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The Pamphlet Collection of Sir Robert Stout: Volume 67

General Account of the Eruption

General Account of the Eruption.

When it is remembered that the eruption of Mount Tarawera was quite unexpected, and that it occurred in the middle of the night in a hilly country sparsely inhabited, it will be allowed that a strictly correct narrative of the eruption is impossible. Nevertheless we are of opinion that the following gives a fairly accurate account of the sequence of events that took place.

Commencement of the Eruption.—The night of Wednesday, the 9th June, 1886, was fine and starlight, the moon in her first quarter, and it was nearly calm. At 12.30 a.m. on the 10th earthquakes commenced, slight at first, but increasing in intensity. At 1.15 or 1.20 a.m. Wahanga broke out with a flash followed by an explosion, after which everything remained quiet until 1.45 a.m., when the main eruption commenced, probably from Ruawahia. At 2.10 a.m. there was a violent earthquake, and immediately afterwards Tarawera broke out with a loud roar; and at 2.30 a.m. the whole mountain from Wahanga to Tarawera was in violent eruption. The column of steam was at first continuous, but afterwards broke up into seven or more distinct columns. These spread slowly out at the top into abroad black cloud. Forked lightning darted out from the column, and brilliant electrical scintillations illuminated the margin of the cloud. Showers of red-hot stones were shot upwards like rockets, and fell outwards in all directions; the column was also lighted up by the reflection from the red-hot rocks below. The red-hot stones were seen distinctly at Gis- page break
Plate IV.

Plate IV.

Te Hape O Toroa. 16TH June 1886.

From a Photograph by C. Spencer, Tauranca.

page 11 borne—seventy-five miles distant—and the height to which they ascended was calculated by Archdeacon Williams to be 32,000ft., which, however, seems to be excessive.

At 2.30 a.m. another black (one observer says yellow) steam column arose straight up from near Lake Okaro, and attained an elevation considerably greater than that from Mount Tarawera. All observers agree that this column came from a point much to the west of Rotomahana. It was thought to proceed from Kakaramea, but it is now known that the southernmost crater is considerably to the north of Kakaramea, but on the direct line between Kakaramea and Wairoa. At 3.30 a.m. very violent earthquakes and eruptions commenced, which were probably caused by the outbreak of Rotomahana. It is impossible to ascertain this with certainty, as no one was in a position to observe this portion of the line; but the evidence obtained by the boating party that visited Te Ariki on the 14th June is strongly confirmatory of the opinion that some of the Okaro craters were active before those of Rotomahana. The boating party found the Kaiwaka Creek, which formerly drained Rotomahana, to be dry, and with Avails 20ft. to 25ft. high; the lower; portion formed of scoria, stones, and white ash, covered by a layer of mud from 2ft. to 5ft. thick. The bed of the creek was dry and firm near Lake Tarawera, but higher up the bottom got soft. The layer of mud had been cut through as well as the scoria, so that the stream must have flowed after the mud had been deposited. This, therefore, must have taken place before the eruption of Rotomahana, which dried up the steam.

The steam columns from Rotomahana and Okaro are not reported to have been accompanied by red-hot stones, neither were they lit up by reflections from red-hot rocks. They spread slowly to the north, and obscured the cloud from the mountain.

Decline of the Eruption.—At 5.30 a.m. on the 10th the crisis of the eruption was over, although heavy earthquakes continued until 6 a.m. The pillar of steam from Mount Tarawera was seen at 9 a.m., and thunder and lightning-flashes continued to 10 or 11 a.m. Mrs. Blyth, who at this time was on the Kaingaroa Plains trying to get from Galatea to Rotorua, states that there was then no eruption from Wahanga or from Ruawahia, only at Tarawera proper, as well as at Rotomahana and Okaro. At 4 or 5 p.m. the eruptions from Rotomahana and Okaro were much less, although Tarawera was still very active and making a great noise. It continued in that state until about midnight.

page 12

On the morning of the 11th only small quantities of steam were issuing from the mountain, but the craters of Rotomahana and Okaro continued to throw out immense quantities of steam together with sand and stones. On Sunday, the 13th, the steam column was observed by Mr. Humphries at New Plymouth—120 miles distant—and calculated to reach 25,000ft. above the sea Stones were ejected from these craters for ten or twelve days but with diminished quantities of steam; and from that time to the end of our visit the amount of steam remained practically the same. On the 8th July, and again on the night of the 12th slight spasmodic increases in violence of the Rotomahana craters took place.

It thus appears that the eruption of the mountain began at 1.15 a.m., continued for about twenty-three hours, and then rapidly declined. The eruptions from the flat commenced at 2.30 a.m., were most violent from 3.30 to 5.30 a.m., them slowly decreased, but continued for ten or twelve days to eject solid materials, and, with the exception of the southern crater, they were during our visit gigantic fumaroles.