Indonesia on Monday raised flight warnings around the Mount Sinabung volcano on Sumatra Island to their highest level after it sent a towering plume of ash more than 7 kilometers into the air, its biggest eruption this year. Sinabung, which has been rumbling since 2010, is about 75 km southwest of Kualanamu International Airport in Medan. More than a dozen people were killed and thousands were evacuated when Sinabung erupted in 2014. Indonesia is home to around 130 volcanoes due to its position on the “Ring of Fire”, a belt of tectonic plate boundaries circling the Pacific Ocean where frequent seismic activity occurs. Mount Agung, a volcano on Bali Island, erupted again last Tuesday after its first volcanic activity in August 2017 just days after the authorities lowered the alert status of the volcano from level 4