地球内部过程 Plate Tectonics always coincided with its presen ot Magnetic north however, has ng Figure 3.10 Bluewater wne ao pose Faery position. In the early 1900s farra firlf lla at Bat ine ped Bual scientists investigating the direction of magnetization of a sequence of volcanic rocks in France discovered eh gde wand some flows that appeared to be magnetized in the opposite direction 是5m from the rest: their magnetic minerals n y adteretsp: pointed south instead of north Confirmation of this discovery in many places around the world led to the suggestion in the late 1920s that the earth's magnetic field had “ flipped翻动," or reversed polarity; that is, that the north and south poles had switched转换 places. During the time those surprising rocks had crystallized, a compass needle would have pointed to the magnetic south pole, not north 环境迪顶学 minoucntalocelogu ,率地球内部过程 • Plate Tectonics Magnetic north, however, has not always coincided with its present position. In the early 1900s, scientists investigating the direction of magnetization of a sequence of volcanic rocks in France discovered some flows that appeared to be magnetized in the opposite direction from the rest: their magnetic minerals pointed south instead of north. Confirmation of this discovery in many places around the world led to the suggestion in the late 1920s that the earth’s magnetic field had “flipped翻动,” or reversed polarity; that is, that the north and south poles had switched转换 places. During the time those surprising rocks had crystallized, a compass needle would have pointed to the magnetic south pole, not north