38th parallel structures

<h2 id="history">History</h2>
<p>Rampino and Volk (1996) postulated that these structures could be the remains of a serial meteorite strike during the late <a href="/facts/Mississippian_age/tqsS6Ifj">Mississippian</a> or early <a href="/facts/Pennsylvanian_(geology)/Fc1LAJSX">Pennsylvanian</a> periods (320 ± 10 Ma).<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> Difficulty in determining the age of many of the structures and doubts about the exogenic origins of several of them leave some <a href="/facts/Geologist/vGc0tBHB">geologists</a> skeptical of this hypothesis. As of 2016, only two of the structures, <a href="/facts/Crooked_Creek_crater/TlEhzTNm">Crooked Creek</a> (320 ± 80 <a href="/facts/Megaannum/51V242hh">Ma</a>) and <a href="/facts/Decaturville_crater/mnoLW1d0">Decaturville</a> (< 300 Ma), both in Missouri, are listed as confirmed impact craters in the <a href="/facts/Earth_Impact_Database/EFa4bhxI">Earth Impact Database</a>.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a>
</p><p>There is evidence that at least some of the features, such as <a href="/facts/Hicks_Dome/zIu3sDLE">Hicks Dome</a> in Illinois, are volcanic in origin. These features are associated with faults and fractured rock, and are accompanied by igneous rocks and mineral deposits. Hicks Dome is a structural <a href="/facts/Dome_(geology)/EP5rbPLN">dome</a> which has its central <a href="/facts/Devonian/nWgakqzk">Devonian</a> core displaced upward some 4,000 feet (1,200 m) in relation to the surrounding <a href="/facts/Stratum/w5D4VAwa">strata</a>. The dome has small associated <a href="/facts/Igneous/xeMJhUah">igneous</a> <a href="/facts/Dike_(geology)/jf8vsEHx">dikes</a> around its flanks.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a>
</p><p>Interest in the possibility of serial impacts on Earth was piqued by observations of <a href="/facts/Comet_Shoemaker%E2%80%93Levy_9/UNFmCX83">comet Shoemaker–Levy 9</a> impacting on <a href="/facts/Jupiter/95m7XjMT">Jupiter</a> in 1994. It has been estimated, however, that the likelihood of such an event occurring on Earth is vanishingly small because the Earth's weaker gravitational field is much less able than Jupiter's to pull a speeding object close enough to be torn apart by tidal forces.  However, evidence of serial impacts on the <a href="/facts/Moon/zKHqEMPb">Moon</a>, whose gravitational field is even weaker, can be seen in several <a href="/facts/List_of_features_on_the_Moon/SX3jaH8z">chains of craters</a> on the lunar surface.
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<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Impact_event/fbWu9Q4p">Impact event</a></li>
<li><a href="/facts/Roche_limit/ho5gpNr3">Roche limit</a></li>
<li><a href="/facts/List_of_possible_impact_structures_on_Earth/y4qTejPq">List of possible impact structures on Earth</a></li></ul>

<h3>Bibliography</h3>
<ul><li>Rampino, M.R; Volk, T. (1996). <a href="https://pubs.giss.nasa.gov/docs/1996/1996_Rampino_ra05200y.pdf">"Multiple impact event in the Paleozoic: Collision with a string of comets or asteroids?"</a> (PDF). <i><a href="/facts/Geophysical_Research_Letters/xMemN0QP">Geophysical Research Letters</a></i>. 23 (1): 49–52. <a href="/facts/Bibcode_(identifier)/9HtdQSGB">Bibcode</a>:<a href="https://ui.adsabs.harvard.edu/abs/1996GeoRL..23...49R">1996GeoRL..23...49R</a>. <a href="/facts/Doi_(identifier)/muM9Etpq">doi</a>:<a href="https://doi.org/10.1029%2F95GL03605">10.1029/95GL03605</a>. Retrieved 2019-04-06.</li></ul>
<h2 id="further-reading">Further reading</h2>

<ul><li>Evans, Kevin R.; Mickus, Kevin L.; & Rovey, Charles W. III (2003). The Weaubleau Structure: Evidence of a Mississippian Meteorite Impact in Southwestern Missouri. <i>Association of Missouri Geologists Field Trip Guidebook, 50th Annual Meeting</i>. Missouri Department of Natural Resources. <a href="https://web.archive.org/web/20060429213030/http://geosciences.missouristate.edu/geology/RI-75(2003AMGguidebook).pdf">PDF</a></li>
<li>Luczaj, J. 1998. Argument supporting explosive igneous activity for the origin of "cryptoexplosion" structures in the midcontinent, United States. <i>Geology</i> 26(April):295.</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Gillman, Joe (ed.), Association of Missouri Geologists Field Trip Guidebook, 51st Annual Meeting, Rolla, Missouri, October 1–2, 2004, 2004, Missouri Department of Natural Resources, Geological Survey and Resource Assessment Division, p. 15 <a href="http://www.missourigeologists.org/Meeting2004/AMGguidebook2004.pdf" target="_blank">http://www.missourigeologists.org/Meeting2004/AMGguidebook2004.pdf</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Rampino & Volk, 1996, p.49 <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>John Spray (director) (2016-05-20). "North America". Earth Impact Database. Planetary and Space Science Centre, University of New Brunswick. Retrieved 2016-05-30. <a href="https://www.unb.ca/passc/ImpactDatabase/NorthAmerica.html" target="_blank">https://www.unb.ca/passc/ImpactDatabase/NorthAmerica.html</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Raymond Wiggers, 1997, Geology underfoot in Illinois, Mountain Press, p. 252–256. ISBN 0-87842-346-X <a href="/wiki/ISBN_(identifier)" target="_blank">/wiki/ISBN_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
</ol>

38th parallel structures open-in-new

38th parallel structures