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Mr.hopkins
Science
| Mid-Ocean Ridge | A mountain range located on the seafloor in the middle of the ocean. |
| Seafloor Spreading | New oceanic crust forms at a mid-ocean ridge as old crust moves away |
| Normal Polarity | Earth’s magnetic field is like it is today; compass/magnet points north. |
| Reversed Polarity | Earth’s magnetic field flips; compass/magnet points south. |
| Magnetic Reversal | An event where Earth’s magnetic field reverses direction. |
| Shorter echo time | shallower water |
| Longer echo time | deeper water |
| shorter and longer echo times helped them discover | mid ocean ridges |
| magma rises because | it is less dense than the mantle |
| Pillow lava | underwater eruptions cool quickly |
| younger crust | at the ridge |
| older crust | farther away from the ridge |
| Which three types of evidence support seafloor spreading | magnetic stripes heat flow sediment thickness |
| What supports the idea that continents move with the seafloor? | new crust pushes continents outward like a conveyor belt |
| what evidence comes from drilling into the seafloor | more heat near mid ocean ridges |
| Magnetic stripes that match on both sides of the ridge show that— | new crust forms and spreads in both directions |
| which of the following is true about pillow lava | it forms underwater due to rapid cooling |
| Why is sediment thick far from the ridge? | older crust has had more time to collect sediment |
| Which evidence showed new crust forms at ridges and spreads outward? | magnetic stripes |
| Why is sediment thin near the ridge? | The crust is young and hasn't collected much sediment |
| What tool did scientists use to map the depth of the ocean floor? | Echo sounder |
| Why does underwater lava form “pillow lava”? | it cools rapidly in seawater |
| Why does magma rise at mid-ocean ridges? | it is less dense than the mantle |
| What did shorter echo-return times tell scientists? | The water is shallower |
| What did longer echo return times tell scientists? | The water is deeper |
| What instrument did scientists use to measure magnetic signals in ocean rocks? | magnetometer |
| What do magnetic minerals in basalt record when they cool? | the direction of earths magnetic field |
| What does increased heat flow near ridges show? | magma rises beneath the ridge |
| Why are abyssal plains so flat? | thick sediment smooths the seafloor |
| Which idea did seafloor spreading help explain? | Continental drift |
| Why do magnetic minerals line up when basalt cools? | they align with earths magnetic field |
| Why were scientists amazed by magnetic stripes? | they were mirror images on both sides of the ridge |
| What process forms new oceanic crust at a mid-ocean ridge? | seafloor spreading |
| What pattern did scientists find regarding crust age? | young crust near the ridge |
| Basalt contains | iron minerals that act like magnets |
Created by:
Leandro R