1820 Tsunami: Gold Coast, Congo
A tsunami caused by a magnitude 6.2 earthquake began at Gold Coast, Congo in 1820. Its effects were recorded at 2 places.
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
- 1820
- Source
- Gold Coast, Congo
- Cause
- Earthquake
- Earthquake
- Magnitude 6.2
- Runups recorded
- 2
- Waters
- Ocean
- How certain
- Questionable tsunami
- Source location
- 4.500° S, 11.600° E
The toll
- Deaths
- Many (about 101 to 1,000)
- Damage
- Limited (under about $1 million)
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.
1820. The earliest reported seismic sea-wave was associated with an earthquake about 1820 in Loango on the coast of Congo. ... Soon after the earthquake, or seaquake, that occurred at Cabenda, and which extended to some distance to the southward and northward of the port, a flight of locusts took place, that continued three days and three nights, so that the sea was literally covered with their drowned carcasses; ... the earthquake, which had preceded their flight only a few hours, drove in upon the shore from
the westward several tremendous seas, so as to cause
some of the vessels when in the trough of them to strike the ground in five and a half fathoms water. Many of the natives, both here [Cabenda], and at Malemba, were drowned upon the beach, in consequence of it being so very narrow, and the cliffs which bound it so extremely precipitous, that they could not escape the overwhelming waves which came suddenly upon them. To this calamity, was added, the destruction of many canoes, by this sudden inundation of the sea ... . This is quite clearly the description of a relatively large seismic sea-wave associated with an earthquake which was felt over a very large area of West Africa. (reference #1214)
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 |
|---|---|---|---|---|---|---|---|
| Malembo | Angola | 112 | Eyewitness observation of water height | ||||
| Cabinda | Angola | 134 | Eyewitness observation of water height |
More
Every tsunami in 1820The 1800sTsunamis of CongoThe earthquakeAlerts 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 3561.