The eruption is estimated to have had a Volcanic Explosivity Index of 7 . It had roughly four times the energy of the 1883 Krakatoa eruption . An estimated of pyroclastic trachyandesite was ejected , weighing approximately 1.4 × 1014 kg . This has left a caldera measuring across and deep . The density of fallen ash in Makassar was 636 kg/m3 . Before the explosion , Mount Tambora was approximately high , one of the tallest peaks in the Indonesian archipelago . After the eruption of 1815 , the maximum elevation has been reduced to
1883 Krakatoa eruption
1883 eruption of Krakatoa
Mount Tambora