❓ why
Why do some tsunamis arrive as a sudden drawdown of the sea before the main wave?
ScienceTsunamis
Quick Answer
The trough of the tsunami can reach the coast first, temporarily pulling water away from shore.
The Full Story
A tsunami is not a single crest but a long wave train with both peaks and troughs. If the trough reaches the shoreline first, the sea may suddenly withdraw, exposing the seafloor before the following crest arrives. This retreat is often one of the most dangerous warning signs because people may be tempted to walk out onto the exposed area. Historical tsunami accounts from the Indian Ocean and Pacific describe this alarming drawdown.
Key Facts
1.A tsunami includes troughs as well as crests
2.Sea withdrawal can be a warning sign
3.The Indian Ocean tsunami produced dramatic drawdown in some places
YouTube Angle
Suggested video title for this topic:
"Why does the ocean sometimes run away before a tsunami hits?"