Mount Anak Krakatau volcano spews hot ash during an eruption as seen from an Indonesian Navy ship at Sunda strait in Banten on December 28, 2018. The volcano continues to erupt nearly a week after it caused a devastating tsunami that killed over 400 people. [Photo: Antara Foto via VCG/Muhammad Adimaja]

Mount Anak Krakatoa erupts as seen from an Indonesian Navy ship at Sunda strait in Banten on December 28, 2018. [Photo: Riau Images/Barcroft Images via VCG]

The Anak Krakatau volcano erupts, spewing a massive cloud of hot gasses and ash on December 28, 2018 off the coast of Banten, Indonesia. Flights have been rerouted and the alert level for the Anak Krakatau Volcano raised to the second highest level as it continues to erupt sending massive clouds of ash into the air nearly a week after the volcano caused a deadly tsunami killing over 400 people. [Photo: Getty Images via VCG/Ed Wray]

Mount Anak Krakatau volcano spews hot ash during an eruption as seen from an Indonesian Navy ship at Sunda strait in Banten on December 28, 2018. [Photo: Antara Foto via VCG/Muhammad Adimaja]