Thermal expansion: The increase in volume of a material as it gets warmer. For example, water expands as it is heated, causing each drop of water to increase in size. In the ocean, thermal expansion is one cause of rising sea level.
Thermal expansion: The increase in volume of a material as it gets warmer. For example, water expands as it is heated, causing each drop of water to increase in size. In the ocean, thermal expansion is one cause of rising sea level.