puits (1) modèle (1) karst (1) érosion (1) enrichissement (1) dissolution (1) Afrique (1) Afrique (1) Dissolution (1) Origin (1) Volcanic ash, tuff, etc (1) Sahara (1) Rings (1) Magmatism (1) Karst (1) Holes (1) Fluids (1) Expression (1) Example (1) Erosion (1) Cuestas (1) Contemporary, The (1) Breccia (1) Africa (1) Centimeter (1) Shapes (1) Structure (1) Origin (1) Erosion (1) karst (1)