Caliche - How IT Forms

How It Forms

Caliche generally forms when minerals are leached from the upper layer of the soil (the A horizon) and accumulate in the next layer (the B horizon), at depths of approximately three to 10 feet under the surface. It generally consists of carbonates in semiarid regions, while in arid regions, less-soluble minerals will form caliche layers after all the carbonates have been leached from the soil. The calcium carbonate that is deposited accumulates, first forming grains, then small clumps, then a discernible layer, and finally, a thicker, solid bed. As the caliche layer forms, the layer gradually becomes deeper, eventually moving into the parent material, which lies under the upper soil horizons.

However, caliche can also form in other ways. It can form when water rises through capillary action. In an arid region, rainwater will sink into the ground very quickly. Later, as the surface dries out, the water below the surface will rise, carrying dissolved minerals from lower layers upward with it. This water movement forms a caliche that tends to grow thinner and branch out as it nears the surface. Plants can contribute to the formation of caliche, as well. The plant roots take up water through transpiration, leaving behind the dissolved calcium carbonate, which precipitates to form caliche. It can also form on outcrops of porous rocks or in rock fissures where water is trapped and evaporates. In general, caliche deposition is a slow process, but if enough moisture is present in an otherwise arid site, it can accumulate fast enough to block a drain pipe.