What causes convection currents inside earth?

Study about the air moving pattern. when they are difference in pressure the air moves from high-pressure area to low pressure area same way the lithosphere get heat from its under layer that is molten metal called asthenosphere

In Earth's mantle, large amounts of heat are transferred byconvection currents, as shown in Figure 10. Heat from the core and the mantle itself causes convection currents in the mantle. Figure 10Mantle Convection Most geologists think that convection currentsrise and sink through the mantle.