameter on Earth, there is some limited collapse of the crater rim coupled with debris sliding down the crater walls and drainage of impact melts into the deeper cavity.

crater and otherwise
The crater is otherwise free of significant impacts within the rim.
The crater must be younger than the Early Cretaceous age of the rocks in which it is situated, but otherwise is not well dated.
This crater is best observed under oblique illumination, as it is otherwise difficult to find.
The crater is otherwise undistinguished.
Together the crater Hyginus and Rima Hyginus form a distinctive and prominent feature in an otherwise flat surface.
The crater is otherwise unremarkable.
It lies across the southeast rim of the larger crater Stöfler, and the northwest rim of Faraday forms a wide rampart across the otherwise flat floor of Stöfler.
The crater is otherwise not particularly eroded by impacts.
The satellite crater Anuchin L lies astride the southern rim, but the otherwise the outer wall is not significantly incised.
Brianchon A forms an outward bulge in the rim to the northwest, but otherwise merges seamlessly into the crater formation.
The rim of this crater has a noticeable outward bulge toward the south, but it is otherwise relatively circular.
There is a small crater across the northwest rim, but otherwise the formation is not significantly marked by impacts.
There is an area of rough terrain just to the east of this crater, but the surroundings are otherwise level with only a few small craters in the vicinity.
A smaller crater is located just to the west-southwest of this centrally-located formation, but the flat interior floor is otherwise devoid of features of interest.
A small craterlet lies along the northwestern inner wall of the crater, but the formation is not otherwise significantly marked by smaller impacts.
There is a tiny craterlet along the northern rim, but otherwise the crater contains no impacts of note.
It lies to the northeast of the crater Harding, but is otherwise relatively isolated.
The small satellite crater Macrobius C lies across the western rim, but the wall is otherwise relatively free of significant wear.
The crater floor is marked by a number of tiny craterlets but otherwise relatively featureless, having no central peak.
It lies about two crater diameters to the northwest of Euler, in an otherwise isolated stretch of the mare.
It is otherwise an undistinguished crater formation.
The interior of the crater is otherwise undistinguished, being marked only by tiny craters and some low ridges along the ramparts of McNair.
Opinions after the creation of the lake that the presence of the water in the crater has a tendency to cool off the material below and thus lessen the chances of an explosion or make the volcano extinct, but the preponderance of expert opinion was otherwise.
The outer rim has a small crater joined to the eastern edge of the northern gap, but is otherwise not overlain by any notable craters.

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