地球的英文介绍

1、In troductio nThis task is about the structure of the earth, seismic waves, plate tectonics, Australia and people how living near plate boundaries affects. I will clean writing about those.1.Structure of the Earth1.1(i ntroduct ion about the layers of the Earth)The Layers of the Earth are the crust,

2、 the mantle, the outer core, and the inner core.There are also sect ions of the man tle, which are the lithosphere, the asthe no sphere, and the lower man tle.(Crust)The upper crust for granite layer (magmatic rocks), mainly by silicon-aluminum oxide form; the lower for basalt layer (magmatic rocks)

3、, mainly by silicon magnesium oxide-form. The theory is that through the earths crust in temperature and pressure in crease with depth, every 100 meters deep temperature 1C . The drilli ng resultsshow that in rece nt years, were three kilometers or more in every 100 meters deep temperature of 2.5 C

4、, 11 kilometers to the depths of up to 200 C temperature.(Inner Core) An extremely hot, solid sphere of mostly iron and nickel at the center of the earth. It is 3200 to 3960 miles (5150 to 6378 km) below the surface and about 750 miles (1200 km) in diameter.(Outer Core)The outer core is the only liq

5、uid layer of the earth-a sea mostly iron and ni ckel (2890 to 5150 km) below the surface and about 1400 miles (2300km) thick.(Ma ntle)Subdivided into two regi ons, upper and lower, this dense layer made of hot, semisolid rock is located directly below the crust and is about 1800miles(2900 km) thick.

6、(Mantle- Lithosphere )Made up of the crust and a tiny bit of the upper mantle, this layer is divided into several constantly (very slowly) moving plates of solid rock that hold the continents and ocea ns(Ma ntle- Asthe no sphere )The plates of the lithosphere move (or float) on this hot, malleable s

7、emiliquid zone in the upper man tle, directly undern eath the lithosphere.1.2 (Explai n their in flue nee on the Earth)(Molten)Eve n if the causes of the phe nomenon rema in still difficult to determ ine, scie ntists agree in saying that the planets magnetic pole is in continual movement.Itsdrift is

8、most likely caused by the Earths always movi ng molte n, in flue need by the fluctuatio ns in solar radiati on.Notcorresp onding to the positi on of the geographicpole, the mag netic pole moves at a rate of about 40 kilometers a year.Its drift across the North Pole is, each and every year, closely m

9、onitored by the Geologic Survey of Can ada.(Partially Molte n)The microstructure of partially molten rocks plays a key role in determining their physical properties. The area fractio n of in tergra nu lar con tact, con tiguity, gover ns the establishme nt of a skeletal framework of solid grains and

10、con trols the effective elastic moduli of the aggregate. This work presents a theoretical calculation of steady state grain shape, con tiguity, effective elastic moduli, and S and P wave velocities for a partially molten aggregate containing an approximate melt volume fractio n of 0.09. The steady s

11、tate microstructure is con trolled by surface tension gradie nts aris ing from in teractio n among adjace nt grains in a close-packed aggregate. The ratio of viscosity between the grains and the melt, as well as the capillary nu mber, stron gly in flue nce the con tiguity(Solid)The earth formed appr

12、oximately 4.6 billi on years ago from a n ebular cloud of dust and gas that surro un ded the sun. As the gas cooled, more solids formed. The dusty material accreted to the n ebular midpla ne where it formed progressively larger clumps. Eventually, bodies of several kilometers in diameter formed; the

13、se are known as pla netesimals. The largest pla netesimals grew fastest, at the expe nse of the smaller ones. This process continued until an earth-sized planet had formed.Early in its formation, the earth must have been completely molten. The main source of heat at that time was probably the decay

14、of n aturally-occurri ng radioactive eleme nts. As the earth cooled, den sity differe nces betwee n the formi ng min erals caused the in terior to become differe ntiated in to three concen tric zon es: the crust, man tle and core. The crust exte nds dow nward from the surface to an average depthof 3

15、5 km where the man tie begi ns. The man tie exte nds dow n to a depth of 2900 km where the core beg ins. The core exte nds dow n to the cen ter of the earth, a depth of about 6400 km from the surface.1.3 (Explai n differe nces betwee n compositi onal and mecha ni cal boun daries)COMPOSITIONAL LAYERS

