2022年自然地理学专业英语 .docx

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1、精选学习资料 - - - - - - - - - Lecture 1 INTRODUCTION TO EARTH Major Concept I The planets in our solar system, including Earth, began to form out of a rotating disk of gas and dust about 4.6 billion years ago.Related or supporting concepts: The present view of the beginning of the solar system suggests t

2、hat a cloud of gas and dust was flattened into a disk by rotation. The density of the matter in the disk was greatest at its center and decreased toward the edges.The sun formed at the center of the disk where the temperature was highest and the planets formed at greater distances away from the cent

3、er.The compositions of the planets differ because of a natural sorting of elements in the cloud with distance from the center.The temperature of the early Earth was probably quite high due to: a. the gravitational capture of particles that released heat on impact, b. the increased pressure on the in

4、terior of the planet as it continued to grow, and c. the capture of radioactive elements that gave off heat when they decayed.During the first few hundred million years, the internal temperature rose high enough to melt iron and nickel. These heavy metals sank to form the core of the planet and disp

5、laced lighter material that rose to form chemically differentiated shells. Major Concept IIEarth s oceans originated early in the planetThere are two proposed sources of the water in the oceans.Related or supporting concepts: The oldest sedimentary rocks found that required water for their formation

6、 are 3.9 billion years old. This suggests that there are been oceans on Earth for roughly 4 billion years. Traditionally scientists have believed that the water in the oceans and atmosphere originated in e surface by volcanism. Earth s mantle and was brought to th Most magmas contain from 1% to 5% d

7、issolved gas by weight, most of which is water vapor. If we assume that the current rate of release of water vapor in volcanic eruptions has remained essentially constant for the past 4 billion years, then the volume of water expelledput out during that time would be roughly 100 times the volume of

8、todays oceans.A relatively new proposal is that a significant amount of water is added to Earth from space when small icy comets彗星enter Earthmosphere. The early atmosphere did not have any oxygen. The oxygen released from the interior of the planet would have combined with metals at the surface to p

9、roduce oxides. It wasnt until large amounts of oxygen were produced after plants formed that it began to accumulate in the atmosphere. Major Concept III There is compelling evidence that there may be other oceans in the solar system.Related or supporting concepts: Two of Jupiters moons, Europa and C

10、allisto, may have oceans beneath their icy s urfaces. Liquid oceans on Europa may be possible despite extremely low temperatures because of heat 名师归纳总结 - - - - - - -第 1 页,共 26 页精选学习资料 - - - - - - - - - generated by friction as it is deformed by Jupiter-producing gravitational force. Both moons have

11、induced magnetic fields indicating they consist partly of strongly conducting material. This may be liquid water with electrolytic salts. There is also some indication that Mars once had an ocean covering portions of its northern hemisphere. Major Concept IVThere are a variety of lines of indirect e

12、vidence that allow us to estimate Earths age about 4.5 to 4.6 billion years.Related or supporting concepts: Earth s original crust, that would have formed early in its history, has been destroyed or covered by active volcanism and tectonic processes. This is a reflection of the geologically active n

13、ature of the planet. Consequently, the oldest surface rocks we have found, roughly 4 billion years old, give us a minimum age for Earth rather than an actual age. Indirect evidence of Earths age includes:a. the dating of moon rocks at 4.2 billion years, b. the dating of meteorites at 4.5 to 4.6 bill

14、ion years, and c. theoretical calculations of the age of the sun as being roughly the same as the meteorites. We can determine the age of rocks that contain radioactive isotopes of elements that decay at constant, known rates. This is called radiometric dating. If a rock contains atoms of a specific

15、 radioactive isotope, half of them will decay into another element, called the daughter product, in a period of time called the half-life of the isotope. An example of this type of process would be Uranium235 and its daughter product Lead207 with a half-life of 704 million years. A rock that initial

16、ly contained 100 atoms of U235 and no Pb207 would have the following numbers of the two elements after the indicated elapsed times: There are several different parent-daughter radioactive pairs that occur in rocks. Each of the pairs has its own specific half-life, some quite long and others very sho

