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{{Short description|Large impact craters with uplifted centres}} |
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[[Image:Craterstructure.gif|thumb|right| |
[[Image:Craterstructure.gif|thumb|right|upright=1.3|Impact crater structure]] |
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[[File:Tycho LRO.png|thumb|right |
[[File:Tycho LRO.png|thumb|right|Lunar crater [[tycho (crater)|Tycho]]]] |
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| ⚫ | '''Complex craters''' are a type of large [[impact crater]] morphology. Complex craters are classified into two groups: ''central-peak craters'' and ''[[peak-ring craters]]''. Peak-ring craters have diameters that are larger in than central-peak craters and have a ring of raised [[massif]]s which are roughly half the rim-to-rim diameter, instead of a central peak.<ref name="Science Concept 6: The Moon is an Accessible Laboratory for Studying the Impact Process on Planetary Scales">{{Cite web |url=https://www.lpi.usra.edu/exploration/CLSE-landing-site-study/ScienceConcept6/ |title=Science Concept 6: The Moon is an Accessible Laboratory for Studying the Impact Process on Planetary Scales}}</ref> |
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'''Complex craters''' are a type of large [[impact crater]] morphology. |
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==Background== |
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Above a certain threshold size, which varies with planetary gravity, the collapse and modification of |
Above a certain threshold size, which varies with planetary gravity, the collapse and modification of a [[Impact crater#Excavation|transient cavity]] is much more extensive, and the resulting structure is called a ''complex crater''. The collapse of the transient cavity is driven by gravity, and involves both the uplift of the central region and the inward collapse of the rim. The central uplift is not the result of elastic rebound, which is a process in which a material with elastic strength attempts to return to its original geometry; rather the uplift is a process in which a material with little or no strength attempts to return to a state of gravitational equilibrium.<ref>{{cite book |
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| last = French |
| last = French |
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| first = Bevan M |
| first = Bevan M |
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| title = Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures |
| title = Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures |
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| |
| title-link = Traces of Catastrophe |
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| publisher = [[Lunar and Planetary Institute]] |
| publisher = [[Lunar and Planetary Institute]] |
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| date = 1998 |
| date = 1998 |
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| location = [[Houston]], [[Texas]] |
| location = [[Houston]], [[Texas]] |
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| pages = [https://archive.org/details/tracescatastroph00fren/page/n129 120] |
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| ⚫ | |||
| id = [http://www.lpi.usra.edu/publications/books/CB-954/CB-954.intro.html LPI Contribution No. 954] |
| id = [http://www.lpi.usra.edu/publications/books/CB-954/CB-954.intro.html LPI Contribution No. 954] |
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}}</ref> |
}}</ref> |
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Complex craters have uplifted centers, and they have typically broad flat shallow crater floors, and terraced walls. At the largest sizes, one or more exterior or interior rings may appear, and the structure may be labeled an ''impact basin'' rather than an impact crater. Complex-crater morphology on [[rocky planets]] appears to follow a regular sequence with increasing size: small complex craters with a central topographic peak are called ''[[central-peak craters]]'', |
Complex craters have uplifted centers, and they have typically broad flat shallow crater floors, and [[terraced walls]]. At the largest sizes, one or more exterior or interior rings may appear, and the structure may be labeled an ''impact basin'' rather than an impact crater. Complex-crater morphology on [[rocky planets]] appears to follow a regular sequence with increasing size: small complex craters with a central topographic peak are called ''[[central-peak craters]]'' (e.g., [[Tycho (crater)|Tycho]]); intermediate-sized craters, in which the central peak is replaced by a ring of peaks, are called ''[[Peak ring (crater)|peak ring]] craters'' (e.g., [[Schrodinger (crater)|Schrödinger]]); and the largest craters contain multiple concentric topographic rings, and are called ''[[multi-ringed basins]]'' (e.g., [[Mare Orientale|Orientale]]). On icy as opposed to rocky bodies, other morphological forms appear which may have central pits rather than central peaks, and at the largest sizes may contain very many concentric rings—[[Valhalla (crater)|Valhalla]] on [[Callisto (moon)|Callisto]] is the type example of the latter. |
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| ⚫ | Complex craters are classified into two groups: central-peak and [[peak-ring craters]]. Peak-ring craters have diameters that are larger in than central-peak craters and have a ring of raised [[massif]]s which are roughly half the rim-to-rim diameter, instead of a central peak.<ref name="Science Concept 6: The Moon is an Accessible Laboratory for Studying the Impact Process on Planetary Scales">{{Cite web |url=https://www.lpi.usra.edu/exploration/CLSE-landing-site-study/ScienceConcept6/ |title=Science Concept 6: The Moon is an Accessible Laboratory for Studying the Impact Process on Planetary Scales}}</ref> |
