What causes waves?

Dateline article| David Murphy|

Waves have several causes. Probably the most common is wind. But a change in density within the water (in other words, one area of water that's more dense and heavier moving next to an area of less dense, lighter water) can get a wave going. Other causes include a small disturbance within or below the water (like the movement of a ship, submarine, or whale), earthquakes (which are the main causes of tsunamis) and the gravitational pull of the sun and moon.

---D.M.

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