The 16-km-wide Tengger caldera is located at the northern end of a volcanic massif extending from Semeru volcano. The massive volcanic complex dates back to about 820,000 years ago and consists of five overlapping stratovolcanoes, each truncated by a caldera. Lava domes, pyroclastic cones, and a maar occupy the flanks of the massif. The Ngadisari caldera at the NE end of the complex formed about 150,000 years ago and is now drained through the Sapikerep valley. The most recent of the calderas is the 9 x 10 km wide Sandsea caldera at the SW end of the complex, which formed incrementally during the late Pleistocene and early Holocene.
The Tengger Caldera is also known as the Sandsea Caldera. It is likely named Seasand (Sea of Sand) Caldera, because the caldera holds vast areas of sand. The caldera contains an overlapping cluster of post-caldera cones was constructed on the floor of the caldera within the past several thousand years. .