Plural of hardpan; layers of hard, compacted clay or subsoil that water cannot easily penetrate.
Compound of 'hard' and 'pan' (a shallow, flat container, but here meaning a geological layer). The term emerged in soil science and geology to describe resistant subsurface layers.
Farmers and gardeners curse hardpan because it prevents water drainage and root growth—ironically, it's usually formed by years of heavy machinery compacting soil, meaning human activity accidentally creates geological obstacles.
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