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==Central-peak craters== |
==Central-peak craters== |
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[[File:Eddie crater.jpg|thumb|right |
[[File:Eddie crater.jpg|thumb|right|[[Eddie crater]], a central peak-ring crater on [[Mars (planet)|Mars]]]] |
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A central-peak crater is the most basic form of complex crater. A central-peak crater can have a tightly spaced, ring-like arrangement of peaks, thus be a [[Peak ring (crater)|peak ring crater]], though the peak is often single.<ref name="Central Peak Crater">{{Cite book |chapter=Central Peak Crater |last=Bray |first=Veronica J. |date=November 20, 2015|doi=10.1007/978-1-4614-3134-3_37 |title=Encyclopedia of Planetary Landforms |pages=249–256 |isbn=978-1-4614-3133-6 }}</ref> Central-peak craters can occur in [[impact craters]] via [[meteorites]]. An Earthly example is [[Mistastin crater]], in [[Canada]].<ref name="Science Concept 6: The Moon is an Accessible Laboratory for Studying the Impact Process on Planetary Scales">{{Cite web |url=https://www.lpi.usra.edu/exploration/CLSE-landing-site-study/ScienceConcept6/ |title=Science Concept 6: The Moon is an Accessible Laboratory for Studying the Impact Process on Planetary Scales}}</ref> Many central-peak craters have rims that are scalloped, [[Terrace (geology)|terraced]] inner walls, and [[hummock]]y floors.<ref name="Central peak crater">{{cite book |doi=10.1007/978-1-4614-9213-9_37-2 |chapter=Central Peak Crater |title=Encyclopedia of Planetary Landforms |date=2014 |last1=Bray |first1=Veronica J. |last2=Öhman |first2=Teemu |last3=Hargitai |first3=Henrik |pages=1–9 |isbn=978-1-4614-9213-9 }}</ref> |
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A central-peak crater is the most basic form of complex crater. |
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| ⚫ | |||
A central peak crater can have a tightly spaced, ring-like arrangement of peaks, thus be a [[Peak ring (crater)|peak ring crater]], though the peak is often single.<ref name="Central Peak Crater">{{Cite web |url=https://link.springer.com/referenceworkentry/10.1007/978-1-4614-3134-3_37 |title=Central Peak Crater |last=Bray |first=Veronica J. |date=November 20, 2015}}</ref> |
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Diameters of craters where complex features form depends on the strength of gravity of the celestial body they occur on. Stronger gravity, such as on Earth compared to the Moon, causes rim collapse in smaller diameter craters. Complex craters may occur at {{convert|2|km|mi}} to {{convert|4|km|mi}} on Earth, but start from {{convert|20|km|mi}} on the Moon.<ref>{{cite book |
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| last = French |
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Central-peak craters can occur in [[impact craters]], via [[meteorites]]. An Earthly example is [[Mistastin crater]], in [[Canada]].<ref name="Science Concept 6: The Moon is an Accessible Laboratory for Studying the Impact Process on Planetary Scales">{{Cite web |url=https://www.lpi.usra.edu/exploration/CLSE-landing-site-study/ScienceConcept6/ |title=Science Concept 6: The Moon is an Accessible Laboratory for Studying the Impact Process on Planetary Scales}}</ref> They also occur due to [[volcanism]], as in [[Valles Caldera]].<ref name="Valles Caldra, Jemez Volcanic Field">{{Cite web |url=http://nmnaturalhistory.org/volcanoes/valles-caldera-jemez-volcanic-field |title=Valles Caldra, Jemez Volcanic Field}}</ref> |
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| first = Bevan M |
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| title = Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures |
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Many central-peak craters have rims that are scalloped, [[Terrace (geology)|terraced]] inner walls, and [[hummocky]] floors.<ref name="Central peak crater">{{Cite web |url=https://www.researchgate.net/publication/278689780_Central_Peak_Crater |title=Central peak crater |last=Bray |first=Veronica J |date=January 1, 2014 |website=researchgate.net}}</ref> |
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| title-link = Traces of Catastrophe |
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| publisher = [[Lunar and Planetary Institute]] |
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| ⚫ | |||
| location = [[Houston]], [[Texas]] |
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| pages = [https://archive.org/details/tracescatastroph00fren/page/n37 27] |
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| id = [http://www.lpi.usra.edu/publications/books/CB-954/CB-954.intro.html LPI Contribution No. 954] |
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}}</ref> |
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| ⚫ | |||
If [[lunar craters]] have diameters between about {{convert|20|km|mi}} to {{convert|175|km|mi}}, the central peak is usually a single peak, or small |
If [[lunar craters]] have diameters between about {{convert|20|km|mi}} to {{convert|175|km|mi}}, the central peak is usually a single peak, or small |
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group of peaks. Lunar craters of diameter greater than about {{convert|175|km|mi}} may have complex, [[Peak ring (crater)|ring-shaped uplifts]]. If impact features exceed {{convert|300|km|mi}} of diameter, they are called [[impact basins]], not craters.<ref name="Mapping The Surface of the Moon">{{Cite web |url=https://lunar.gsfc.nasa.gov/lessonkit/LROC-LOLA-Mapping%20the%20Surface%20of%20the%20Moon_2014.pdf |title=Mapping The Surface of the Moon |last=Millham |first=Rosemary}}</ref> |
