Why do some islands sink?
Show answer & explanation
Answer: Volcanic islands cool and subside
Volcanic islands cool and subside ✓ — Correct! Volcanic islands form over hot spots where magma creates new land. The hot rock below heats and expands the oceanic crust, lifting the island. As the tectonic plate moves away from the hot spot, crust cools and contracts, causing the island to gradually sink. This creates atolls—ring reefs around sunken islands!
Ocean waves push islands deeper — Wrong. Waves erode island surfaces but cannot push entire islands downward into the mantle. Island sinking comes from thermal contraction—volcanic crust cools and becomes denser after moving away from hot spots.
Coral growth weighs islands down — Wrong. Coral reefs actually grow upward on sinking islands, forming atolls—they don't weigh islands down. Island subsidence happens because cooling volcanic crust contracts and becomes denser over millions of years.
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