Editing Mount Greylock (section)

==Geology==
Mount Greylock is part of the much larger Taconic [[Allochthon]],  a structure that migrated to its present position from 25 miles to the east.<ref>Potter, D. B. (December 1, 1968) "Time and space relationships of the Taconic allochthon and autochthon [book review]" [https://www.ajsonline.org/content/266/10/995]</ref> The rocks moved via [[thrust fault]]ing, a tectonic process by which older rock is thrust over and above younger rock.<ref>The Taconic Controversy: What Forces Make a Range? Appalachia: Vol. 73: No. 1 Article 5 [https://digitalcommons.dartmouth.edu/do/search/?q=author_lname%3A%22Seward%22%20author_fname%3A%22John%22&start=0&context=9951493&facet=]</ref>

More narrowly, the local massif is mostly "Greylock Schist," a term  used by geologists starting in 1891 and much more recently, although the age of these rocks had been uncertain into the 1960s.<ref>see page 41-42 of ""Taconic Stratigraphic Names: Definitions and Synonymies" by E-an Zen, 1964 U Geological Survey Bulletin 1174 [https://pubs.usgs.gov/bul/1174/report.pdf]</ref> This [[Ordovician]] schist is about 1,000 to 2,000 feet thick on Greylock and "consists of [[muscovite]] (sericite), [[chlorite]], and [[quartz]] [[schist]]." It lies above a formation called "Bellows Pipe Limestone."<ref>[https://ngmdb.usgs.gov/Geolex/UnitRefs/GreylockRefs_1897.html "National Geologic Map Database: Unit Greylock]</ref> This younger, underlying layer has been quarried on the lower  slopes of the mountain.

Successive episodes of ice-age glaciation rounded the mountain, leaving [[glacial erratics]] such as "Balanced Rock" on Greylock in Lanesborough.<ref>{{Cite web|url=http://www.stateparks.com/balance_rock_state_park_in_massachusetts.html|title=Balance Rock State Park, a Massachusetts park located near North Adams, Pittsfield and Troy|last=Walker|first=T|website=www.stateparks.com|access-date=October 20, 2017}}</ref><ref name="Raymo" /><ref name="bio">{{cite web|url=http://drm.williams.edu/nhb/|title=Natural History of the Berkshires|publisher=[[Williams College]]|access-date=March 9, 2008|archive-date=July 23, 2008|archive-url=https://web.archive.org/web/20080723214409/http://drm.williams.edu/nhb/|url-status=dead}}</ref>
The [[Laurentide Ice Sheet]] had covered the region up to a depth of one kilometer (or 3,281 feet). In melting, it formed Lake Bascom in the upper Hoosic Valley.<ref>"Lake Bascom and the deglaciation of northwestern Massachusetts" Bierman, et al., 1986 [https://www.uvm.edu/cosmolab/papers/Bierman_1986_489.pdf]</ref>
The remains of lake beaches are evident at several places on the lowest slopes of Greylock.

Geologists used [[Surface exposure dating|Surface Exposure Dating]] in 2018  to measure the rate of Pleistocene de-glaciation of the region. This method offered data in support of a more rapid melting rate in New England compared with earlier estimates.<ref name="Halsted, C.T. 2018">{{cite conference|last1=Halsted|first1=CT|last2=Shakun|first2=JD|last3=Davis|first3=PT|last4=Bierman|first4=PR|last5=Corbett|first5=LB|last6=Koester|first6=AJ|chapter=Mount Greylock as a cosmogenic nuclide dipstick to determine the timing and rate of southeastern Laurentide Ice Sheet thinning|editor1-last=Grove|editor1-first=Tim|editor2-last=Mango|editor2-first=Helen|title=Guidebook for field trips in New York and Vermont|conference=New England Intercollegiate Geological Conference, 110th Annual Meeting and New York State Geological Association, 90th Annual Meeting|date=October 12–14, 2018|location=Lake George, New York}}</ref>