17、rt. Pairs with long half-lives are best for dating very old rocks while those with short half-lives are best for younger rocks. Ideally, an assigned date for a rock will be based on the use of more than one radioactive pair so that a check can be made on accuracy. Major Concept V Geologic time is of

18、ten difficult to grasp because of how long it is compared to all of human history to say nothing of the incredibly brief time span of a single human life.Related or supporting concepts Just as we divide time into segments like years, months, and days to identify both duration and some sense of posit

19、ion, we divide geologic time as well. The longest division is called an eon. Eons are divided into eras, eras are divided into periods, and periods into epochs.The geologic time scale and the history of evolution of life-forms is given in table 2.1.The eras, in order of most distant past to most rec

20、ent time, are: a. Precambrian, b. Paleozoic ancient life, c. Mesozoic intermediate life, and d. Cenozoic recent life.The divisions of geologic time were originally decided upon on the basis of the appearance and 名师归纳总结 - - - - - - -第 2 页,共 26 页精选学习资料 - - - - - - - - - disappearance of specific fossi

21、ls.The development of radiometric dating techniques allowed geologists to assign absolute dates to the different time divisions. Because of the difficulty we typically have in comprehending time spans as great as billions of years, it is often easier to imagine that the earth is much younger, say te

22、ns of years old, and then consider what major events occurred in that period of time. Suppose, for example, that rather than the earth being 4.6 billion years old, it is only 46 years old. Then we can recognize the following important events: a. 0 years of age: the earth formed b. the first several

23、years of the planets history have not been preserved in the record c. 6 years of age: the oldest discovered rocks were formed d. 12 years of age: the first living cells appeared e. 2223 years of age: photosynthesis began producing oxygen f. 31 years of age: there was sufficient oxygen in the atmosph

24、ere to allow the growth of complex cells that require oxygen g. 40 years of age: the first hard-shelled organisms appeared, to be preserved later as fossils h. 41 years of age: the first animals with backbones, called vertebrates, appeared i. 41 years and 8. months: land plants appeared and were sho

25、rtly followed by a period of time when fish were the dominant animal form 43 years of age: the appearance of reptiles j. k. 44 years of age: dinosaurs were abundant l. 45 years of age: the dinosaurs disappeared m. about a year ago: flowers appeared n. 4 months ago: mammals, birds, and insects were t

26、he dominant life forms o. 25 days ago: human ancestors appeared p. 11 days ago: the first member of the genus Homo appeared q. 30 minutes ago: modern civilization began r. 1 minute ago: the industrial revolution began Major concept VI Earth has a roughly spherical shape, bulging slightly at the equa

27、tor, with a surface that is remarkably smooth.Related or supporting concepts The earth is not a perfectly rigid body. As a result, its rotation causes it to bulge outward at the equator and be slightly flattened at the poles .Approximate values for the following figures are: a. average radius = 6371

28、 km or 3956 mi b. equatorial radius = 6378.4 km or 3961 mi c. polar radius = 6356.9 km or 3947 mi d. equatorial-polar radius = 21.5 km or 15 mi The unequal distribution of continents and ocean basins results in a further deformation of the planet from a perfect sphere to a shape that is similar to a

29、 pear.Although it seems as if the difference in elevation from the highest point on land to the deepest place on the sea floor is very large, it is really quite small compared to Earth size. The difference in surface elevation is less than 20 km compared to Earths radius of over 6000 km.名师归纳总结 - - -

30、 - - - -第 3 页,共 26 页精选学习资料 - - - - - - - - - If Earth was reduced to the size of a basketball or a grapefruit, its surface would be about as smooth as they are. Major Concept VII Exact position on Earth is determined by latitude and longitude.Related or supporting concepts: A grid of lines can be pl

31、aced over Earthsurface to serve as a reference system to determine location. There are two sets of lines that intersect one another to define latitude and longitude. Lines of latitude are drawn as circles parallel to the equator. These circles have steadily decreasing diameters as they get closer to

