Why is earth geologically active

Why is Earth Geologically Active?
The cause of Earth being geologically active is that it retains heat in its interior. If we compare Earth to other planets, we find that Earth’s inner core goes through enormous radioactive decay of elements which produces heat thus causing Earth to be geologically active. Other planets are too cold at their interior to cause crustal movements, volcanoes and earthquakes. Badibanga asserts that the Earth took “ four billion years” to cool down, from outside to inwards, to the extent that the outer layers got solidified for the formation of oceans (97). The inner core of the Earth, which is made of Iron and Nickel, is still in the melted form which retains plenty of heat enough to keep active geology at the Earth’s crust.
The heat emitted as a result of radioactive decay or breaking apart of nuclei “ not recognized in Lord Kelvin’s time” (Garrison 67) flows inside out through conduction and convection causing the occurrence of volcanoes and earthquakes. This radioactive decay caused the melting of the mass of the Earth at the first place when most of the molten Iron sank down in the interior emitting copious energy.