Pacific tsunami warning recedes; Tonga covered by ash cloud

The tsunami threat throughout the Pacific from a huge underwater volcanic eruption has begun to recede, though the massive ash cloud covering Tonga is preventing surveillance flights from New Zealand to assess the extent of damage.

What is a tsunami and what causes them?

All coastlines around the world are vulnerable to tsunamis, so it's important to know your community's hazard and evacuation plans in case they're needed.