group of peaks. Lunar craters of diameter greater than about {{convert|175|km|mi}} may have complex, [[Peak ring (crater)|ring-shaped uplifts]]. If impact features exceed {{convert|300|km|mi}} of diameter, they are called [[impact basins]], not craters.<ref name="Mapping The Surface of the Moon">{{Cite web |url=https://lunar.gsfc.nasa.gov/lessonkit/LROC-LOLA-Mapping%20the%20Surface%20of%20the%20Moon_2014.pdf |title=Mapping The Surface of the Moon |last=Millham |first=Rosemary}}</ref> |
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Lunar craters of {{convert|35|km|mi}} to about {{convert|170|km|mi}} in diameter possess a central peak.<ref name="Central Peak Crater"/> |
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There are several theories as to why central |
There are several theories as to why central-peak craters form. Such craters are common, on [[Earth (planet)|Earth]], the [[Moon]], [[Mars (planet)|Mars]], and [[Mercury (planet)|Mercury]].<ref name="Central peaks in lunar craters">{{Cite journal |title=Central peaks in lunar craters |journal = Moon|volume = 12|issue = 4|pages = 463–474|last=Allen |first=C. C. |date=April 12, 1975 |bibcode = 1975Moon...12..463A|doi = 10.1007/BF00577935|hdl = 10150/622036| s2cid=120245830 |hdl-access = free}}</ref><ref name="Atlas of Volcanic Landforms on Mars">{{Cite web |url=https://pubs.usgs.gov/pp/1534/report.pdf |title=Atlas of Volcanic Landforms on Mars |last=Hodges |first=Carroll Ann |date=1992 |website=pubs.usgs.gov}}</ref> |
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==Height of central peak relative to crater diameter== |
===Height of central peak relative to crater diameter=== |
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On |
On the Moon, heights of central peaks are directly proportional to diameters of craters, which implies that peak height varies with crater-forming energy.<ref name="Central Peak Crater"/> There is a similar relationship for [[terrestrial meteorite crater|terrestrial meteorite craters]] and [[trinitrotoluene|TNT]] craters whose uplifts originated from rebound.<ref name="Moon: Central peak heights and crater origins">{{cite journal |last1=Wood |first1=Charles A. |title=Moon: Central peak heights and crater origins |journal=Icarus |date=December 1973 |volume=20 |issue=4 |pages=503–506 |doi=10.1016/0019-1035(73)90023-7 |bibcode=1973Icar...20..503W }}</ref> |
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== See also == |
== See also == |
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* {{annotated link|Impact crater}} |
* {{annotated link|Impact crater}} |
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* {{annotated link|Impact structure}} |
* {{annotated link|Impact structure}} |
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* {{annotated link|Multi-ringed basin}} |
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* {{annotated link|Peak ring (crater)}} |
* {{annotated link|Peak ring (crater)}} |
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* |
* ''[[Traces of Catastrophe]]'', 1998 book from [[Lunar and Planetary Institute]] - comprehensive reference on impact crater science |
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== References == |
== References == |
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{{Portal|Astronomy}} |
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{{reflist}} |
{{reflist}} |
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{{Impact cratering on Earth}} |
{{Impact cratering on Earth}} |
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Latest revision as of 02:59, 5 September 2024
Complex craters are a type of large impact crater morphology. Complex craters are classified into two groups: central-peak craters and peak-ring craters. Peak-ring craters have diameters that are larger in than central-peak craters and have a ring of raised massifs which are roughly half the rim-to-rim diameter, instead of a central peak.[1]
Background
[edit]Above a certain threshold size, which varies with planetary gravity, the collapse and modification of a transient cavity is much more extensive, and the resulting structure is called a complex crater. The collapse of the transient cavity is driven by gravity, and involves both the uplift of the central region and the inward collapse of the rim. The central uplift is not the result of elastic rebound, which is a process in which a material with elastic strength attempts to return to its original geometry; rather the uplift is a process in which a material with little or no strength attempts to return to a state of gravitational equilibrium.[2]
Complex craters have uplifted centers, and they have typically broad flat shallow crater floors, and terraced walls. At the largest sizes, one or more exterior or interior rings may appear, and the structure may be labeled an impact basin rather than an impact crater. Complex-crater morphology on rocky planets appears to follow a regular sequence with increasing size: small complex craters with a central topographic peak are called central-peak craters (e.g., Tycho); intermediate-sized craters, in which the central peak is replaced by a ring of peaks, are called peak ring craters (e.g., Schrödinger); and the largest craters contain multiple concentric topographic rings, and are called multi-ringed basins (e.g., Orientale). On icy as opposed to rocky bodies, other morphological forms appear which may have central pits rather than central peaks, and at the largest sizes may contain very many concentric rings—Valhalla on Callisto is the type example of the latter.
