ERS120H5 Chapter 2.7-2.12: ERS120 ch2.7-2.12
22 Jan 2018
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2. 10: special locations in the plate mosaic: triple junctions, geologists refer to a place where three plate boundaries intersect as a triple junction, hot spots, volcanoes are situated in the volcanic arcs that border trenches. They also lie along mid- ocean ridges, but ocean water hides most of them. The volcanoes pf volcanic arcs and mid ocean ridges are plate-boundary volcanoes. Not all volcanoes are plate-boundary volcanoes: 100 volcanoes exist in isolated points and are not a consequence of movement at a plate boundary. Imagine two cars speeding in the same direction down the highway. From the view of a tree along the side of the road, car a zips by at 100 km an hour, while car b moves at 80 km an hour. But relative to car b, car a moves at only 20 km an hour: geologists use two different frames of reference for describing plate velocity.
