1 m 3 per day) but it has maintained a liquid lava lake in its crater since before 1972. At present it has a negligible rate of lava eruption ( c. It is at higher latitude than any other active volcano above sea level, and is situated in an aseismic intraplate region. The seismic and infrasonic signals were all of the short period Alpha type, reported by Shibuya in 1984, reflecting the small but increasing area of the lava lake.Įrebus is a unique volcano. This reflects the smaller seismic amplitudes, and consequently later readings of emergent onsets at the more distant stations. The eruptions were not randomly distributed, but were clustered in the periods 00-02 and 08-14 hours UT.Īs in 1986/7, the TV explosion instant was earlier than the intercept time of P-waves (at zero distance) by 0.69☐.33 second, but the apparent velocity of P was lower, at 1.77☐.42 km/s. The total TV view time of the crater was 435 hours in 38 days, an average of 11.4☙.2 hours per day, and the average interval between eruptions was 4.03 hours. By 3 January, 108 eruptions had been videotaped at the Scott Base receiving station, and the recordings from the Erebus seismic net had been played back, and later analysed for the 27 eruptions which were seen to eject bombs. The explosions were weaker than in 1986/7, but the lava lake was larger, and was L-shaped rather than round as before. The quality of the pictures was also improved by changing the lens from 16 to 25 mm, and raising the transmitter antenna. TV surveillance of the Erebus lava lake was restored to full operation on 17 November 1987 by replacing the camera box, the window of which had become opaque by etching in volcanic gas.
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