CK12 Earth Science
Figure6.12: AmodernmapoftheeasternPacificandAtlanticOceans. Darkerblueindicates deeper seas. A mid-ocean ridge can be seen runni ...
they are now, geologists say the polarity is normal. When they are in the opposite position, they say that the polarity is rever ...
find that oldest seafloor is less than 180 million years old while the oldest continental crust is around 4 billion years old. T ...
It is the creation and destruction of oceanic crust, then, that is the mechanism for Wegener’s drifting continents. Rather than ...
Further Reading / Supplemental Links http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_seafloorspreading. html Vocabulary ...
Explain how mantle convection moves lithospheric plates. Describethethreetypesofplateboundariesandwhethertheyarepronetoearthqua ...
Figure 6.15: The bold pink swatch outlines the volcanoes and active earthquake areas found around the Pacific Ocean basin, which ...
were then termedplate tectonics. A single plate can be made of all oceanic lithosphere or all continental lithosphere, but nearl ...
Figure 6.17: The lithospheric plates and their names. The arrows show whether the plates are moving apart, moving together, or s ...
Figure 6.18: Convection in the mantle is the driving force of plate tectonics. Hot material rises at mid-ocean ridges and sinks ...
Beneath the moving crust is the laterally moving top limb of the mantle convection cells. Each convection cell is moving seafloo ...
Figure 6.19: The Leif the Lucky Bridge straddles the Mid-Atlantic ridge separating the North American and Eurasian plates on Ice ...
Figure 6.20: The Arabian, Indian, and African plates are rifting apart, forming the Great Rift Valley in Africa. The Dead Sea fi ...
Figure6.22: ThissatelliteimageshowsthetrenchliningthewesternmarginofSouthAmerica where the Nazca plate is subducting beneath the ...
The volcanoes of northeastern California—Lassen Peak, Mount Shasta, and Medicine Lake volcano—along with the rest of the Cascade ...
roughly 200 million years ago (Figure6.24). Similar batholiths are likely forming beneath the Andes and Cascades today. Figure 6 ...
volcanic islands are set off from the mainland in an arc shape as seen in this satellite image of Japan (Figure6.26). Figure 6.2 ...
Figure 6.27: When two plates of continental crust collide, the material pushes upward form- ing a high mountain range. The remna ...
the Pacific and North American plates grind past each other, sometimes with disastrous consequences. Figure 6.29: At the San And ...
Earth’s Changing Surface Geologists now know that Wegener was right when he said that the continents had once been joined into t ...
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