讲 环境地质学 Environmental Geology 主讲人:万新南教授 Prof wan xinnan 环境迪顶学 minoucntalocelogu ,率
环境地质学 Environmental Geology 主讲人：万新南教授 Prof. Wan xinnan
地球内部过程 Plate Tectonics Geologic Tectonics ° Earthquake Tsunamis海啸 and coastal Flooding 环境迪顶学 minoucntalocelogu ,率
地球内部过程 • Plate Tectonics • Geologic Tectonics • Earthquake • Tsunamis海啸 and Coastal Flooding
地球内部过程 Plate Tectonics Several centuries ago, observers looking at global maps noticed 代 the similarity in outline of the eastern coast of South America and the western coast of Africa. In 1855. Antonio Snider went so far as to publish a sketch showing how the two continents could fit together, jigsaw-puzzle fashion (1. Such reconstruction gave rise to the bold suggestion that perhaps these continents had once been part of the same landmass, which had later broken up. =312 环境迪顶学 minoucntalocelogu ,率
地球内部过程 • Plate Tectonics Several centuries ago, observers looking at global maps noticed the similarity in outline of the eastern coast of South America and the western coast of Africa. In 1855, Antonio Snider went so far as to publish a sketch showing how the two continents could fit together, jigsaw-puzzle fashion ①. Such reconstruction gave rise to the bold suggestion that perhaps these continents had once been part of the same landmass, which had later broken up
地球内部过程 Plate Tectonics This concept of continental drift had an especially vocal champion in Alfred Wegener(D, who began to publish his ideas in 1912 and continued to do so for more than two decades. several other prominent scientists found the dea plausible合理 However, most people scientists and nonscientists alike, had difficulty visualizing how something as massive as a continent could possible driftaround on a solid earth, or why it should do so 2. There were obvious physical objections异议 to solid continents plowing耕作 through solid ocean basins and no evidence of the expected resultant damage in crushed and shattered rock on continents or sea floor 3. The majority of reputable scientists at best, politely ignored i ea, or either scoffed嘲笑 at the id 环境迪顶学 minoucntalocelogu 真去率
地球内部过程 • Plate Tectonics This concept of continental drift had an especially vocal champion in Alfred Wegener①, who began to publish his ideas in 1912 and continued to do so for more than two decades. Several other prominent scientists found the idea plausible合理的. However, most people scientists and nonscientists alike, had difficulty visualizing how something as massive as a continent could possible "drift” around on a solid earth, or why it should do so②. There were obvious physical objections异议 to solid continents plowing耕作 through solid ocean basins, and no evidence of the expected resultant damage in crushed and shattered rock on continents or sea floor③. The majority of reputable scientists either scoffed嘲笑 at the idea, or, at best, politely ignored it
地球内部过程 Plate tectonics As it turns out其原因是,the supporting evidence was simply undiscovered or unrecognized at the time. Beginning in the 1960s, data of many different kinds began to accumulate that indicated that the continents have indeed moved Continental drift turned out产生tobe ust one aspect of a broader theory known as plate tectonics, which has evolved over the last two decades Tectonics is the study of large scale movement and deformation of the earths outer layers Plate tectonics relates such deformation to the existence and movement of rigid刚性 plates over a weak or partly molten layer in the earth's upper mantle 环境迪顶学 minoucntalocelogu 真去率
地球内部过程 • Plate Tectonics As it turns out其原因是, the supporting evidence was simply undiscovered or unrecognized at the time. Beginning in the 1960s, data of many different kinds began to accumulate that indicated that the continents have indeed moved. Continental drift turned out产生 to be just one aspect of a broader theory known as plate tectonics, which has evolved over the last two decades. Tectonics is the study of large scale movement and deformation of the earth’s outer layers. Plate tectonics relates such deformation to the existence and movement of rigid刚性 “plates”over a weak or partly molten layer in the earth’s upper mantle
地球内部过程 Plate Movements-Accumulating Evidence The Topography of the Sea Floor: If South America and Africa really have moved apart, one might expect to see some evidence of this between them some feature or features on the sea floor to indicate the continents passage. Topographic map of the floor of the Atlantic Ocean shows an obvious ridge running north- south about halfway不彻底、中途 between those continents 大陆间近南北向的明显洋脊. This mid- ocean ridge might be the seamsit from which the two continents moved apart. Similar ridges are found on the floors of other oceans, as seen in the same figure. In other places frequently along the margins of continents, there are trenches a r several kilometers deep. It remained for scientists studying the ages and magnetic properties of seafloor rocks as described below to demonstrate the significance of the ocean ridges to plate tectonics. The trenches too, can be explained by plate tectonics 环境迪顶学 minoucntalocelogu ,率
