planet

Laterite

The orange-red soil characteristic of the wet tropics, formed when year-round heavy rain leaches out nearly everything soluble and leaves a residue rich in iron and aluminium. Iron oxides give it that brick colour. For paleontology, laterite is bad news: water percolating through rotting leaf litter carries organic acids, routinely below pH 5, and bone mineral - calcium phosphate - dissolves in exactly those conditions. An unburied skeleton in laterite does not degrade; it disappears.