16、MECKANECAL LAYERS(Compositi on al layers )ThisThere are two major types of crust: crust that makes up the ocea n floors and crust that makes up the continen ts. Ocea nic crust is composed en tirely of basalt extruded at mid-ocean ridges, resulting in a thin ( 5 km), relatively dense crust (3.0 g/cm

17、3). Continental crust, on the other hand, is made primarily of less dense rock such as gran ite (2.7 g/cm 3). It is much thicker tha n ocea nic crust, ra nging from 15 to 70 km. At the base of the crust is the Moho, below which is the man tle, which contains rocks made of a den ser material called p

18、eridotite (3.4 g/cm3). compositional change is predicted by the behavior of seismic waves and it is con firmed in the few samples of rocks from the mantle that we do have.At the core-ma ntle boun dary, compositi on cha nges aga in. Seismic waves suggest this material is of a very high density (10-13

19、 g/cm3), which can only correspond to acompositi on of metals rather tha n rock. The prese nee of a magn etic field around the earth also in dicates a molte n metallic core. Un like the crust and the man tle, we don have any samples of the core to look at, and thus there is some controversy about it

20、s exact composition. Most scientists, however, believe that iron is the main con stitue nt.(Mechanical layers )The compositi onal divisio ns of the earth were un derstood decades before the developme nt of the theory of plate tect onics - the idea that the earth surface con sists of large plates tha

21、t move .By the 1970s, however, geologists bega n to realize that the plates had to be thicker tha n just the crust, or they would break apart as they moved. In fact, plates con sist of the crust act ing together with the uppermost part of the mantle; this rigid layer is called the lithosphere and it

22、 ranges in thickness from about 10 to 200 km. Rigid lithospheric plates float on a partially molte n layer called the aesthe no sphere that flows like a very viscous fluid, like Silly?Putty . It is importa nt to note that although the asthe no sphere can flow, it is not a liquid, and thus both S- an

23、d P-waves can travel through it. At a depth of 660 km, pressure becomes so great that the man tle can no Ion ger flow, and this solid part of the man tle is called the mesosphere. The lithospheric man tle, asthe no sphere, and mesosphere all share the same composition (that of peridotite), but their

24、mecha ni cal properties are sig nifica ntly differe nt. Geologists ofte n refer to the asthe no sphere as the jelly in betwee n two pieces of bread: the lithosphere and mesosphere.The core is also subdivided into an inner and outer core. The outer core is liquid molten metal while the inner core is

25、solid. The distinction between the inner and outer core was made in 1936 by Inge Lehma nn, a Danish seismologist, after improvements in seismographs in the 1920s made it possible to see ” previously un detectable seismic waves within the P-wave shadow zone. These fai nt waves indicated that they had

26、 been refracted again within the core when they hit the boun dary betwee n the inner and outer core.2. Seismic waves2.1 (What are seismic waves?)Seismic waves travel faster in the ,mantle than they do in the crust, because it is composed of denser material.Occurs in the source and in the surface of

27、the earth and the spread of in ternal elastic wave called seismic waves. Seismic waves gen erated by earthquakes is also the elastic wave.2.2 (What type of seismic waves do we have?)(body - P Waves )Primary waves (or P waves) are the fastest moving waves, traveling at 1 to 5 miles per sec ond (1.6 t

28、o 8 kilometers per sec on d). They can pass through solids, liquids and gases easily. As they travel through rock, the waves move tiny rock particles back and forth - pushi ng them apart and the n back together -in line with the directi on the wave is traveli ng. These waves typically arrive at the

29、surface as an abrupt thud.(body - S Waves)Secondary waves (also called shear waves, or S waves) are another type of body wave. They move a little more slowly tha n P waves, and can only pass through solids. As S waves move, they displace rock particles outward, pushing them perpendicular to the path

30、 of the waves. This results in the first period of rolling associated with earthquakes. Un like P waves, S waves dont move straight through the earth They only travel through solid material, and so are stopped at the liquid layer in the Earths core.(surface- L Waves )Un like body waves, surface wave

