4.1 E ARTH ’ S F ORMATION DAHS Mr. Sweet 1

O BJECTIVES Explain how most scientists explain the formation of our solar system. Describe Earth’s size and shape and the arrangement of its layers. List three sources of Earth’s internal heat. Describe Earth’s magnetic field. 2

N EBULAR H YPOTHESIS Most widely accepted model for solar system formation 4.6 billion years ago Cloud of gas and dust rotating in space Shrank due to pull of gravity, spinning faster Material collected at center and became hot. Hydrogen fusion began creating our sun. 3

P LANETISMALS Frictional, electromagnetic, and gravitational forces formed solid particles of ice and rock. Eventually formed planets and moons. 4

O BLATE S PHEROID A sphere that bulges in the center. Shape of Earth. Proof Measuring the weight of object at several places on Earth. 195 Newtons at Poles and 194 Newtons at equator. 5

E ARTH ’ S M EASUREMENTS Total surface area 510 million square km 55 continental USA’s 149 million square km is above sea level Ocean covers 361 million square km 29% dry, 71% wet 6

O RIGINAL E ARTH Looked like the moon Same material all the way thru Collisions created heat Heat melted iron and nickel Denser material moved to the center and lighter materials to the surface 7

L AYERS O F E ARTH Inner Core Outer Core Mantle Lithosphere Asthenosphere Crust 8

I NNER C ORE Solid iron and nickel 9

O UTER C ORE Surrounds the inner core Composed of liquid iron and nickel 10

M ANTLE Thickest of Earth’s layers Iron, Silicon, and magnesium Solid High pressure and temperatures cause it to behave as a liquid. 11

C RUST Thin, rigid layer Lighter rocks 12

O THERS Lithosphere Crust and uppermost mantle More rigid material Asthenosphere Slushlike layer of mantle Lithosphere floats on top Cause of plate tectonics 13

E ARTH ’ S H EAT Meteorite impacts Compression of Earth’s interior Decay of radioactive isotopes Slowly losing heat Differences in rock, crust thickness, and radioactive rock 14

T EMPERATURE A T D EPTH Above 70 feet temperature remains constant year round Below 70 feet temperature rises 1 o Celcius every 40 meters 15

M AGNETIC F IELD North Pole is the positive pole South Pole is the negative pole Tilted 11 O away from the poles Hypothesized that the fluid outer core creates the magnetic field Iron moves through and electric field creating another electric field 16

S ECTION R EVIEW 4.1 Page 74 Numbers 1, 2, 3, and 4 17