Earth's mass is divided into an inner core, outer core, mantle, and crust. The crust is outermost layer of the earth, 3–44 miles (5–70 km) thick and representing less than 1% of the earth's total volume.
The incompatible elements that end up in the continents are important because they include the major radioactive elements uranium, thorium, and potassium. These create heat, which makes the continental crust act like an electric blanket on top of the mantle.
The crust of the Earth is composed of a great variety of igneous, metamorphic, and sedimentary rocks. The crust is underlain by the mantle. The upper part of the mantle is composed mostly of peridotite, a rock denser than rocks common in the overlying crust.
The incompatible elements that end up in the continents are important because they include the major radioactive elements uranium, thorium, and potassium. These create heat, which makes the continental crust act like an electric blanket on top of the mantle.