Development of a Theory 14-2
Mid-Ocean Ridge Underwater mountain chain Valley in center Sediment thinner by ridge Rocks older farther away
Harry Hess US Naval Officer in WWII “Sea floor spreading” New sea floor at ridge
Seafloor Spreading Rift - Magma oozes out onto ocean floor Plates move away from each other Sea Floor Spreading - New crust forms
Seafloor Spreading North American Plate is moving away from European and African Plate
Normal Polarity Magnetized objects will point to the north
Reversed Polarity Magnetized objects point to the south
Magnetic Reversal Magnetic fields reverse direction 100,000’s of years to millions Magnetic minerals on ocean floor Mirrored alternating magnetic stripes on either side of ridge
More Evidence Magnetometer – tool Thermal energy Pillow lava Age and thickness of sediment
Magnetic Striping and Seafloor Spreading – You Tube