The large magma chamber under Tambora had been drained by pre-1815 eruptions and underwent several centuries of dormancy as it refilled . Volcanic activity reached a peak that year , culminating in the eruption . With a Volcanic Explosivity Index of 7 , the eruption was the most devastating in recorded history . The explosion was heard on Sumatra island , more than away . Heavy volcanic ash rains were observed as far away as Borneo , Sulawesi , Java and Maluku islands , and the maximum elevation of Tambora was reduced from about to . Although estimates vary , the death toll was at least 71,000 people . The eruption caused global climate anomalies in the following years , while 1816 became known as the " year without a summer " due to the impact on North American and European weather . In the Northern Hemisphere , crops failed and livestock died , resulting in the worst famine of the century
year without a summer
Year Without a Summer
Mount Tambora