Anak Krakatau, which is roughly halfway between Java and Sumatra in Indonesia’s vast island chain, has been erupting since late on Friday.

Mount Anak Krakatau has erupted since late on Friday, with volcanic ash disrupting hundreds of flights as Indonesia faces a string of natural disasters across the archipelago.

The suspension of flight operations at Soekarno-Hatta International Airport, extended several times, has affected more than 900 flights, according to Indonesia's transportation…