Central-peak craters
[edit]
A central-peak crater is the most basic form of complex crater. A central-peak crater can have a tightly spaced, ring-like arrangement of peaks, thus be a peak ring crater, though the peak is often single.[3] Central-peak craters can occur in impact craters via meteorites. An Earthly example is Mistastin crater, in Canada.[1] Many central-peak craters have rims that are scalloped, terraced inner walls, and hummocky floors.[4]
When central peaks form
[edit]Diameters of craters where complex features form depends on the strength of gravity of the celestial body they occur on. Stronger gravity, such as on Earth compared to the Moon, causes rim collapse in smaller diameter craters. Complex craters may occur at 2 kilometres (1.2 mi) to 4 kilometres (2.5 mi) on Earth, but start from 20 kilometres (12 mi) on the Moon.[5]
If lunar craters have diameters between about 20 kilometres (12 mi) to 175 kilometres (109 mi), the central peak is usually a single peak, or small group of peaks. Lunar craters of diameter greater than about 175 kilometres (109 mi) may have complex, ring-shaped uplifts. If impact features exceed 300 kilometres (190 mi) of diameter, they are called impact basins, not craters.[6]
Lunar craters of 35 kilometres (22 mi) to about 170 kilometres (110 mi) in diameter possess a central peak.[3]
There are several theories as to why central-peak craters form. Such craters are common, on Earth, the Moon, Mars, and Mercury.[7][8]
Height of central peak relative to crater diameter
[edit]On the Moon, heights of central peaks are directly proportional to diameters of craters, which implies that peak height varies with crater-forming energy.[3] There is a similar relationship for terrestrial meteorite craters and TNT craters whose uplifts originated from rebound.[9]
See also
[edit]- Impact crater – Circular depression in a solid astronomical body formed by the impact of a smaller object
- Impact structure – Geologic structure formed from impact on a planetary surface
- Multi-ringed basin – Crater containing multiple concentric topographic rings
- Peak ring (crater) – Roughly circular ring or plateau, possibly discontinuous, surrounding an impact crater's center
- Traces of Catastrophe, 1998 book from Lunar and Planetary Institute - comprehensive reference on impact crater science
References
[edit]
- ^ a b "Science Concept 6: The Moon is an Accessible Laboratory for Studying the Impact Process on Planetary Scales".
- ^ French, Bevan M (1998). Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures. Houston, Texas: Lunar and Planetary Institute. pp. 120. LPI Contribution No. 954.
- ^ a b c Bray, Veronica J. (November 20, 2015). "Central Peak Crater". Encyclopedia of Planetary Landforms. pp. 249–256. doi:10.1007/978-1-4614-3134-3_37. ISBN 978-1-4614-3133-6.
- ^ Bray, Veronica J.; Öhman, Teemu; Hargitai, Henrik (2014). "Central Peak Crater". Encyclopedia of Planetary Landforms. pp. 1–9. doi:10.1007/978-1-4614-9213-9_37-2. ISBN 978-1-4614-9213-9.
- ^ French, Bevan M (1998). Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures. Houston, Texas: Lunar and Planetary Institute. pp. 27. LPI Contribution No. 954.
- ^ Millham, Rosemary. "Mapping The Surface of the Moon" (PDF).
- ^ Allen, C. C. (April 12, 1975). "Central peaks in lunar craters". Moon. 12 (4): 463–474. Bibcode:1975Moon...12..463A. doi:10.1007/BF00577935. hdl:10150/622036. S2CID 120245830.
- ^ Hodges, Carroll Ann (1992). "Atlas of Volcanic Landforms on Mars" (PDF). pubs.usgs.gov.
- ^ Wood, Charles A. (December 1973). "Moon: Central peak heights and crater origins". Icarus. 20 (4): 503–506. Bibcode:1973Icar...20..503W. doi:10.1016/0019-1035(73)90023-7.
