Conduction is the transfer of thermal energy through direct contact between two substances. On Earth, conduction occurs in the solid layers of the planet, including the crust, mantle, and inner core.

The crust is the outermost layer of the Earth and is composed primarily of solid rock. Heat is transferred through the crust by conduction from the warmer mantle below to the cooler surface. The mantle is the thickest layer of the Earth and is also composed primarily of solid rock. Heat is transferred through the mantle by conduction from the hotter inner core to the cooler crust. The inner core is the innermost layer of the Earth and is composed primarily of solid iron. Heat is transferred from the inner core to the mantle by conduction.

Conduction also occurs in the Earth's oceans and atmosphere, but to a lesser extent than in the solid layers. In the oceans, heat is transferred by conduction from the warmer surface waters to the cooler deep waters. In the atmosphere, heat is transferred by conduction from the warmer ground surface to the cooler air above.