The ice cores indicated a large sulfate spike, accompanied by tephra deposition, around 1257-1259, the largest in 7,000 years and twice the size of the spike due to the 1815 eruption of Tambora. In 2003, a dense rock equivalent volume of was estimated for this eruption, but it was also proposed that the eruption might have been somewhat smaller and richer in sulfur. The volcano responsible was thought to be located in the Ring of Fire but could not be identified at first; Tofua volcano in Tonga was proposed at first but dismissed, as the Tofua eruption was too small to generate the 1257 sulfate spikes. A volcanic eruption in 1256 at Harrat al-Rahat near Medina was also too small to trigger these events. Other proposals included several simultaneous eruptions. Estimated diameters and positions of the calderas left by the eruption ranged from , close to the equator and probably north of it.