地球内部过程 • Plate Movements-Accumulating Evidence The Topography of the Sea Floor： If South America and Africa really have moved apart, one might expect to see some evidence of this between them, some feature or features on the sea floor to indicate the continents’ passage. A topographic map of the floor of the Atlantic Ocean shows an obvious ridge running north-south about halfway不彻底、中途 between those continents 大陆间近南北向的明显洋脊. This mid-ocean ridge might be the seam缝 from which the two continents moved apart. Similar ridges are found on the floors of other oceans, as seen in the same figure. In other places, frequently along the margins of continents, there are trenches沟堑several kilometers deep . It remained for scientists studying the ages and magnetic properties of seafloor rocks, as described below, to demonstrate the significance of the ocean ridges to plate tectonics. The trenches, too, can be explained by plate tectonics
地球内部过程 Plate Movements-Accumulating Evidence The Topography of the Sea Floor Juan de Fuca Plate Arabian Plate Pacific Plate hippie Plate ndian-Australian o Q African Pl American Antarctic Plate Direction of plate motion (sawteeth point toward Spreading ndge Transform fault 环境跑顶学 Cneinacntalgcelogu ,率
地球内部过程 • Plate Movements-Accumulating Evidence The Topography of the Sea Floor：
地球内部过程 Plate Tectonics Magnetismiii in Rocks--General Most iron-bearing minerals are at least weakly magnetic at surface temperatures Each magnetic mineral has a Curie居里 temperature, below which it remains magnetic, but above which it loses its magnetic properties. The Curie temperature varies from mineral to mineral, but it is always below the minerals melting temperature. A hot magma is therefore not magnetic, but as it cools and solidifies, and ferromagnesian 铁镁矿物 silicates and other iron-bearing minerals crystallize from it, those magnetic minerals tend to line up in the same direction. like tiny compass needles, they align themselves parallel to he lines of force of the earth's magnetic field, which run north-south, and they point to the magnetic north pole. They retain their internal magnetic orientation unless they are heated again. This is the basis for the study of paleomagnetism, fossil magnetism in rocks 环境迪顶学 minoucntalocelogu 真去率
地球内部过程 • Plate Tectonics Magnetism磁 in Rocks—General： Most iron-bearing minerals are at least weakly magnetic at surface temperatures. Each magnetic mineral has a Curie居里 temperature, below which it remains magnetic, but above which it loses its magnetic properties. The Curie temperature varies from mineral to mineral, but it is always below the mineral’s melting temperature. A hot magma is therefore not magnetic, but as it cools and solidifies, and ferromagnesian 铁镁矿物 silicates and other iron-bearing minerals crystallize from it, those magnetic minerals tend to line up in the same direction. Like tiny compass needles, they align themselves parallel to the lines of force of the earth’s magnetic field, which run north-south, and they point to the magnetic north pole. They retain their internal magnetic orientation unless they are heated again. This is the basis for the study of paleomagnetism, “fossil magnetism” in rocks
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
地球内部过程 Plate Tectonics The Topography of the Sea Floor: If South america and africa really have moved apart one might expect to see some evidence of this between them some feature or features on the sea floor to indicate the continents passage. A topographic map of the floor of the Atlantic Ocean shows an obvious ridge running north-south about ha lfway不彻底 中途 between those continents大陆间近南 北向的明显洋脊. This mid- ocean ridge might be the seams from which the two continents moved apart. Similar ridges are found on the floors of other oceans as seen in the same figure. In other places, frequently along the margins of continents, there are trenches沟堑 several kilometers deep. It remained for scientists studying the ages and magnetic properties of seafloor rocks as described below, to demonstrate the significance of the ocean ridges to plate tectonics. The trenches, too, can be explained by plate tectonics 环境迪顶学 minoucntalocelogu
地球内部过程 • Plate Tectonics The Topography of the Sea Floor： If South America and Africa really have moved apart, one might expect to see some evidence of this between them, some feature or features on the sea floor to indicate the continents’ passage. A topographic map of the floor of the Atlantic Ocean shows an obvious ridge running north-south about halfway不彻底、 中途 between those continents大陆间近南 北向的明显洋脊. This mid-ocean ridge might be the seam缝 from which the two continents moved apart. Similar ridges are found on the floors of other oceans, as seen in the same figure. In other places, frequently along the margins of continents, there are trenches沟堑 several kilometers deep . It remained for scientists studying the ages and magnetic properties of seafloor rocks, as described below, to demonstrate the significance of the ocean ridges to plate tectonics. The trenches, too, can be explained by plate tectonics
