The shores are covered with coral; earthquakes and tidal waves are frequent, the latter not taking the form of bores, but of a sudden steady rise and equally sudden fall in the level of the sea; the climate is rather tropical than temperate, but sickness is almost unknown among the residents.
On the 16th of March 1889 the heavy tidal waves created havoc in the harbour of Apia.
Apparent proof has been obtained that the shocks occurring in the Pacific districts originate at the bottom of the sea the Tuscarora Deep is supposed to be the centre of seismic activity and they are accompanied in most cases by tidal waves.
They are connected with the ocean by narrow straits, the salinity of the water contained in them differs in a marked degree from that of the ocean, and the tidal waves are of small amplitude.
When the earthquake occurs on the coast, or beneath the sea in its vicinity, tidal waves are sometimes formed, which cause even greater damage than the earthquake itself.