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[hahrd-pan] /ˈhɑrdˌpæn/
any layer of firm detrital matter, as of clay, underlying soft soil.
Compare caliche, duricrust.
hard, unbroken ground.
the fundamental or basic aspect of anything; solid foundation; underlying reality:
the hardpan of mathematical theory.
1810-20, Americanism; hard + pan1 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for hardpan
  • When small lakes dry up, they leave a salt crust or hardpan.
  • The hardpan layer, consisting of cemented limestone and slag, was located between the second granular layer and the subgrade.
  • The subgrade that was visible at the edge of the hardpan was moist clay.
  • Small, light equipment was used to avoid damaging the hardpan layer located below the vernal pools.
  • The valley portion is characterized by sandy loam which is underlain at a shallow depth in many places with hardpan.
  • Deep test pit profiles are evaluated to identify restrictive layers such as groundwater, hardpan and ledge rock.
  • If the hardpan is encountered, use a skid steer loader to remove the hardpan.
  • Replace hardpan ceiling panels and grid system with new acoustical ceiling tiles and heavy duty grid system.
  • These include bouldery sediment called till by geologists, but more commonly called hardpan.
  • Occasional areas of clay and hardpan are interspersed throughout the stream.
British Dictionary definitions for hardpan


a hard impervious layer of clay below the soil, resistant to drainage and root growth
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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hardpan in Science
A hard, usually clay-rich layer of soil lying at or just below the ground surface, in which soil particles are cemented together by silica, iron oxide, calcium carbonate, or organic matter that has precipitated from water percolating through the soil. Hardpans do not soften when exposed to water. Also called caliche.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Article for hardpan

calcium-rich duricrust, a hardened layer in or on a soil. It is formed on calcareous materials as a result of climatic fluctuations in arid and semiarid regions. Calcite is dissolved in groundwater and, under drying conditions, is precipitated as the water evaporates at the surface. Rainwater saturated with carbon dioxide acts as an acid and also dissolves calcite and then redeposits it as a precipitate on the surfaces of the soil particles; as the interstitial soil spaces are filled, an impermeable crust is formed.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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