a subsurface indurated horizon. Red-brown hardpans in Australia are characterised by the presence of a porous matrix, commonly red-brown in colour, cemented by silica (usually hyalite), in a variety of transported or residual host materials.
A term that should be avoided by the engineer. Originally, it was applied only to a soil horizon that had become rocklike because of the accumulation of cementing minerals. The name implies a condition rather than a type of soil.
A hardened soil layer in the lower or in the horizon caused by cementation of soil particles with organic matter or with materials such as silica, sesquioxides, or calcium carbonate. The hardness does not change appreciably with changes in moisture content, and pieces of the hard layer do not crumble in water. cf. caliche.
In soil science, agriculture and gardening, hardpan is a general term for a dense layer of soil, residing usually below the uppermost topsoil layer. There are different types of hardpan, all sharing the general characteristic of being a distinct soil layer that is largely impervious to water. Some hardpans are formed by deposits in the soil that fuse and bind the soil particles.