They're soils, but they're special soils [1] that can harden to a brick-like consistency (called a "duricrust") upon being dried out and exposed to the air [2,3

They're soils, but they're special soils [1] that can harden to a brick-like consistency (called a "duricrust") upon being dried out and exposed to the air [2,3]. The unusual durability of such soils has made them a target for study in their own right, using cosmogenic isotopes to estimate erosion rates over Myr timescales (which turn out to be incredibly slow; 0.16–0.54 m/Myr) [4] [1] https://www.cambridge.org/core/journals/clay-minerals/article/minerals-in-the-clay-fraction-of-brazilian-latosols-oxisols-a-review/D7F78269F40171B35BDF5FFCFD9EB5B7 https://www.cambridge.org/core/journals/clay-minerals/articl... [2] https://en.wikipedia.org/wiki/Duricrust https://en.wikipedia.org/wiki/Duricrust [3] https://www.sciencedirect.com/science/article/pii/S0169136817309587 https://www.sciencedirect.com/science/article/pii/S016913681... [4] https://www.sciencedirect.com/science/article/abs/pii/S0012821X1200101X https://www.sciencedirect.com/science/article/abs/pii/S00128...