地球的英文介紹

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

2、crust, the man tle, the outer core, and the inner core.There are also sect ions of the man tle, which are the lithos phere, the asthe nosp here, and the lower man tle.(Crust)The upper crust for gran ite layer (magmatic rocks), mai niy by silico n-alumi num oxide form; the lower for basalt layer (mag

3、matic rocks), main ly by silic on magn esium oxide-form. The theory is that through the earth's crust in temp erature and p ressurein crease with dep th, every 100 meters dee p temp erature 1C . The drilli ng results show that in rece nt years, were three kilometers or more in every 100 meters d

4、ee ptemp erature of 2.5 °C , 11 kilometers to the dep ths of up to 200°C temp erature.(Inner Core)An extremely hot, solid sp here of mostly iron and n ickel at the cen ter of the earth. It is 3200 to 3960 miles (5150 to 6378 km) below the surface and about 750 miles (1200 km) in diameter.(

5、Outer Core)The outer core is the only liquid 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 cru

6、st and is about 1800miles(2900 km) thick.(Mantle- Lithosphere )Made up of the crust and a tiny bit of the upper man tle, this layer is divided into several con sta ntly (very slowly) movi ng p lates of solid rock that hold the continents and ocea ns(Mantle- Asthenosphere )The p lates of the lithos p

7、here move (or float) on this hot, malleable semiliquid zone in the upper man tle, directly undern eath the lithos phere.1.2 (Ex plain their in flue nee on the Earth)(Molten)Eve n if the causes of the phenomenon rema in still difficult to determ ine, scie ntistsagree in say ing that the plan et's

8、 magn etic pole is in continual moveme nt.ltsdrift is most likely caused by the Earth's always movi ng molte n, in flue need by theIts driftfluctuatio ns in solar radiati on.Notcorres ponding to the p ositi on of the geogra phic po le, the mag netic pole moves at a rate of about 40 kilometers a

9、year. across the North Pole is, each and every year, closely mon itored by the GeologicSurvey of Can ada.(P artially Molte n)The microstructure of p artially molte n rocks p lays a key role in determ ining their p hysical prop erties. The area fractio n of in tergra nu lar con tact, con tiguity, gov

10、er ns the establishme nt of a skeletal framework of solid grains and con trols the effective elastic moduli of the aggregate. This work p rese nts a theoretical calculatio n of steady state grain sha pe, con tiguity, effective elastic moduli, and S and P wave velocities for a p artially molte n aggr

11、egate containing an app roximate melt volume fractio n of 0.09. The steady state microstructure is con trolled by surface tension gradie nts aris ing from in teractio n among adjace nt grains in a close-p acked aggregate. The ratio of viscosity betwee n the grains and the melt, as well as the cap il

12、lary nu mber, stron gly in flue nee the con tiguity(Solid)The earth formed app roximately 4.6 billi on years ago from a n ebular cloud of dust and gas that surr oun ded the sun. As the gas cooled, more solids formed. The dusty material accreted to the n ebular mid plane where it formed p rogressivel

13、y larger clu mps. Eve ntually, bodies of several kilometers in diameter formed; these are known as plan etesimals. The largest plan etesimals grew fastest, at the expense of the smaller on es. This p rocess continued un til an earth-sized planet had formed.Early in its formatio n, the earth must hav

14、e bee n comp letely molte n. The mai n source of heat at that time was p robably the decay 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 into three concen tric zon es: the crus

15、t, man tle and core. The crust exte nds dow nward from the surface to an average depthof 35 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 (Ex pl

16、ai n differe nces betwee n comp ositi onal and mecha ni cal boun daries)There 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 comp osed en tirely of basalt extruded at mid-ocea n ridges, result ing in a thi n (- 5 km), re

17、latively dense crust (3.0 g/cm 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

18、of a den ser material called p eridotite (3.4 g/cm3). This compo siti onal cha nge is p redicted by the behavior of seismic waves and it is con firmed in the few samp les of rocks from the man tle that we do have.At the core-ma ntle boun dary, compo siti on cha nges aga in. Seismic waves suggestthis

19、 material is of a very high den sity (10-13 g/cm3), which can on ly corres pond to a compo siti on of metals rather tha n rock. The p rese 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 t

20、o look at, and thus there is some controversy about its exact comp ositi on. Most scie ntists, however, believe that iron is the main con stitue nt.(Mechanical layers )The compo siti onal divisio ns of the earth were un derstood decades before the devel opment of the theory of p late tect onics - th

21、e idea that the earth 'surface con sists of large pl ates that move .By the 1970s, however, geologists bega n to realize that the pl ates had to be thicker tha n just the crust, or they would break apart as they moved. In fact, p lates con sist of the crust act ing together with the upp ermost p

22、art of the man tle; this rigid layer is called the lithos phere and it ran ges in thick ness from about 10 to 200 km. Rigid lithos pheric p lates "float" on a p artially molte n layer called the aesthe nosp here that flows like a very viscous fluid, like SillyPutty ?. It is important to no

23、te that although the asthenosphere can flow, it is not a liquid, and thus both S- and P-waves can travel through it. At a depth of 660 km, p ressure becomes so great that the man tle can no Ion ger flow, and this solid part of the man tle is called the mesos phere. The lithos pheric man tle, asthe n

