Colo [Una Una]

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  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 0.17°S
  • 121.608°E

  • 507 m
    1663 ft

  • 266010
  • Latitude
  • Longitude

  • Summit

  • Volcano

The Global Volcanism Program has no activity reports for Colo [Una Una].

The Global Volcanism Program has no Weekly Reports available for Colo [Una Una].

Index of Monthly Reports

Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

07/1983 (SEAN 08:07) Pyroclastic flows devastate island; clouds to stratosphere; evacuations prevent large death toll

08/1983 (SEAN 08:08) Continued explosive activity seen on satellite images; numerous magnitude 5 earthquakes

09/1983 (SEAN 08:09) Satellite observations of July-August eruption clouds

10/1983 (SEAN 08:10) July- August explosion times, plume heights, and photos

08/1987 (SEAN 12:08) Plume seen on satellite imagery

10/1987 (SEAN 12:10) 14 July plume may have been weather cloud

Contents of Monthly Reports

All information contained in these reports is preliminary and subject to change.

All times are local (= UTC + 8 hours)

07/1983 (SEAN 08:07) Pyroclastic flows devastate island; clouds to stratosphere; evacuations prevent large death toll

An explosive eruption produced pyroclastic flows that destroyed most homes, vegetation, and animal life on 40 km2 Una Una Island and probably injected tephra into the stratosphere. Initial activity prompted evacuation of everyone on the island before the devastating explosions.

The eruption was preceded by seismicity that increased from 9-11 felt events/day on 8 July to 30-40/day on 15 July. The number of recorded events was 33 on 14 July, increasing the following days to 49, 53, and 73 then to an average of more than 90/day 18-21 July. The strongest earthquake was felt 400 km away on 18 July. That morning, a 1-km column of ash and incandescent material was ejected. AFP reported that a strong explosion occurred 19 July, and thick gray clouds containing incandescent tephra were visible from Ampana, more than 100 km to the S, the next day.

By the 20th, almost all houses and buildings in the eight villages near the volcano had been destroyed and nearly half of the residents of the island had been evacuated. All had left by the time of a major explosion on 21 July at 1623 that subjected 80% of the island to temperatures of up to 200°C. Tephra as large as 5-10 cm in diameter fell near a VSI observation vessel and the monitoring team reported flames on parts of the island. A government geologist estimated that all 700,000 coconut trees and all livestock on the island must have been burned, probably by pyroclastic flows. Ash darkened much of the region. People in Falu, 250 km away, were forced to protect themselves from ashfall until late 23 July. A VSI field party arriving on the island 22 July at 0100 felt ten earthquakes during their 15-hour stay and observed a 1.5-km eruption column at 1649.

On 23 July at 2055, a British Airways jet (en route from Singapore to Perth) flying at 10.6 km altitude encountered an eruption cloud at 1.4°S, 120.71°E, about 150 km S of Una Una (figure 1). Pilots noted a volcanic smell, lack of visibility, and St. Elmo's Fire around the windshield. The aircraft returned immediately to Singapore and suffered no damage. On 24 July at 1930, a satellite image showed a cloud about 120 km wide, extending about 600 km S from Una Una. Earlier in the eruption, weather clouds had obscured the Una Una area. Press reports quoted a local government official who said that 80% of the island was covered by volcanic clouds on 24 July, burning vegetation and destroying trees. On 26 July at 0000, the Japanese GMS satellite showed what appeared to be a dense eruption column rising from the island. On the next image, two hours later, a fan-shaped plume was visible, probably in or near the stratosphere. High-altitude material was blowing SW and W, while low and mid-level debris was drifting slowly S to SSE.

Figure 1. Portions of three GMS images showing the expansion of the cloud produced by the explosions of 23 July 1983, when hot avalanches devastated Una Una island shortly after residents had been evacuated. An arrow points to the eruption plume on each image. Land areas are outlined, from Sumatra and the Malay Peninsula at left to Timor and Halmahera at right. Image scans began at 1631 (upper left), 1831 (lower left), and 1931 (lower right), with "x" marking position of aircraft 84 minutes later. Courtesy of Yosihiro Sawada. [Originally from 8:9.]

