Observation of on going eruption at the Miyake-jima volcano from helicopter, on January 15, 2001

Photos and texts by Isoji MIYAGI at the Geological Survey of Japan;
Observations by I.Miyagi and Prof. Oshima at the Univ. Tokyo;
Helicopter by Tokyo Metropolitan Police Department.

Topics:
With thermal imaging device, I measured temperature of the summit vent.
# QuickTimeMovieFiles are available.
The island was covered with snow (the first snow).


Helicopter of the Tokyo Metropolitan Police Department

Left: Getting on to the helicopter (Oo-Tori(means; big-bird)-1st, Bell 412) at Tokyo heliport.
Right: Getting on to the helicopter (Oo-Tori-5th) at Kozu island airport.

Left: I would like to say thank you to all the helicopter crew for their efforts.
Right: Mt. Fuji. View is very excellent through the flight.

Miyake-jima of the snow scene

It was snowing in sky when beginning to ovserve the island. This is the first snowfall in the series of helicopter observation (Prof. Oshima said). Temperature in sky was below 8 from zero (in Celsius).

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Left picture: One of the side door of the helicopter is opened completely for the infrared observation.
By opening the door, my body instantly cools, and the movement of my finger has worsened. It will be serious if I drop the thermal image device (what kindly borrowed from Dr. Matsushima in GSJ), though there are virtually no people injured in this island (all the people have been evacuated, except for few peoples who are working daytime for minimal necessary maintenance), because it cost about 5,000,000 yen.

A large amount of smoke goes out as usual, but it is not too active compared with December 27, 2000.

The smoke was white and a pale coloured mist was seen under that. The top altitude of smoke was 4000 feet (according to an altimeter of the helicopter), flowed in the direction of "Miike district" by the wind from the west. The ash fall was not admitted.

The left picture: The crest is seen from the northeast sky of the island. Because light like blue was scattered by the sulfur dioxide in smoke, the sunlight (reflected by the surface of the sea) looks red.
The left picture: The crest is seen from the southeast sky of the island. Because smoke is filled, the inside in the sinking caldera is not seen at all in the naked eye.

Appearance of the summit caldera (with radius of 1 mile) seen from north sides (panorama photograph).

Appearance of the summit caldera seen from the south of (panorama photograph). There was pale coloured fog "Sulfuric acid mist", under main smoke, and the smoke was thrown by western wind in the direction from the "Miyake-jima airport" to "Miike district".

Why does the gas go out so much? ?
Reference (sorry mostly in Japanese):

  • Opinion concerning the activity in 2000 Miyake-jima volcano A model to which degassing activity occurs because of magma. (by GSJ; sorry in Japanese)
  • As for the transition of the degassing activity of the Miyake-jima volcano after September, 2000 (by GSJ; sorry in Japanese)
  • Sulfur dioxide discharge rate of Miyake-jima volcano measured by COSPEC (by K.Kazahaya at the GSJ; in English)
  • Classification of ash particles from the Miyake-jima volcano 2000 eruption (by I.Miyagi at the GSJ; in Japanese)

    Temperature measurement of fumaroles with a thermal imaging device

    The highest temperature which had been observed by measuring the fumarole with the thermal image was about 314 degree Celsius.

    Please note that actual temperature could be higher than this figure.

    This is due to a very bad condition for the temperature measurement using infrared emission at that time. Fumarole vents are located at the bottom of the summit caldera filled with dense smoke. This smoke will absorb or scatter the infrared ray from the the heat source (fumarole vent).

    Thus, even if the fumarole vent has a temperature of, for example, several hundreds degree Celsius, we could observe nearly atmospheric temperature, as a consequence of infrared radiation of the smoke itself, or that of cool mount body reflected by the smoke.


    Looking down around the marked area:

    (High Quality Movie; 8.2M)

    (Low Quality Movie; 1.6M)

    Click to download QuickTimeMovie

    Explanations:
    HT: Maximum temperature of current image.
    P1: Temperature at cross mark "1".
    P2: Temperature at cross mark "2".
    P3: Temperature at cross mark "3" (not shown).
    # It is confirmed that the clock is 2 minute 10 seconds faster than actual time.
    Reference: Temperature of summit vent, 19 September, 2000 (by JMA and GSJ)


    # You need QuickTime viewer to work with QuickTimeMovie.

    Rift (cracks) arounding the summit caldera

    Western-south of the caldera edge.

    The crack of the southern part of the caldera rim which had been reported on 25th December, 2000 when Dr. nakano was an observer, was able to be confirmed. In the crack, the inside is considerable loss, though there is no extending appearance. I think the inside dropped sharply.


    If you have questions about this page, contact Isoji MIYAGI