Bogoslof reported activity

Event Name : Bogoslof 1883/8

Start:	August 17, 1883 ± 5 Months	Observed
Stop:	1895 ± 2 Years	Observed

Lava dome:
Island-forming:
Submarine:
"Fire", "Glowing", or incandescence:

Eruption Type:	Explosive
Duration:	About 12 years
Eruption Product:	basalt
MaxVEI:	3
Chem	Yes
Modal	Yes
Other	mafic

Description: The first indicator of this eruption was from residents of Unalaska, who first noticed steam rising from the ocean somewhat north of Ship Rock in 1882 (Merriam, 1901). In the fall of 1883, the eruption of Bogoslof was evident. The new island created by this eruption was called New Bogoslof or Grewingk, and is now called Fire Island (Miller and others, 1998). Miller and others summarizes as follows: "In 1884 the cone (presumably the dome was destroyed) had a diameter of 1 km, a craggy profile, and pinnacles that reached an altitude of about 150 m (Byers, 1959). In May of that year, officers of the revenue Marine steamer Corwin examined the Bogoslof group. They found Ship Rock, Old Bogoslof, and New Bogoslof connected into a single land mass by bars of volcanic debris and sand-bouldered beaches. Second Lieutenant J.C. Cantwell observed 15 separate vents on the upper third of New Bogoslof cone issuing jets of steam with great force and regularity; thick sulfur deposits surrounded most of the vents, and the temperature in a crack near the summit was estimated to exceed 260 degrees C. Great quantities of fine ash coated the slopes, but little coarse ejecta of flow lava was encountered (Henning and others, 1976). In 1895, New Bogoslof was still steaming vigorously, and was a flat-topped structure about 90 m high, separated by several hundred meters of open water from Old Bogoslof. By 1897 New Bogoslof had cooled (Byers, 1959).

Further details about the eruption are available from many sources; some of the most prominent accounts are summarized below.

Merriam (1901) wrote: "At the time of its discovery, September 27, 1883, by Captain Anderson of the schooner "Matthew Turner", it was in active eruption, throwing out large masses of heated rock and great volumes of smoke, steam, and ashes, which came from the apex and from numerous fissures on the sides and base, some of which were under the water-line. Large boulders were shot high in the air, which descending and striking the water, sent forth steam and a hissing sound. After nightfall fire was observed on the island. A month later Captain Hague of the schooner "Dora" approached it within a mile. He is quoted as saying that black smoke, like that from burning tar, was issuing from it, that it threw out flame, smoke, and red-hot rocks; and that, among the sea-lions observed near by were a number which had been scalded so that the hair had come off. He thinks many were killed. From the descriptions given him by Captain Anderson and Captain Hague, Professor George Davidson, of San Francisco, made a drawing, reproduced on page 206 of this article, representing the new volcano in the fall of 1883. Its height was estimated at from 800 to 1,200 feet. On October 20th of the same year the inhabitants of Unalaska were startled by an ominous black cloud, which appeared in the north and grew rapidly until it overspread the entire heavens and cut off the light of the sun. It then settled down very low and the air became dark like night. It finally broke and disappeared in a shower of ashes, which covered the ground and the houses, and adhered to the windows so that it was impossible to see through them. The first landing on New Bogoslof was made by the officers of the Revenue steamer Corwin (Captain M.A. Healy) on May 21, 1884, nine months after its discovery. Its altitude was found to be about 500 feet. No crater was discovered, but there was a 'great fissure,' the interior of which could not be seen owning to the steam, fumes of sulphur, and heat, which rendered entrance into it extremely dangerous if not impossible."

Merrill (1889) reports that the composition of the ashes which fell on Unalaska and the composition of volcanic samples collected from this eruption are so similar as to definitively state that the October 20, 1883 Unalaska ash came from Bogoslof.

Byers summarizes the remaining years of this eruption as follows: "In 1891, Merriam (1901, p. 313) visited the Bogoslof Islands and found steam and sulfur fumes escaping with a roaring noise from the principal fissure of New Bogoslof. An open channel separated Old and New Bogoslof. In 1895 when Becker and Dall (Becker, 1989, p. 26; Merriam, 1901, p. 317) visited the Bogoslof Islands, New Bogoslof was still steaming 'vigorously, though not violently' and had also been changed to a flat-topped island about 300 feet in altitude. Later reports in 1897 and 1899 by passing mariners indicate that New Bogoslof or Grewingk Island had finally cooled (Merriam, 1901, p. 319-320)."

Newhall and Melson (1983) estimate the volume of the lava dome produced in these eruptions to be about 40x10^6 cubic meters.