Bude is situated on upper Carboniferous strata. There are massive sandstones alternating with (usually) much thinner shales. The strata are (famously) much-contorted into folds. This probably happened deep inside the crust during the Armorican mountain-building phase (Variscan orogeny) to the south of what is now Cornwall. A great place to see the folding is from the descending coast road from Crackington to Millook (make sure your brakes are working). These rocks are not calcareous and would generally lead to fairly acid, poorly-drained soils, and the culm grasslands round here are on this formation or on alluvium adjacent to it. The sands around Bude and Widemouth are high in shell content, and any area subject to blown sand may have less acid soils as a result. Shell-rich sand from the coast near Bude was the reason Bude Canal was built. The shell-sand was transported inland to sweeten the acid, clay soils in the hinterland.