The Eratosthenian period in the
lunar geologic timescale runs from 3,200 million years ago to 1,100 million years ago. It is named after the
crater Eratosthenes, which displays characteristics typical of craters of this age, including a surface that is not significantly eroded by subsequent impacts, but which also does not possess a
ray system
In planetary geology, a ray system comprises radial streaks of fine '' ejecta'' thrown out during the formation of an impact crater, looking somewhat like many thin spokes coming from the hub of a wheel. The rays may extend for lengths up to ...
. The massive basaltic volcanism of the
Imbrian period tapered off and ceased during this long span of lunar time. The youngest lunar lava flows identified from orbital images are tentatively placed near the end of this period.
Its equivalent on Earth consists of most of the
Mesoarchean and
Neoarchean eras (
Archean
The Archean ( , also spelled Archaean or Archæan), in older sources sometimes called the Archaeozoic, is the second of the four geologic eons of Earth's history of Earth, history, preceded by the Hadean Eon and followed by the Proterozoic and t ...
eon),
Paleoproterozoic
The Paleoproterozoic Era (also spelled Palaeoproterozoic) is the first of the three sub-divisions ( eras) of the Proterozoic eon, and also the longest era of the Earth's geological history, spanning from (2.5–1.6 Ga). It is further sub ...
and
Mesoproterozoic
The Mesoproterozoic Era is a geologic era that occurred from . The Mesoproterozoic was the first era of Earth's history for which a fairly definitive geological record survives. Continents existed during the preceding era (the Paleoproterozoic ...
eras (
Proterozoic eon).
Examples
Other than Eratosthenes itself, examples of large Eratosthenian craters on the near side of the Moon include
Langrenus,
Macrobius,
Aristoteles,
Hausen,
Moretus,
Pythagoras,
Scoresby,
Bullialdus,
Plutarch
Plutarch (; , ''Ploútarchos'', ; – 120s) was a Greek Middle Platonist philosopher, historian, biographer, essayist, and priest at the Temple of Apollo (Delphi), Temple of Apollo in Delphi. He is known primarily for his ''Parallel Lives'', ...
, and
Cavalerius. On the far side, examples include
Olcott,
Hamilton,
Birkeland,
Finsen,
Kirkwood, and
Ricco.
Unified Geologic Map of the Moon
C. M. Fortezzo, P. D. Spudis, S. L. Harrel, 2020. United States Geological Survey.
File:Eratosthenes (LRO).png, Eratosthenes
File:Macrobius crater AS17-M-0296.jpg, Macrobius
File:Hausen crater 4193 h2.jpg, Hausen
File:Olcott crater AS16-M-3001 ASU.jpg, Olcott
File:Kirkwood crater 5029 h3.jpg, Kirkwood
References
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