August 4, 1928 Tsunami: Flores Sea, Indonesia
A tsunami caused by a volcano and a landslide began at Flores Sea, Indonesia on August 4, 1928. The water rose as high as 10 meters. Its effects were recorded at 2 places. It killed 226 people, counting the earthquake or eruption that caused it.
Where the waves reached
The source (white) and every runup with a place, colored by the water height recorded there. A ring is a runup NCEI marks doubtful.
- Under 1 m
- 1 to 3 m
- 3 to 10 m
- 10 to 30 m
- 30 m and more
- Height not recorded
Travel times
How long the first wave took to reach each part of the ocean, one line for each hour up to 24, estimated from the source and the depth of the sea.
The travel times are computed in your browser, which needs JavaScript.
- 1 to 4 hours
- 5 to 6 hours
- 7 to 14 hours
- 15 hours and more
Computed in your browser the way NOAA’s own travel time maps are: the wave travels at the square root of gravity times the depth, over NOAA’s ETOPO1 depths averaged to a 10 arc-minute grid. Checked against NOAA NCEI’s maps for 21 tsunamis over the first 24 hours, these lines fall within 10 minutes of NCEI’s at half the points compared and within 52 minutes at 9 in 10. They give when the first wave could arrive, not how high it is; bays, harbors and island chains finer than the grid can see it later. Not for use in a warning: see tsunami.gov.
The tsunami
- Date
- August 4, 1928
- Source
- Flores Sea, Indonesia
- Cause
- Volcano and landslide
- Volcano
- The eruption that caused it
- Maximum water height
- 10 m (32.8 ft)
- Runups recorded
- 2
- Tsunami intensity (Soloviev-Imamura)
- 3
- Tsunami magnitude (Iida)
- 3.3
- Waters
- Ocean
- How certain
- Definite tsunami
- Source location
- 8.320° S, 121.708° E
The toll
- Deaths
- 128; 226 with the earthquake or eruption that caused it
- Injuries
- 200 with the earthquake or eruption that caused it
- Damage
- Limited (under about $1 million); Moderate (about $1 to $5 million) with the earthquake or eruption that caused it
- Houses destroyed
- Some (about 51 to 100) with the earthquake or eruption that caused it
Where the literature gives no number, NCEI records a description on a scale of 1 to 4, printed here in its words. Damage is in millions of US dollars of the year of the event, not adjusted for inflation.
What the record says
NCEI’s account, from the sources it cites.
Conflicting reports on date of eruption and tsunami. Some papers (References #40, #79, #132, #1661, #2187, #12917) give date as August 4 or 7, 1927.
Reference #414:
August, on the night of the 4th-5th, 1928. There was a very strong eruption of the Rokatinda Volcano on Palu Island north of Flores Island. Three new craters were formed. A large amount of pumice, ash and bits of congealed lava were ejected. On falling, the eject set fire to the island's vegetation which was dry at that time of year. The entire island was showered with bits of pumice, but an especially thick layer of ash and pumice covered the southwestern quadrant of the island, including the settlements there. On the 5th and 6th, the ashes fell out as far as the Tenger Mountains on the east of Java. The volcano showed only slight activty after August 8.
In the eruption, 226 people died, 128 of them in the tsunami which occurred as the result of the displacement of the ground on the coast. Three waves 5-10 m high were observed both off Palu Island and on the nearest section of the coast of Flores Island. Twenty boats sank (reports appeared in the newspapers that the waves generated during the catastrophe on Palu island were supposedly observed as far as India, and that at Allegri near Allahabad, the sea supposedly retreated 2 km (1 mile), leaving many ships high and dry; there is absolutely no connection between the two above-mentioned phenomena).
On September 9 the eruption revived and ash was ejected and spread over the entire island. The activity of the volcano continued until September 25.
Every runup
Nearest the source first. Heights are above sea level at the time; a tide gauge reads half the wave’s full height.
| Where | Country | Km from source | Water height, m | Inland, m | Measured by | First wave, UTC | Deaths |
|---|---|---|---|---|---|---|---|
| Palu Island, Flores Sea | Indonesia | 0 | 10 | Eyewitness observation of water height | 128 | ||
| Flores Island | Indonesia | 80 | 10 | Eyewitness observation of water height |
More
Every tsunami in 1928The 1900sTsunamis of IndonesiaThe eruptionThis day in weather historyAlerts in force
Sources
Tsunami events and runups from NOAA’s National Centers for Environmental Information, Global Historical Hazard Database, cited as NCEI/WDS, doi:10.7289/V5PN93H7. Public domain. Read 2026-09-24. NCEI tsunami event 1607.