Chapter 8

Earth’s Core Lithosphere Lithosphere- solid outer crust of Earth – Rock and hot plastic-like upper mantle Three major parts or layers: – Earth’s core: Outer liquid portion Inner solid portion Composition believed to be iron and nickel

Earth’s Core (continued) 1,800 miles to outer core 1,300 miles to inner core Core is extremely hot – 8,000 F Used seismic waves to reveal composition Impossible to observe directly

Makes up most of Earth’s volume Composed of hot solid material – Silicon, oxygen, iron, aluminum, and magnesium – 1,800 miles think and extremely high pressure – Heat moves upward through mantle Forms convection cells

Extreme heat comes from: – Radioactive decay – Friction – Residual heat Upper mantle called the asthenosphere – Flows like thick syrup

Outer portion is composed of solid rock Thickness from 40 miles to 3 miles – 40 miles under mountains Continental crust- density 2.7 gm/cc – 3 miles under parts of the ocean Oceanic crust- density 3gm/cc Denser because of pressure of ocean

Oceanic crust made of basalt Earth floats on top of upper mantle – Like a cracker floating on soup Seven elements make up 99 percent of crust – Oxygen and silicon form 72 percent of the crust – Aluminum, iron, calcium, magnesium, sodium form the remainder Lower crust and upper mantle form the asthenosphere

Model developed using seismic waves Also studied inner composition of meteorites – Helps in understanding Earth’s interior Deepest penetration by drilling is 9 miles Deepest mine is slightly over 2 miles Model is constructed by inference

Inference- conclusion based on gathered evidence Can only infer because can’t travel there Many theories based on inference – Earth is so large – Much cannot be studied by direct observation Oceans Atmosphere

Earth’s Interior