Figure 3. Kilauea summit SO₂ emission rates in metric tons per day from June 1979 through 1997. Summit emissions increased with the onset of the 1983 Pu‘u ‘Ō‘ō eruption. Another increase is seen in early 1987, and summit emissions have declined from an average of 410 mt/d for February 1987 to 140 mt/d for February 1997.