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8.1 Note-taking Guide B
1. Denser materials such as iron and nickel sank toward the center. Less dense materials
moved toward the surface. Other materials settled between those two areas.
2. Gravity and impacts helped produce intense heat. The impacts also added materials
and increased Earth’s mass.
3. The energy moves slower through less dense materials and liquids. The energy moves
faster through more dense materials or solids.
4. Inner core: under great pressure; densest layer; remains hot, solid ball of materials;
outer core: under lower pressure than inner core; remains liquid, dense metals; still
extremely hot; surrounds inner core; about 2300 km; mantle: thickest layer; about 2900
km; above the outer core; upper part is cooler and more rigid; lower part is hot and soft; a
molten layer in the upper mantles called the asthenosphere; crust: home to all life on
Earth; thin, like an egg shell; includes all continents; islands, and ocean floor; thinnest
under oceans, thickest under mountains.
5. Earth’s crust and the very top of the mantle.
6. A layer of hotter, softer rock in the upper mantle; sits just below the lithosphere.
7. Tectonic plates are large and small slabs of rock that fit together to form the
lithosphere. Most large tectonic plates include both continental and oceanic crust.
Continents are the part of the plate that is visible above the water. Under the water, the
oceanic crust forms the sea floor of the world’s oceans and seas.