On 28 July at 0200 the GMS satellite showed a small plume over the island. By 0500 a plume about 60 km wide extended about 200 km WSW from the volcano. The plume appeared denser at 0800 and by 1100 vigorous activity fed a cloud that reached 118 E and at least 13.5 km altitude. At 1400 the plume stretched about 500 km to the WSW and was very dense within 250 km of the volcano. Temperatures and wind directions at the tropopause (15 km altitude) were consistent with the plume's direction of movement and coldest temperature (-76°C) from a NOAA 7 image at 1430 (figure 2). By the next image, at 2000, the plume had dissipated. The GMS satellite showed the beginning of another eruptive episode on 30 July at 1630. At 2000, a NOAA 7 image contained a WSW-drifting plume, similar to the one on 28 July but not as spectacular. Feeding of this plume was continuing at 2300; it drifted SW, then W toward Sulawesi. It extended from the volcano about 200 km to 1.5°S, 119.5°E on 31 July at 0200, but was dissipating three hours later. At 2000 an image showed what appeared to be an eruption column, but little activity was visible three hours later.

Figure 2. NOAA 7 thermal infrared satellite image showing an 800-km-long eruption plume from Una Una 28 July at 1430. White areas are coldest (see gray scale at top of figure). The coldest part of the plume had a temperature of -76°C, indicating that it had penetrated the stratosphere. Courtesy of Michael Matson.

Another explosive episode first appeared on the imagery 2 August at 0500. Before activity ended at 1700, a plume had moved about 200 km to theSW and reached roughly 9-12 km altitude. A dense eruption column appeared over the island 3 August at 0000 and extended roughly 120 km to the W and SW two hours later. The plume was relatively diffuse and appeared to have reached only the mid-troposphere. Satellite images indicated that another explosion started 4 August at about 1000, feeding a plume that moved about 350 km to the NNW. The different direction of drift was the result of a weather change; this plume probably remained in the troposphere. AFP reported an eruption on 9 August at 0835 that ejected a gray plume to 3 km. No activity was evident on satellite images until 12 August at 0130, when a plume was observed that was not visible two hours earlier. At 0300, NOAA 7 data showed a dense plume, similar to that of 28 July, extending about 300 km SW to central Sulawesi.

Information Contacts: A. Sudradjat, VSI; N. Banks, HVO; M. Matson, J. Hawkins, O. Karst, and S. Kusselson, NOAA/NESDIS; AFP; Antara News Agency, Jakarta; UPI.

08/1983 (SEAN 08:08) Continued explosive activity seen on satellite images; numerous magnitude 5 earthquakes

Satellite images continued to show occasional eruption plumes through late August. After the 12 August plume described last month, activity was next observed on an image from the GMS satellite on 22 August at 1400, when a very small fairly bright area was present directly over the island, a feature typical of the initial stages of an explosive episode. This event developed rapidly with a NOAA 7 image 35 minutes later showing a bright plume extending about 60 km to the W. By 1700 (GMS data), it had moved about 120 km W from the volcano, and its leading edge had just reached the coast of Sulawesi. On the next image, at 2000, feeding from the volcano appeared to have ended and the plume was dissipating to the W. On 26 August at 1100, a GMS image showed a bright, newly-ejected plume about 40 km wide that appeared to have reached the tropopause. At 1400, a very dense high-level cloud about 80 km wide had spread W then SW about 250 km, but on a NOAA 7 image 1 hour later the cloud appeared to be dispersing and the eruption had clearly ceased by the next GMS image at 1700. On 29 August, GMS imageryshowed the beginning of an explosive episode at about 1930. By midnight, a moderately dense plume extended WSW along the equator, then turned abruptly to the SSW, reaching 120°E at 1-2°S. On the next image, at 0500, feeding from the volcano had stopped and the plume was nearly dissipated.

