want know Earth is difficult , beacuse you are not know the interior . outside is use hot form and exist on the inside. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ we won't use earth strength , this planet like moon . it is die word land. it strength help we make word and it protection earth . ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Continents have been created, mountains raised, only to later be lowered, hot magma has been pushed to the surface, as older rock is re-heated, turning back into magma, and so on. > < http://www.kidsgeo.com/geology-for- kids/index.php