Transcript Slide 1
Chapter 8 Earth’s Core • 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