Government officials noted that several villages [were] completely destroyed by the eruption and that all of the island's coconut trees had been killed. All of the people living on Una Una were evacuated before the devastating explosions 23 July. Officials anticipated that it would be several years before the island would again be habitable, so residents have been resettled on other islands until they can return.

The WWSSN noted 66 events in the vicinity of Una Una beginning late 16 July. No earthquakes smaller than M 4.5 were tabulated, and most magnitudes were between 4.8 and 5.4. Of these, the 21 recorded by 20 or more stations had a mean epicenter of 0.09°S, 121.70°E (standard deviations for both latitude and longitude, 0.05°), about 15 km NE of the volcano. Depths of the same 21 events avaraged 55 km (standard deviation 7.5 km). Earthquakes recorded by the WWSSN had become less frequent by the time of the largest explosion 23 July; few were recorded after 26 July and none after 1 August. Other events in the region included single M 5.0-5.3 shocks on 27, 28, and 31 July, about 200 km ENE of Una Una at roughly 40 km depth; and M 5.5 and 5.1 earthquakes 20 and 31 July at depths of 299 and 272 km, 300 km WNW of the volcano.

Information Contacts: M. Matson, J. Hawkins, and S. Kusselson, NOAA/NESDIS; NEIC; Antara News Agency, Jakarta.

09/1983 (SEAN 08:09) Satellite observations of July-August eruption clouds

Since late August, no explosions have been reported by ground observers or seen on satellite imagery. Yosihiro Sawada searched all July and August images from the GMS satellite and provided table 1.

Table 1. Una Una eruption cloud data extracted from GMS satellite images. Data are tentative; some apparent plumes may have been weather clouds. Times are the beginnings of image scans, which are completed in about 25 minutes. Images are returned 14 times/day at intervals ranging from 30 minutes to 3 hours. New explosions are indicated in the remarks column. Data shown in parentheses are for plumes that are detached from the volcano because explosive activity had (apparently) stopped. A new plume was sometimes ejected before remnants of the previous explosive pulse had dissipated; dimensions of the old plume are then listed in parentheses below data on the new activity. Coldest temperatures at the tops of plumes are shown. Courtesy of Yosihiro Sawada.

                   (km)    (km)  (°C)
    23 Jul  1631   100      90   -74
            1801    -        -   -76
            1831   320     200
            1931   560     180
    25 Jul  2331    30      30   -70   New explosion
    26 Jul  0131   210     160
            0431  (520)   (160)
    27 Jul  1931    60      20         New explosion
    28 Jul  0131   160      20
            0431   170      50
            0631   290      70
            0731   260      40
            1031   500      70
            1331   550      60
            1631   710      80
            1831   650      70
            1931   500      30
            2331  (340)    (20)
    30 Jul  1631    80      40   -73   New explosion
            1801    -        -   -80
            1831   260     110
            1931   370     120
            2331   190      50         New explosion
                  (340)   (320)
    31 Jul  0131   250     130
            0431  (260)   (100)
            1801     -       -   -70   New explosion
            1831    60      30   -71
            1901     -       -   -71
            1931   160      50   -71
            2331  (150)    (80)
    01 Aug  0131  (160)   (110)
            0431  (130)    (50)
    02 Aug  0431    70      50   -72
            0601     -       -   -65
            0631   160      70   -63
            0701     -       -   -72
            0731   240      80   -75
            1031   420     100   -79
            1331    50      15   -60   New explosion
                  (340)   (240)
            1631    60      20   -56
                  (420)   (320)
            1831  (130)    (20)
            1931  (450)   (320)
            2331    80      30   -71
    03 Aug  0131  (120)    (60)
            0431  (110)    (20)
            0631  (130)    (15)
    04 Aug  1031    80      40   -73
            1331   150     110   -73
            1631   190     120   -63
            1831  (190)   (160)
            1931  (210)   (130)
            2331    90     100   -79   New explosion
    05 Aug  0131   170     100   -81
            0431   280     200   -73
            0601     -       -   -61
            0631   170     170   -60
            0701     -       -   -64
            0731    30      30   -70   New explosion
            1031    60      60   -61
            1331   100      90   -63
            0131    30      20   -64
    06 Aug  0131    30      20   -64   New explosion
            0431   110      60
            0631   190      90
            0731   200     130
            1631    60      50   -73   New explosion
            1801     -       -   -69
            1831   110      70
            1931  (130)    (80)
    07 Aug  1331   190      80   -75   New explosion
            1631   320     110   -79
            1801     -       -   -77
            1831   190     150   -75
            1931   240     160
            2331   150      70
    08 Aug  0131  (190)    (60)
            0431    30      15         New explosion
            0631    60      15
            0731   (70)    (20)
    10 Aug  0131    30      20         (obscure)
            0431    30      10         (obscure)
            0631    50      15         (obscure)
    11 Aug  1331   290      80   -69
            1631  (510)   (110)
            1831  (680)   (160)
    12 Aug  0131   140      60   -73   New explosion
            0431   460     100
    22 Aug  1331    20      15         (obscure)
            1631   150     110         (obscure)
            1831  (260)   (110)
            1931  (300)   (140)
    26 Aug  1331  (almost circular)    New explosion
            1631                       Cloud detected

