The concave profile, a hyperbolic sine curve of the volcano is due to the balance between erosion and eruption, defined by the angle of repose of ash. The steepest upper slopes of the volcano reach an average slope gradient of 75%, while the lower foot slope is only an average of 3%. The volcanic crater is about 250 m in diameter. At least 85 lava flows have been identified, and consist mainly of 'A'ā augite-hypersthene-andesite, generally fed from the crater. Pyroclastic flows, characterized as a St. Vincent nuee' ardente, leave behind block and ash deposits, and breadcrust bombs in an ash and lapilli matrix. The farthest flow reached 8.5 km along Fidel Surtida, Santo Domingo. Mayon lahars were formed by rainstorms during eruptions, or by torrential rain afterwards. Averaging 230 m in height and 710 m in diameter, 7 cinder cones are found on the southern and southwestern lower slopes. Composed of olivine-augite basalt, these cones have an angle of repose of 34%, with Ligñon Hill as an example.