PLATE TECTONICS Part 2

Geographic Puzzle _______________ noted that Africa and South America appear to fit together neatly, like the pieces of a jigsaw puzzle _______________ noted that Africa and South America appear to fit together neatly, like the pieces of a jigsaw puzzle He proposed that the continents had been joined and had since drifted apart He proposed that the continents had been joined and had since drifted apart

Pangaea Wegener suggested that 225 mya all of the land masses were connected in a supercontinent called ______________, a Greek word meaning ‘______ ________’ Wegener suggested that 225 mya all of the land masses were connected in a supercontinent called ______________, a Greek word meaning ‘______ ________’ _______________, Greek for ‘______ ________’, was the name given to the resulting world ocean. _______________, Greek for ‘______ ________’, was the name given to the resulting world ocean.

Continental Drift Wegener proposed that the continents floated somewhat like icebergs in water… Wegener proposed that the continents floated somewhat like icebergs in water… …and that the continents had drifted apart …and that the continents had drifted apart He did not know what caused the continents to drift apart He did not know what caused the continents to drift apart His theories were not widely accepted His theories were not widely accepted

Wegener’s Evidence Fossil remains in continuous bands across continents Fossil remains in continuous bands across continents ______________ - a land reptile from the Triassic period and ______________ - a land reptile from the Triassic period and ______________ – a tropical fern ______________ – a tropical fern mountain ranges and _________ deposits run uninterrupted across both continents mountain ranges and _________ deposits run uninterrupted across both continents

Wegener’s matching of mountain ranges on different continents

PLATE TECTONICS TELLS US The lithosphere consists of numerous differently sized pieces called plates The lithosphere consists of numerous differently sized pieces called plates

Science and the War During WWII, Harry Hess was a captain in the Navy on a transport ship. During WWII, Harry Hess was a captain in the Navy on a transport ship. His vessel was equipped with an echo sounder (___________) which Hess used to map the ocean floor to aid the war effort His vessel was equipped with an echo sounder (___________) which Hess used to map the ocean floor to aid the war effort In the postwar period the Atlantic was extensively mapped and the _____________________ was discovered In the postwar period the Atlantic was extensively mapped and the _____________________ was discovered

Mid-Atlantic Ridge a giant undersea mountain range extending north to south in the center of the Atlantic Ocean a giant undersea mountain range extending north to south in the center of the Atlantic Ocean Ocean sediments were discovered to be youngest near the __________ and oldest near the ______________ ________. Ocean sediments were discovered to be youngest near the __________ and oldest near the ______________ ________. MAR is evidence of sea-floor spreading MAR is evidence of sea-floor spreading

Ocean Floor Has Mountain Ranges larger than those found on the surface

Sea-Floor Spreading Hess’s theory that new ocean crust is formed at mid-ocean ridges and destroyed at ____________ ________. Hess’s theory that new ocean crust is formed at mid-ocean ridges and destroyed at ____________ ________.

__________________ The earth’s magnetic field has reversed many times over geologic time. The earth’s magnetic field has reversed many times over geologic time. A record of these reversals is fixed in rock as new ocean crust is formed at the mid ocean rift A record of these reversals is fixed in rock as new ocean crust is formed at the mid ocean rift Magnetic Stripes

In the late 1950’s scientists began studying the ocean floor with _____________________ invented in WW II In the late 1950’s scientists began studying the ocean floor with _____________________ invented in WW II Their purpose was to study compass distortions caused by ____________ on the seafloor Their purpose was to study compass distortions caused by ____________ on the seafloor

What did they find? What did they find? A series of ___________ along the ocean floor A series of ___________ along the ocean floor One stripe adds to the Earth’s magnetic field causing a __________ signal on the magnetometer One stripe adds to the Earth’s magnetic field causing a __________ signal on the magnetometer The stripes adjacent to this stripe subtracts from Earth’s magnetic field, causing a __________ signal on the magnetometer The stripes adjacent to this stripe subtracts from Earth’s magnetic field, causing a __________ signal on the magnetometer These stripes were found to be symmetrical around the ____________ of the mid-ocean ridge These stripes were found to be symmetrical around the ____________ of the mid-ocean ridge

The cause of the reversals is unknown, but is thought to be associated with changes in the motion of the magnetic material of Earth’s ________ _______

In 1963 an interpretation of these stripes was developed In 1963 an interpretation of these stripes was developed Earth’s magnetic field reverses at regular intervals of a few hundred thousand years___________ _____________ ________. Earth’s magnetic field reverses at regular intervals of a few hundred thousand years___________ _____________ ________. During a reversal, a compass points south, also causing the ____________ minerals in newly forming rocks to point south During a reversal, a compass points south, also causing the ____________ minerals in newly forming rocks to point south This evidence helped to solidify the theory of plate tectonics. This evidence helped to solidify the theory of plate tectonics.

Questions: Answer on separate paper and turn in. Where are the youngest rocks in the ocean crust? The oldest? Why? Where are the youngest rocks in the ocean crust? The oldest? Why? What biological evidence supports plate tectonics theory? What biological evidence supports plate tectonics theory? The continents are very old, the seabeds very young. Why is that? The continents are very old, the seabeds very young. Why is that? What evidence finally "clinched" the idea of plate tectonics? What evidence finally "clinched" the idea of plate tectonics?