自然地理学专业英语

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 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 center.

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 interior 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 displaced lighter material that 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 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 Earth’s mantle and was brought to the surface by volcanism.

Most magmas contain from 1% to 5% dissolved 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 expelled(put out) during that time would be roughly 100 times the volume of today’s 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 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 produce oxides.

It wasn't 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 Callisto, may have oceans beneath their icy surfaces.

Liquid oceans on Europa may be possible despite extremely low temperatures because of heat generated by friction as it is deformed by Jupiter’s tide-producing gravitational force.

Both moons 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 indirect 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 geologically 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 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 atoms 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 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 and 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)

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 and 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 distant 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 disappearance 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 earth 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 formed

b. the first several years of the planet's 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 sufficient 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 8½ months: land 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: mammals, 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, 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 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 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 Earth's radius of over 6000 km.

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 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 decreasing 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 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 constructing 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 between meridians corresponds to an angle 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 0°–360° moving eastward from the prime meridian, or from 0° to +180°E and 0° to -180°W.

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 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 therefore 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 international 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, England. For example:

Major Concept (IX)

Characteristics of Earth's surface are often shown on maps and charts.

中国地形图

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 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 of 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. cylindrical,

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.

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 Earth's rotation on its axis and its movement 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 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 23½°.

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 23½°S and 23½°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 summers and is warmer because the intensity of solar radiation is greater at the surface when the sun's 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 special names; these are:

Latitude Name

66½°N Arctic Circle

23½°N Tropic of Cancer

23½°S Tropic of Capricorn

66½°S Antarctic Circle

On the summer solstice, which usually occurs around June 22, the sun will be directly overhead the Tropic of Cancer 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 about September 23, the sun will be directly overhead the equator and the amount of daylight will be the same everywhere.

On the winter solstice, around December 21, the sun will be directly overhead the Tropic of Capricorn and there will be 24 hours of daylight above the Antarctic Circle and perpetual darkness above the Arctic Circle. This will be the day with the longest period of sunlight in the Southern Hemisphere and the shortest in the Northern Hemisphere.

On the vernal equinox, roughly March 21, the sun will have moved northward again to stand directly over the equator.

The greatest annual change in climate occurs at mid-latitudes in what are called the temperate zones. At low latitudes it is relatively warm throughout the year and at high latitudes it remains fairly cold.

The orbit the earth takes around the sun is elliptical, so the distance between the earth and the sun changes through the year. The distance is greatest during the Northern Hemisphere summer and least during the Northern Hemisphere winter. It is important to remember that the seasons are not due to the variable distance from the sun (otherwise we should expect summer in the Northern Hemisphere when we are closest to the sun in the end of December), but rather they are controlled by what hemisphere is tilted toward the sun's rays.

Major Concept (XI)

Earth is essentially a closed system. As such, all of the water available to the planet moves through different reservoirs where it is stored for varying periods of time before moving on.

Related or supporting concepts:

Water can be found in all three states of matter in the earth system: solid (ice), liquid, and gas (water vapor).

At any given time a water molecule will be located in a specific reservoir. Examples of reservoirs include the atmosphere, rivers, lakes, the oceans, glaciers, and groundwater, to name a few.

Water will not remain indefinitely in a single reservoir; rather, it will be cycled from one reservoir to another by such processes as evaporation, precipitation, transpiration, sublimation, and runoff.

Transpiration is the release of water by plants. Sublimation is a phase change of water from solid to gas, or from ice to water vapor.

The cycling of water from one reservoir to another is called the hydrologic cycle. The hydrologic cycle can be seen diagrammatically in figure 2.17 in your text.

In the simplest possible description, the movement of water from one reservoir to another can be described in part by the following table:

Reservoir Water lost via Water gained via

continents evaporation precipitation

runoff

transpiration

sublimation

oceans evaporation precipitation

runoff

sublimation

atmosphere precipitation evaporation

transpiration

sublimation

The amount of water stored in different reservoirs can vary greatly. The largest volume of water is stored in the oceans (about 98 percent) and the least amount is stored in the atmosphere (about .001 percent).

