Today’s South Pacific earthquake is an example of Earth’s interacting spheres. The heat from within the Earth powered the magnitude 8.3 quake whose epicenter was 21 miles below the bottom of the Pacific Ocean. The shifting of Earth’s crust resulted in a tsunami killing 23 people on surrounding islands.

Here’s an excerpt from Discovery News about today’s quake.

Sept. 29, 2009 — A powerful earthquake with a magnitude of up to 8.3 struck off the South Pacific island nation of Samoa on Tuesday, triggering a tsunami as coastal residents fled to higher ground.

The Pacific Tsunami Warning Center said waves 1.57 meters (five feet) tall hit American Samoa, while 0.7 meter waves were recorded in Samoa.

The center had earlier issued a tsunami warning for a large swathe of the South Pacific including Fiji, New Zealand and Tonga after the U.S. Geological Survey reported a 7.9 magnitude quake.

The center later said an 8.3 magnitude quake had been recorded at a depth of 33 kilometers (21 miles). It was not immediately clear if this was the same quake and the USGS’s website did not provide exact details of its location.

“Sea level readings indicate a tsunami was generated,” said a statement from the Pacific Tsunami Warning Center.

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“It may have been destructive along coasts neat the earthquake epicenter and could alo be a threat to more distant coasts. Authorities should take appropriate action in response to this possibility.”