32、 the poles. Lines of latitude are also called parallels because all of the circles are in planes that are parallel to one another. Latitude is 0 at the equator and increases to 90 at the poles. From this it should be clear that latitude is measured as an internal angle from the center of the Earth a

33、way from the equator. By convention, latitudes south of the equator are negative and north of the equator are positive. One degree of latitude is equal to 60 nautical miles.Lines of longitude are sometimes called great circles because they are drawn by constructing circles perpendicular to the equat

34、or, that pass through both poles . diameter that is the same as Earths diameter.In this way, each circle has a Lines of longitude segment the planet in a way that is similar to the sections of an orange.Lines of longitude are also called meridians. The distance between meridians corresponds to an an

35、gle from the center of the earth between an arbitrarily chosen prime meridian, which is at 0 by definition, and a second meridian measured along the equator. The prime meridian passes through both poles and Greenwich, England .Longitude can be measured from 0360 moving eastward from the prime meridi

36、an, or from 0to +180E and 0 to -180W.The actual distance between meridians decreases away from the equator and becomes zero at the poles, where all meridians converge.Each degree of latitude or longitude can be divided into 60 minutes 60 and each minute into 6seconds 60 . Major Concept VIII Differen

37、ces in longitude can be related to differences in time between two locations because of Earths rotation.The rotation and revolution of the Earth around the Sun Related or supporting concepts: Earth rotates on its axis once every 24 hours. It follows therefore that it rotates through 360 of longitude

38、 each 24 hours. This is equivalent to 15 of longitude/1 hour or 15 of longitude/1 minute of time. The time at 0 longitude, or at Greenwich, England is called Greenwich Mean Time GMT. It is also known as Universal Time UT or ZULU Z time. The international date line is on the opposite side of the eart

39、h from Greenwich, England or the prime meridian. It corresponds to the 180 meridian. Because we know the rate of Earths rotation, we can determine our longitude simply by knowing the difference in time between our location and Greenwich, England. For example: Major Concept IX Characteristics of Eart

40、hs surface are often shown on maps and charts.名师归纳总结 - - - - - - -第 4 页,共 26 页精选学习资料 - - - - - - - - - 中国地势图1：32000000 Related or supporting concepts: Maps and charts illustrate three-dimensional shapes on two-dimensional surfaces. Surface features on land are often illustrated with maps.Seafloor fe

41、atures are often illustrated with charts. the sky. Charts are also used to illustrate features in Three-dimensional features can never be perfectly illustrated on two-dimensional maps and charts. As a result, there is always some distortion of real features.Different map projections will produce dif

42、ferent types and degrees of distortion. When choosing a specific projection you need to carefully consider which one will produce the least distortion of the features you are interested in.There are three basic types of projections : a. cylindrical, b. conic, and c. tangent plane. The sea floor is o

43、ften illustrated using a bathymetric chart . chart connect points of equal depth.Contour lines on a bathymetric A chart that shows regions of varying depth by variations in color, shading, or perspective drawing is called a physiographic map.Three-dimensional, color images are generated by computer

44、from detailed sonar data Major Concept X Physical, biological, and chemical processes on the planet are all influenced by temporal changes or cycles that occur with different periods and are due to Earths rotation on its axis and its movement around the sun.Related or supporting concepts: There are

45、two natural periods that influence processes on Earth. These are caused by the daily rotation of the planet on its axis which gives us night and day, and the yearly rotation of the earth around the sun which gives us the changing seasons.We experience seasonal variations in climate because Earths ro

46、tational axis is tilted away from a line drawn perpendicular to the plane of its orbit around the sun by 23.Earth s tilt results in an annual migration of the apparent position of the sun in the sky from being directly overhead at noon somewhere between 23.S and 23.N throughout the year. Outside of

47、this band of latitude centered on the equator, the sun will never appear to be directly overhead even when it has risen in the sky to its highest point at noon. The Northern Hemisphere is tilted toward the sun during Northern Hemisphere summers and is warmer because the intensity of solar radiation is greater at the surface when the suns rays are more nearly perpendicular to the surface. its