Information Contact: Y. Sawada, MRI, Tsukuba.

10/1983 (SEAN 08:10) July- August explosion times, plume heights, and photos

A VSI team monitored the eruption from near the island [beginning 23 July, and observed 22 distinct explosions (table 2). Many, but not all of these explosions were detected by satellite (table 1).]

Table 2. Times of Una Una eruption clouds with heights estimated by VSI geologists [23 July-26 August 1983.].

    1983       TIME      HEIGHT (km)

    23 Jul     1623        10
    25-26 Jul  2325-0021    7.5
    27 Jul     0400-0605    7.5
               1500-2010    7
    28 Jul     0002-0045    8
               1630-1730    8
    30 Jul     1615-?       6
    01 Aug     1834-2000    7
    01-02 Aug  2130-0230    6
    02 Aug     0314-0600    8
               0800-0900    8
    02-03 Aug  1905-0200    5
    04 Aug     0915-1100    6
    06 Aug     1520-?       6
    07 Aug     1100-1900   10
    11 Aug     1115-1135    8
    12 Aug     0047-0147    9
    18 Aug     1013-1240   12
    22 Aug     1203-?       8
    24 Aug     2148-2220    4
    25 Aug     1847-2000    5.5
    26 Aug     1023-1139   10

Maurice Krafft visited Una Una in mid-Aug. He observed and photographed the 22 Aug explosion (table 2 and figure 3) and pyroclastic flow deposits from previous explosions (figure 4). The entire island had been devastated except for a narrow strip of undamaged vegetation and villages along the E coast.

Figure 3 Explosion photographed from the S on 22 August 1983. Pyroclastic flows from this explosion continued 500 m beyond the SSW coast of the island and 1 km beyond the NNW coast. Courtesy of Maurice Krafft.
Figure 4 Coconut trees uprooted by pyroclastic flows on the SE side of the island, photographed 19 August 1983. Pyroclastic flow deposits from the major 23 July explosion were 5 m thick on the island's SW side. A plume from the summit is in the background. Courtesy of Maurice Krafft.

Further Reference. Katili, J.A., and Sudradjat, A., 1984, The devastating 1983 eruption of Colo volcano, Una Una Island, central Sulawesi, Indonesia: Geologisches Jahrbuch, v. A75, p. 27-47.

Information Contacts: A. Sudradjat, VSI; M. Krafft, Cernay.

08/1987 (SEAN 12:08) Plume seen on satellite imagery

Imagery from the NOAA 10 polar orbiting weather satellite showed a plume that extended S then W ~200 km from Una Una on 14 July at 0708. VSI could not confirm that an eruption had occurred.

