The bulk of the volcano is formed by lava flows, along with volcaniclastic rocks, with dacites and pyroclastics lying on top of the Cretaceous-Eocene basement. These loose rocks formed by erosion, explosive activity and hot avalanches and are deposited in a large apron at the base of the volcano that extends over away from the central vents. Several fans of pyroclastic material, cemented by andesitic tuffs, surround the base of Taftan. Ignimbrites and pyroclastic flows are also present, including breccias, nuee ardentes and tuffs. Volcanic rocks cover a surface of . There is also evidence of southeastern migration of the craters of Taftan, with Anjerk and Sardarya being more westerly vents. These preceding centres have left andesitic lava flows that are partially dissected and agglomerates. The existence of a caldera at Taftan has been inferred. The table mountain Takht-i-Rostam south of Taftan may be the remnant of a basalt extrusion, but it doesn't appear to be related to Taftan. A magma chamber may lie beneath the volcano.