hardpan

[hahrd-pan] /ˈhɑrdˌpæn/

noun

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.

Origin

1810-20, Americanism; hard + pan¹

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

hardpan

/ˈhɑːdˌpæn/

noun

a hard impervious layer of clay below the soil, resistant to drainage and root growth

hardpan in Science

hardpan

(härd'pān')
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.

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.

Learn more about hardpan with a free trial on Britannica.com