Besides the cataclysmic YTT eruption, one of the most spectacular aspects of Toba’s history involves the uplift of Samosir and Uluan. Throughout geologic history, large silicic calderas have experienced intracaldera uplift, known as resurgence. This phenomenon, first described by van Bemmelen at Toba, has been attributed to either recharge of the shallow sub-caldera magma reservoir or a period of regional relaxation and subsidence (countereffect of Batak Tumor formation) that drives remnant magma surfaceward, uplifting the caldera floor.