31、s (also known as long waves, or simply L waves) move along the surface of the Earth. Surface waves are to blame for most of an earthquakes earn age. They move up and dow n the surface of the Earth, rock ing the foun dati ons of man-made structures. Surface waves are the slowest movi ng of all waves,

32、 which means they arrive the last. So the most intense shaking usually comes at the end of an earthquake.2.3 (How do they move through the earths surface?)P waves-compressi on-ca n travel solidsS waves-ripple waves-ca nt thought the solidsL waves-Rayleigh waves-gro und roll-travel ur ripple-love wav

33、es-Arular shori ng2.4(Expla in how an alys ing these waves scie ntists are able to determ ine what is in side the Earth )Kno wledge of the Earths in terior is based on the reacti ons of seismic waves from earthquakes to the den sity and state of materials that they encoun ter. Seismic waves travel a

34、t differi ng speeds through differe nt materials (and also, at differe nt speeds through material of differe nt states, i.e., liquid or solid). Because we know the size of the Earth, by measuri ng how long it takes to pick up on seismic activity on opposite sides of the Earth, we can gauge about how

35、 much of the Earth is solid, liquid, made of a certa in materia.2.5(What is the Moho?)The Mohorovicic disc ontin uity, usually referred to as the Moho, is the boun dary betwee n the Earths crust and the man tle. The Moho serves to separate both ocea nic crust and continen tal crust from un derly ing

36、 man tle. The Moho mostly lies en tirely within the lithosphere; on ly ben eath mid-ocea n ridges does the Moho also defi ne the lithosphere-asthe no sphere boun dary. The Mohorovicic disc ontin uity was first ide ntified in 1909 by An drija Mohorovicic, a Croatia n seismologist, whe n he observed t

37、he abrupt in crease in the velocity of earthquake waves (specifically P- waves) at this point.2.6(Expla in how it was foun d?)1909 A.Mohorovicic defi ned the frist magor bamdary betwee n the crust and man tle. That is a depth where seismic waves cha nges in chemical where is a cha nge in chemical co

38、mpositi on.3. plate tectonics3.1(What are tect on ic plates?)Tectonic plates are large plates of rock that make up the foundation of the Earths crust and the shape of the continents. The tectonic plates comprise the bottom of the crust and the top of the Earths mantle.3.2(What the major plates on a

39、world map?)First the global lithosphere is divided into six parts, n amely the Pacific plate, the Eurasia n plate, the In dia n Ocea n plate, plate, America, Africa and An tarctica plate tect onic plates.3.3(Expla in the Wage ners theory con ti nen tal drift. What was the evide nee that supported hi

40、s theory? Why was it rejected at frist?)As evide nee, he no ted, as had others before him, of the geographic correlati on in coastl ine perimeters of South America and Africa. This was the feature that led Wage ner to inv estigate for other evide nces. His inv estigati ons revealed that mountain ran

41、ges in South America and Africa, and strata and composition of coal fields in Europe and North America matched or lined up. Additi on ally, matchi ng reptilian fossils were found on either side of the ocean, indicating that the continents were once joined together.Because he had no physical mecha ni

42、sm to expla in how his isla nds of rock could go freely saili ng about where they wan ted to through the solid rock of the ocea n floor. That was how his theory was see n at the time.3.4(What is the mai n differe nee betwee n the Wage ners theory of continen tal drift and Theory of plate tect oni cs

43、? )Continen tal drift theory was proposed before the discovery of the mid-ocea nic ridges, whe n it was hypothesized that the continents were actually plow ing through the ocea ns. This theory was an attempt to explai n the com mon ality of fossils on opposite sides of the Atlantic Ocean, and the ob

44、servation on maps of the Earth that the North America n and South America n continents appeared to have bee n pulled apart fromEurope and Africa. With the discovery of the mid-ocea nic ridges, where new crustal plate is being created, and subduct ion zon es, where plates are being destroyed, plate t

45、ecto nic theory was born; that the crust of the earth is divided in to many segme nts that are in con sta nt motio n, that the ocea nic crust is con sta ntly being recycled-all drive n by heat from the Earths in terior.3.5(Describe the evide nee that Theory of the plate tect oni cs.)To expla in the phe nomenon of con ti nen tal drift developed a geological theory. The the