Convection currents produce the heat in the earth’s interior.

Convection currents in Earth's mantle are caused by the rise of hot material rising towards the crust, becoming cooler and sinking back down. This process occurs repeatedly, causing the currents to constantly flow. The movement of the currents plays a factor in the movement of the mantle

Convection currents in the magma drive plate tectonics. Heat generated from the radioactive decay of elements deep in the interior of the Earth creates magma (molten rock) in the aesthenosphere. It helps transfer heat from Earth's core, where magma is created through radioactive decay, to the mantle.

It will take annabelle 4 hours to complete her homework. if it took her 3 hours to finish 75%, then it probably took her 1 hour for every 25% she finished. if she finished 75%, she has 25% left to be done or 100% complete. 25% = 1 hour. so 3 hours + 1 hour = 4 hours or 100% complete