Thousands of dead sardine fish landed along the Laura Kati River in Chile recently.

Phenomenon reports say huge numbers of the ocean fish swam into the river, reducing the water's oxygen level.

Tests on the sardine remains suggest the mass death resulted from a natural phenomenon related to the supply of oxygen in waterways.

A phenomenon is an observable fact or event, but people use the word most often when such an event is rare, powerful or of mysterious, cause now you know what phenomenon means.