2022年自然地理学专业英语 .pdf

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1、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 that a cloud of gas and d

2、ust 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 center.The compositions of t

3、he 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 interior of the planet as

4、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 displaced lighter material t

5、hat rose to form chemically differentiated shells. Major Concept (II)Earth s oceans originated early in the planet s history. There 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 are 3.9 b

6、illion 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 Earth s mantle and was brought to the surface by volcanism. Most magmas contain from 1% to 5% dissolved ga

7、s 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 expelled(put out) during that time would be roughly 100 times the volume of today s o

8、ceans.A relatively new proposal is that a significant amount of water is added to Earth from space when small icy comets彗星enter Earth s atmosphere. 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 prod

9、uce 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 Jupiter s moons, Europa and Ca

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

11、have 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 (IV)There are a variety of lines of ind

12、irect evidence that allow us to estimate Earth s age as being 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 geol

13、ogically active nature 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 Earth s age includes:a. the dating of moon rocks at 4.2 billion years, b. the dating of meteorites

14、at 4.5 to 4.6 billion 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 a

15、toms of a specific 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

16、 rock that initially 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 a

17、nd others very short. 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)

18、Geologic time is often 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 an

19、d some sense of position, 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 dis

20、tant past to most recent 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 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 2 页，共 26 页disa

21、ppearance of specific fossils.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 ea

22、rth is much younger, say tens 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 f

23、ormed b. the first several 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. 22 23 years of age: photosynthesis began producing oxygen f. 31 years of age: there was suff

24、icient oxygen in the atmosphere 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

25、plants appeared and were shortly followed by a period of time when fish were the dominant animal form j. 43 years of age: the appearance of reptiles 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: mammal

26、s, birds, and insects were the 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,

27、 bulging slightly at the equator, 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

28、are: a. average radius = 6371 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

29、to a shape that is similar to a 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 s size. The difference in surface elevation is less than 20 km compared to Earths ra

30、dius of over 6000 km.精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 3 页，共 26 页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 c

31、oncepts: A grid of lines can be placed over Earth s surface 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 decre

32、asing diameters as they get closer to 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

33、 angle from the center of the Earth away 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 constructi

34、ng circles perpendicular to the equator, that pass through both poles . In this way, each circle has a diameter that is the same as Earth s diameter.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

35、between meridians corresponds to an angle from the center of the earth between an arbitrarily chosen prime meridian, which is at 0by definition, and a second meridian measured along the equator. The prime meridian passes through both poles and Greenwich, England .Longitude can be measured from 0 360

36、 moving eastward from the prime meridian, 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

37、60 seconds (60 ). Major Concept (VIII)Differences in longitude can be related to differences in time between two locations because of Earth s 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 the

38、refore that it rotates through 360 of longitude 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 in

39、ternational date line is on the opposite side of the earth from Greenwich, England or the prime meridian. It corresponds to the 180 meridian. Because we know the rate of Earth s rotation, we can determine our longitude simply by knowing the difference in time between our location and Greenwich, Engl

40、and. For example: Major Concept (IX)Characteristics of Earths surface are often shown on maps and charts.精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 4 页，共 26 页中国地形图1：32000000 Related or supporting concepts: Maps and charts illustrate three-dimensional shapes on two-dimensional surfaces.Surface fe

41、atures on land are often illustrated with maps.Seafloor features are often illustrated with charts. Charts are also used to illustrate features in the sky. Three-dimensional features can never be perfectly illustrated on two-dimensional maps and charts. As a result, there is always some distortion o

42、f real features.Different map projections will produce different 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. cylin

43、drical, b. conic, and c. tangent plane. The sea floor is often illustrated using a bathymetric chart . Contour lines on a bathymetric chart connect points of equal depth.A chart that shows regions of varying depth by variations in color, shading, or perspective drawing is called a physiographic map.

44、Three-dimensional, color images are generated by computer 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 movemen

45、t around the sun.Related or supporting concepts: There are 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

46、experience seasonal variations in climate because Earth s rotational 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 so

47、mewhere between 23? S and 23? N throughout the year. Outside of 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

48、 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. At this time the Southern Hemisphere experiences its winter as it is tilted away from the sun. There are four parallels of latitude that have spe

49、cial names; these are: Latitude Name 66? N Arctic Circle 23? N Tropic of Cancer 23? S Tropic of Capricorn 精选学习资料 - - - - - - - - - 名师归纳总结 - - - - - - -第 5 页，共 26 页66? S Antarctic Circle On the summer solstice, which usually occurs around June 22, the sun will be directly overhead the Tropic of Cance

50、r and there will be 24 hours of daylight above the Arctic Circle. This is the day with the longest period of daylight in the Northern Hemisphere and the shortest in the Southern Hemisphere. The sun will not rise at all at latitudes farther south than the Antarctic Circle.On the autumnal equinox, on