"1991 eruption" . "second largest volcanic eruption of the 20th century" . . "1991 eruption of Mount Pinatubo" . "Mount Pinatubo" . "1991" . "eruption of Mount Pinatubo" . . . "Mount Pinatubo in 1991" . . . . "since 1991" . . . "erupted violently in June 1991" . "its eruption" . "the second-largest terrestrial eruption of the 20th century" . "colossal eruption" . . "the colossal eruption of Mount Pinatubo" . "erupted on June 12, 1991" . . "major volcanic eruption" . "Mount Pinatubo eruption in June 1991" . "2nd largest eruption in the 20th century" . "Pinatubo eruption" . "an eruption in 1991" . "climactic eruption of Mount Pinatubo" . . "erupted on 12 June 1991" . "1991 Pinatubo eruption" . . "Mount Pinatubo eruption in 1991" . "volcanic eruption" . "volcanic eruption of Mount Pinatubo in 1991" . . . . "a major eruption" . "second largest terrestrial eruption of the 20th century" . . . . "Second largest eruption of the 20th century" . "Mount Pinatubo eruption" . "eruption" . "eruption of Mount Pinatubo in June 1991" . "1991 Mt. Pinatubo eruption" . . . "1991 eruption of Mount Pinatubo" . "Mount Pinatubo 1991" . . "erupted" . "major eruption in 1991" . . "eruption of Mount Pinatubo in 1991" . "erupts" . . . "1991 Mount Pinatubo eruption" . "15 June 1991" . .