8.1 moment magnitude
An earthquake happened, which triggered the tsunami.
An earthquake
The earthquake that caused the tsunami was on the same day, 29 September, 2009.
The earthquake triggered the tsunami
An earthquake.
It created the tsunami.
Act of nature.
It was triggered by an earthquake.
The tsunami was triggered by an earthquake.
You can't predict earthquakes
The word for "big" in Samoan is "tele."
In 2009, there was a big shake in Samoa called an earthquake. It caused the ground to move a lot and buildings to fall down. It made a big wave in the ocean that flooded some areas.