500px|thumb|The barrier nature of the ridge and valley physiognomy gives ample hint as to how difficult passing west across the Appalachians was until railroads pierced the four water gaps to the interior west of the Hudson. Even in New England, travel through the range is dependent upon low passes and valleys through water gaps.

The terms '''barrier ridge''',<ref name=ribbon>{{cite web | website = English Dictionary online | url = https://en.glosbe.com/en/en/barrier%20ridge | publisher = English English Dictionary online | title = ''Example sentences with "barrier ridge"'' | quote = On the east side, the sand barrier ridge that separates the park's marshlands from the lake has been reduced to a slim ribbon of sand that occasionally is breached, exposing the marsh to the lake. | accessdate = 2016-05-07 }}</ref><!--

---> a term of art<ref name=Lawson>{{cite book | date = 1894<!-- | website = [https://books.google.com/books Googlebooks free e-reprints] ---> | url = https://books.google.com/books?id=3BO2AAAAIAAJ&pg=PA251&lpg=PA251&dq=<!-- --->barrier+ridge&source=bl&ots=7r_uRld9_T&sig=fBcPELey_ZR7z6kY2xJVot187ng&hl=<!-- --->en&sa=X&ved=0ahUKEwjYxaWO58rMAhVINT4KHdCZA4A4FBDoAQgoMAI#v=<!-- --->onepage&q=barrier%20ridge&f=false | page = 244, 251 | quote = On a still lower delta plain and much nearer the lake is still another low barrier ridge which has an elevation of 103.5 feet (IX). The church of the village stands on... | title = publication: Collected Papers of Andrew Cowper Lawson, Volume I (1885-1894) {{bull }} ''reprinted in'' '''''State Geologist''', Twentieth Annual Report, 1894'' | work =Paper: V. Sketch of the Coastal Topography of the North Side of LAKE SUPERIOR &mdash; With Special Reference to the Abandoned Strands of LAKE WARREN (The Greatest of the Late Quaternary Lakes of North America) | editor = ''Googlebooks reprint title''<!-- Collected papers, Volume 1; Work title:'' 'Collected papers, Andrew Cowper Lawson, Published 1894', ''Original from the University of California; Digitized July 31, 2008 ---> }}</ref> in the earth sciences, especially geology and sometimes '''barrier range''' (more common as a geography term) describing the existence of gross landforms describing long ridgelines which are particularly difficult to pass, ''especially in the context of being on foot'' or dependent upon other forms of animal powered transportation systems, in mountainous and sometimes hilly terrains.

''Barrier ridges'' such as the steep rising slopes or escarpments of the Allegheny Front, separating the ridge-and-valley Appalachians from the drainage divides of the uplands of the Appalachian Plateau. The ridge and valley region is filled with a succession of nearly impassible ridges from Northern Georgia, along the Appalachian chain all the way to Maine.<!-- Even in modern times, passage up through gaps from the Columbia Narrows transportation corridor between the Potomac River in Maryland to the Monongahela or Allegheny river valleys via the Mohawk River Valley, and then turns . --->

== Notes == {{notelist}}

==References== {{reflist}}

==External links== *{{Commons category-inline}}

Category:Geography terminology Category:Landscape Category:Landforms