24、osp here, and mesos phere all share the same compo siti on (that of p eridotite), but theirmecha ni cal prop erties are sig nifica ntly differe nt. Geologists ofte n refer to the asthe nosp here as the jelly in betwee n two p ieces of bread: the lithos phere and mesos phere.The core is also subdivid

25、ed into an inner and outer core. The outer core is liquid molte n metal while the inner core is solid. The dist in ctio n betwee n the inner andsee ” previouslyouter core was made in 1936 by Inge Lehma nn, a Dan ish seismologist, after impro veme nts in seismogra phs in the 1920s made it po ssible t

26、o un detectable seismic waves within the P-wave shadow zone. These fai nt waves in dicated that they had bee n refracted aga in within the core whe n 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 ,ma ntle tha

27、n they do in the crust, because it is compo sed of den ser material.Occurs in the source and in the surface of the earth and the sp read 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

28、- P Waves )Primary waves (or P waves) are the fastest moving waves, traveling at 1 to 5 miles per sec ond (1.6 to 8 kilometers per sec on d). They can p ass through solids, liquids and gases easily. As they travel through rock, the waves move tiny rock p articles back and forth - pu shi ng them apar

29、t and the n back together -in line with the directi on the wave is traveli ng. These waves typ ically arrive at the 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 onl

30、y p ass through solids. As S waves move, they dis place rock p articles outward, pu shi ng them perpen dicular to the p ath of the waves. This results in the first p eriod of rolli ng associated with earthquakes. Un like P waves, S waves don't move straight through the earth They on ly travel th

31、rough solid material, and so are stopped at the liquid layer in the Earth's core.(surface- L Waves )Un like body waves, surface waves (also known as long waves, or sim ply L waves) move along the surface of the Earth. Surface waves are to blame for most of an earthquake's earn age. They move

32、 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, which means they arrive the last. So the most intense shak ing usually comes at the end of an earthquake.2.3 (How do they move through the earth's surfac

33、e?)P waves-co mp ressi on-can travel solidsS waves-ri ppie waves-can't thought the solidsL waves-Rayleigh waves-gro und roll-travel ur ripple-love waves-Arular shori ng2.4(Ex plain how an alys ing these waves scie ntists are able to determ ine what is in side the Earth )Kno wledge of the Earth&#

34、39;s 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 at differi ng sp eeds through differe nt materials (and also, at differe nt sp eeds through material of differe nt states, i.e., liquid or sol

35、id). Because we know the size of the Earth, by measuri ng how long it takes to pick up on seismic activity on opp osite sides of the Earth, we can gauge about how 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

36、 as the Moho, is the boun dary betwee n the Earth's crust and the man tle. The Moho serves to sep arate both ocea nic crust and continen tal crust from un derly ing man tle. The Moho mostly lies en tirely within the lithos phere; on ly ben eath mid-ocea n ridges does the Moho also defi ne the li

37、thos phere-asthe nosp here 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 the abrupt in crease in the velocity of earthquake waves (sp ecifically P- waves) at this point.2.6(Ex plain how it was found?) 190

38、9 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 comp ositi on.3. plate tectonics3.1(What are tect on ic plates?)Tectonic plates are large plates of rock that make up the foundation

39、 of the Earth's crustand the sha pe of the con ti nen ts. Thetect onic pl ates comp rise the bottom of the crust and the top of the Earth's mantle.3.2(What the major p lates on a world map?)First the global lithos phere is divided into six p arts, n amely the Pacific p late, the Eurasia n pl

40、 ate, the In dia n Ocea n pl ate, pl ate, America, Africa and An tarctica pl ate tect onic pl ates.3.3(Ex pla in the Wage ner's theory 'con ti nen tal drift'. What was the evide nee that supp orted his theory? Why was it rejected at frist?)As evide nee, he no ted, as had others before hi

41、m, of the geogra phic correlati on in coastl ine p erimeters of South America and Africa. This was the feature that ledWage ner to inv estigate for other evide nces. His inv estigati ons revealed that moun tai n ran ges in South America and Africa, and strata and compo siti on of coal fields in Euro

42、pe and North America matched or lined up. Additi on ally, matchi ng rep tilia n fossils were found on either side of the ocea n, in dicat ing that the con ti nents were once joined together.Because he had no p hysical mecha nism to explain how his "isla nds" of rock could go freely sail in

43、g 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 ner's theory of continen tal drift and Theory of p late tect oni cs? )Continen tal drift theory was propo sed before the disc

44、overy of the mid-ocea nic ridges, whe n it was hypo thesized that the continents were actually plowing through the ocea ns. This theory was an atte mpt to ex plai n the com mon ality of fossils on oppo site sides of the Atla ntic Ocea n, and the observati on on maps of the Earth that the NorthAmeric

45、a n and South America n continents app eared to have bee n p ulled apart fromEuro pe and Africa. With the discovery of the mid-ocea nic ridges, where new crustal p late is being created, and subduct ion zon es, where pl ates are being destroyed, plate tecto nic theory was born; that the crust of the

46、 earth is divided into many segme nts that are in con sta nt moti on, that the ocea nic crust is con sta ntly being recycled-all drive n by heat from the Earth's in terior.3.5(Describe the evide nee that Theory of the p late tect oni cs.)To explain the phenomenon of con ti nen tal drift devel oped a geological theory. The theory that the earth's