a second terrifying eruption from the calbuco volcano in southern chile has forced over 4,000 to leave their homes .
the cities of puerto varas and puerto montt are covered in ash and locals are becoming frightened for their health .
yesterday 's blast , which shot ash six miles into the air , was the first since 1972 and the first major one since 1961 .
no one is thought to have died from the two explosions but chile 's president has declared a state of emergency .