L02-EarthMaterials-3.ppt
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1、Chapter Three,Earth Materials and Processes,Zhao Hongjing Yangtze University,2,Earth Materials and Processes,Geologic cycle Minerals Rocks Water Wind and Ice,Zhao Hongjing Yangtze University,3,Fig 3.1,Geological cycle is composed of subcycles.,Zhao Hongjing Yangtze University,4,Geological cycle,Hydr
2、ologic cycle The movement of water from the oceans, to the atmosphere and back to the oceans, by way of precipitation, evaporation, stream runoff, and groundwater flow Tectonic cycle Driven by forces deep within the earth Deform the earths crust,producing external forms such as ocean basins, contine
3、nts and mountains Geochemical cycle The study of the distribution and migration of elements in earth processes. Rock cycle,Zhao Hongjing Yangtze University,5,Minerals,Minerals are a naturally occurring, solid, crystalline substance with chemical and physical properties such as density and hardness.
4、Minerals are the fundamental units from which most rocks are made. 2000 75% by weight of crust: O & Si 95% of crust: silicate Most important rock-forming minerals: quartz, feldspar, ferromagnesian,Zhao Hongjing Yangtze University,6,Rocks,Rocks are solid aggregates(集合体, 聚集体) of one or more minerals T
5、he rock cycle is the largest of the earth cycles Tectonic cycle energy Geochemical cycle material Hydrologic cycle water 3 rock families Igneous (火成) Metamorphic (变质) Sedimentary 沉积,镁铁硅酸盐,长英硅酸盐,辉石,橄榄石,黑云母,斜长石,花岗岩,Zhao Hongjing Yangtze University,7,The rock cycle,Zhao Hongjing Yangtze University,8,St
6、rength of rocks varies with composition, texture(结构,质地) and location, maybe quite different under different types and different amounts of stress.,Stress (应力) Force per unit area that develops within rocks to resist external forces compressive, tensile and shear Strain: (应变) deformation induced by a
7、 stress Elastic(弹性), plastic(塑性),Strength of Rocks,延展性,弹性(脆性),断裂强度,Zhao Hongjing Yangtze University,9,Strength of Rocks,Strength: The compressive, shear or tensile stress necessary to break a sample Safety Factor To ensure that a rock will perform as expected The rock is loaded only to a fraction of
8、 its assumed strength,Force per unit area that develops within rocks to resist external forces,挤压力,张力,剪切力,Zhao Hongjing Yangtze University,10,Strength of Rocks,Rock strength is highly variable. Many Factors: rock type texture chemical composition internal structures presence or absence of fluids Mos
9、t rocks already fractured by joints and faults. Fractured rocks are only as strong as whatever is holding the rock together (gravity or friction). fracture along planes of weakness fracture along bedding planes or along foliation planes,Zhao Hongjing Yangtze University,11,The strength of rocks is gr
10、eatly affected by the frequency and orientation of fractures, joints, and shear zones. When large structures are planned, shear zones and fracture system in rocks must be considered.,Zhao Hongjing Yangtze University,12,San Andreas Fault,Baldwin Hills Reservoir, failed in 1963, in southern California
11、, five lives $11 million, resulted from gradual movement along shear zones (faults) .,Zhao Hongjing Yangtze University,13,Some common rocks, shales for example, may share the same name but have different engineering properties depending on their deposition as well as lithification processes. Compact
12、ion shales are weak and can slide along bedding planes, slake (soften into mud when wet), and swell under certain conditions. Cemented shales, depending on the cementing material, can be very strong and suitable for most engineering enterprises.,Strength of Rocks,Zhao Hongjing Yangtze University,14,
13、Types of rocks,3 families: igneous, metamorphic, sedimentary Rock texture the size, shape and arrangement of grains along with fractures, shear zones, and faults, determines the strength and utility of rock. For intrusive igneous rock, more important in practical applications are the texture and nat
14、ure of fractures and related alteration zones.,Zhao Hongjing Yangtze University,15,Igneous rock,Igneous - formed by the cooling and crystallization of magma or lava Extrusive igneous rocks form at the Earths surface Considerable variety and composition Intrusive igneous rocks form beneath the Earths
15、 surface, such as granite. Strong, high compressive strength usually satisfactory for all types of engineering construction and operations,Types of rocks,Zhao Hongjing Yangtze University,16,Zhao Hongjing Yangtze University,16,Column joints,Zhao Hongjing Yangtze University,17,Zhao Hongjing Yangtze Un
16、iversity,17,FORMS OF VOLCANIC ROCKS,Extrusive (volcanic) igneous rocks form when molten rock erupts from Earths interior through a volcano or fissure and cools rapidly at the surface in form of Lava and hence it does not have any specific shape,Lava flows: On eruption lava simply flows on the surfac
17、e and on the basis of surface appearance, lava flows are described as blocky lava and ropy lava,Zhao Hongjing Yangtze University,18,Zhao Hongjing Yangtze University,18,Block Lava: is less mobile i.e. more viscous and has a rough and irregular surface. Vesicles(气疱) are few and irregular in shape,When
18、 cools down it result into angular, chunky(短而厚的) texture. This causes the lava to thicken and to break apart as the flow continues to move down slope. Such a texture is referred to as a-a, probably because of the pain inflicted on a person trying to walk across such a flow.,Zhao Hongjing Yangtze Uni
19、versity,19,Zhao Hongjing Yangtze University,19,Ropy Lava: is more mobile i.e. less viscous, it has a wrinkled(卷曲的) but smooth and shiny surface on cooling. Vesicles are more in number, small spherical in shape.,Zhao Hongjing Yangtze University,20,PYROCLASTS(火山碎屑) OR PYROCLASTIC:,Extrusive igneous ro
20、ck texture referred to as pyroclastic. This texture results from a very explosive eruption, which sends not only lava flying through the air, but also fragments of the volcano itself. All airborne volcanic fragments, referred to as pyroclasts,Zhao Hongjing Yangtze University,21,The rock fragments th
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