Currents involve movement of ocean water masses, driven either by wind or by differences in temperature, salinity and density. The most important from a human perspective are the wind-driven surface currents that move water in the uppermost layer of the ocean.
Currents affect humans in several primary ways. Currents help shape the climate in the areas where we live, create the right conditions to support abundant ocean life in the areas where we fish, and change weather patterns through periodic events like El Nino/La Nina.
Ocean currents also cause upwelling in many areas like off in the inland parts of North America, where surface currents taking water away from the shore cause nutrient-rich water to well up from the ocean deeps. The abundance of nutrients in these areas forms fertile ground for kelp beds and marine fisheries, which in turn furnish food for humans. Alterations in current patterns like the El Nino/La Nina cycle affect humans as well by causing changes in local weather patterns in the years when they occur.
Igneous rocks form from magmas, and most magmas are associated with plate tectonics. Mafic (basaltic) and ultramafic magmas form along the divergent midoceanic ridges and are major components of new oceanic crust. More felsic magmas, such as andesites and rhyolites, are associated with the edges of continental crust at subduction zones along converging plate boundaries. Whether a magma is intermediate or felsic may depend on the relative amounts of oceanic crust and continental crust in the subduction zone that melt to form the magma. The great abundance of granitic intrusions in continental crust is thought to be related to the partial melting of the lower continental crust.
Intraplate igneous activity occurs in the interior of a single continental plate and is thought to be related to mantle plumes (such as the eruptions at Yellowstone National Park) or flood basalts. Intraplate activity is not associated with moving plate boundaries such as subduction zones.
During the Cenozoic era,mountain building in western North American was caused by tectonic activity.
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Answer:
The mountain ranges, the Appalachian mountains, the Rocky mountains, the Sierra Nevada.
Explanation:
