SCIE 1920U Chapter 5: 5 Terrestrial worlds
Document Summary
Earth is the most active and geologically active planet and next is venus. Size matters because most geological activity is driven by internal heat. All the terrestrial worlds were quite hot when they were young, because accretion of planetesimals converted gravitational potential energy into thermal energy. Decay of radioactive materials inside the terrestrial worlds provided additional heat (and still provides some heating today) Smaller worlds cool faster than bigger worlds. All the terrestrial worlds were hot enough to have had molten interiors when they were very young, allowing materials to separate by density in the process called differentiation. Core is the highest density material consisting primarily of metals such as nickel and iron to the central core. Mantle is rocky material of moderate density mostly made of silicon, oxygen, and other elements. Crust of the lowest density rock, such as granite and basalt.