Information Contacts: W. Gould, NOAA/NESDIS; VSI.

10/1987 (SEAN 12:10) 14 July plume may have been weather cloud

Although a NOAA 10 weather satellite image on 14 July showed a cloud that extended ~200 km from the vicinity of Una Una, no reports were received of an eruption from the island, uninhabited since residents were evacuated before the paroxysmal explosion of 23 July 1983.

Yosihiro Sawada inspected 14-15 July imagery from the GMS weather satellite. By 0800 on 14 July, less than an hour after the NOAA 10 image, the cloud retained a plume-like structure, but its origin was several tens of kilometers W of Una Una. An infrared image 24 hours later showed a chain of weather clouds extending SW from several sources just W of Una Una. On the image returned three hours later, these clouds had combined to form a plume-like feature similar to the one seen the previous day. This evidence, and the absence of a reported eruption, suggested that weather clouds may have produced the 14 July plume.

Information Contacts: Y. Sawada, JMA.

Colo volcano forms the isolated small island of Una-Una in the middle of the Gulf of Tomini in northern Sulawesi. The broad, low volcano, whose summit is only 507 m above sea level, contains a 2-km-wide caldera with a small central cone. Only three eruptions have been recorded in historical time, but two of those caused widespread damage over much of the island. The last eruption, in 1983, produced pyroclastic flows that swept over most of the island shortly after all residents had been evacuated.

Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1983 Jul 18 1983 Dec Confirmed 4 Historical Observations Gunung Colo
1938 ± 10 years Unknown Confirmed 1 Historical Observations Gunung Colo
1898 May 2 1900 (?) Confirmed 3 Historical Observations Gunung Colo

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Una Una | Oena Oena | Nangoena | Tjolo, Gunung | Belerang, Gunung
Ash mantles the summit of Colo volcano after a powerful explosive eruption in 1983. The volcano forms the isolated island of Una-Una in the middle of the Gulf of Tomini in northern Sulawesi. The broad, low volcano is truncated by a 2-km-wide caldera that contains a small central cone. Only three eruptions have been recorded in historical time. The last eruption, in 1983, produced pyroclastic flows that swept over most of the island shortly after all residents had been evacuated.

Photo by M.S. Santoso, 1983 (Volcanological Survey of Indonesia).
A broad ash plume rises above Colo volcano on the island of Una-Una during the powerful 1983 eruption. Phreatic eruptions began on July 18. All inhabitants of the island were evacuated prior to the paroxysmal eruption at 1623 hrs on July 23, when pyroclastic flows devastated most of the island. Intermittent large explosive eruptions, some producing pyroclastic flows, continued until August 30, and minor ash eruptions lasted until October 10. White and sometimes gray "smoke" was reported November-December, presumably from phreatic eruptions.

Photo courtesy of Volcanological Survey of Indonesia, 1983.

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

Katili J A, Kartaadiputra L, Surio, 1963. Magma type and tectonic position of the Una-Una Island, Indonesia. Bull Volc, 26: 431-454.

Katili J A, Sudradjat A, 1984a. The devastating 1983 eruption of Colo volcano, Una-Una Island, central Sulawesi, Indonesia. Geol Jahrb, 75: 27-47.

Kusumadinata K, 1979. Data Dasar Gunungapi Indonesia. Bandung: Volc Surv Indonesia, 820 p.

Neumann van Padang M, 1951. Indonesia. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI, 1: 1-271.

Sudradjat A, 1977. . (pers. comm.).

Volcano Types


Tectonic Setting

Subduction zone
Continental crust (> 25 km)

Rock Types

Trachyandesite / Basaltic trachy-andesite
Trachyte / Trachyandesite


Within 5 km
Within 10 km
Within 30 km
Within 100 km

Affiliated Databases

Large Eruptions of Colo [Una Una] Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
Smithsonian Collections Search the Smithsonian's NMNH Department of Mineral Sciences collections database. Go to the "Search Rocks and Ores" tab and use the Volcano Name drop-down to find samples.