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Evidence for Plate Tectonics (conclusion)

Science- Earth's Crust Grade 7 curriculum

Rebecca Arnold

on 20 April 2010

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Transcript of Evidence for Plate Tectonics (conclusion)

Conclusion to Plate Tectonics Sonar Sonar stands for Sound Navigation and Ranging. This technology is used in nature by bats to navigate around objects in the dark. Sonar works by sending out a sound and then recording the time that the sounds takes to bounce back. For example, scientists can bounce a sound off the ocean floor and measure the time that it takes to bounce back. Since they know how fast the sound travels, they can calculate the distance to the bottom of the ocean.
sea floor was not flat
Sonar proved this meaning that plate tectonic theory
and continental drift theory could be true
But what was causing these mountains to form? Magnetometers magnetometers are electronic instruments that can
detect the direction and strenght of a magnetic field
Used in WWII to locate subs
scientists found that the magnetometers recorded a magnetic field that pointed north most of the time
ships were noticing that the magnetometers would pull south at certain points over the ocean
pattern- parallel with the Mid-Atlantic Ridge
Magma contains iron-bearing minerals- line themselves up with Earth's magnetic field.
lines formed different times
lined up with the ridges so it meant the the sea floor was spreading Deep Sea Drilling and Radioactive Dating Scientists proved the theory of sea floor spreading when they were able to bring up samples of rock for testing.
Testing of the rock samples showed that younger rocks was closer to the Mid-Atlantic Ridge and the older rock was closer to the continents Submersibles Most of the volcanic activity where rock surfaces are pulling apart happens on the sea floor, where it cannot be seen. Scientists can travel in submersibles to the bottom of the Atlantic Ocean to see lava pouring out of the underwater volcanoes that form a line from north to south in the middle of the ocean. This is the same area where shallow earthquakes take place as rock pulls apart. http://www.google.com/imgres?imgurl=http://woodshole.er.usgs.gov/operations/sfmapping/images/sonar2.jpg&imgrefurl=http://woodshole.er.usgs.gov/operations/sfmapping/sonar.htm&usg=__7zull1R3Hi8CpePY23QXFVHqmoE=&h=283&w=460&sz=30&hl=en&start=3&itbs=1&tbnid=2yEDQBSUlgVb8M:&tbnh=79&tbnw=128&prev=/images%3Fq%3Dsonar%26hl%3Den%26gbv%3D2%26tbs%3Disch:1
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