Major Concept (XII)

The largest water reservoir in the earth system in terms of the volume of water stored is the oceans.

Related or supporting concepts:

Roughly 71 percent of the surface of the planet is covered by the oceans. This leaves only 29 percent covered by the continents.

The surface area of the oceans is approximately 140 million square miles or 362 million square kilometers.

The volume of water held in the oceans is an incredible 1.35 billion cubic kilometers. This amount of water is so great that it is difficult to grasp.

If Earth was a smooth ball without any continents to interrupt the oceans and a flat sea floor, the water held in the oceans would cover the globe to a uniform depth of about 1.7 miles (2645 meters or 8680 feet).

Adding all of the rest of the water trapped in other reservoirs would raise the level of this global sea by 75 meters to about 2720 meters or 8924 feet.

Major Concept (XIII)

The continents are not uniformly distributed on Earth. In addition, the percentage of the planet's surface at any given elevation is not constant.

The only latitude band where there is more land than water, with the exception of Antarctica, is between 45°–70°N.

The Southern Hemisphere is dominated by oceans while most land is in the Northern Hemisphere .

Related or supporting concepts:

As mentioned previously, continents cover about 29 percent of Earth's surface. Roughly 70 percent of all land is found in the Northern Hemisphere, and most of it at mid-latitudes.

Take a look at figure 2.19 to see the distribution of land and water with latitude.

The percent of land and sea floor, as well as the percent of the total surface area of the planet, that is at any specific elevation above or depth below sea level is shown in figure 2.20. This plot is called the hypsographic curve.

Among the things we can learn from the hypsographic curve are:

a. mean elevation of land = 840 m

b. mean depth of the oceans = 3729 m

c. about 20 percent of land is higher than 2 km above sea level

d. about 85 percent of sea floor is deeper than 2 km below sea level

The highest elevation on land, Mt. Everest at 8850 m, is closer to sea level than the deepest spot in the oceans, the Challenger Deep of the Mariana Trench at 11,030 m.

The great difference in height between the continents and the sea floor is due to the large difference in the types of rocks that make up continents and sea floor. Continental rocks have a lower density than seafloor rocks.

Major Concept (XIV)

The world's seawater can be divided into four distinct oceans: the Pacific, the Atlantic, the Indian, and the Arctic.

Related or supporting concepts:

The three largest oceans (Pacific, Atlantic, Indian) all join in the Southern Hemisphere around Antarctica.

The Pacific Ocean is the largest with a surface area that is slightly larger than the sum of the other three. The Pacific also holds the greatest volume of water and has the greatest average depth.

The Atlantic Ocean is unique in that it extends the greatest distance north and south. It is a relatively narrow ocean and is the third deepest.

The Indian Ocean is different because it is entirely in the Southern Hemisphere. It is second deepest.

The Arctic Ocean is the smallest and shallowest of the four.

Each ocean is bounded roughly by continents, has its own distinct water masses, and well-defined surface currents.

A large body of seawater that is bounded by land and smaller than an ocean is called a mediterranean or a sea. Examples include the Arctic Sea, the Gulf of Mexico, the Mediterranean Sea, the Caribbean Sea, and the South China Sea.

Major Concept (XV)

Location at sea is determined by a number of different methods depending on distance from land and position on the globe. Most methods rely on some sort of electronic navigational equipment as opposed to the astronomical methods used in the past.

Related or supporting concepts:

There are three principal systems used in modern navigation:

a. radar : "radio detecting and ranging"

b. loran : "long-range navigation"

c. satellite navigation

Radar systems emit bursts of energy that travel outward and then return after reflecting off distant objects. By carefully measuring the travel time of the reflected energy, you can determine distance quite accurately. Radar is only useful when you are close enough to land for signals to be reflected back to the vessel.

Loran systems utilize fixed stations that transmit radio waves at specific frequencies. A loran receiver on board a ship can detect these transmissions. The difference in arrival time of the signals from pairs of stations is a measure of distance from the stations. Unlike radar, loran can be used far from land as long as the vessel is within receiving distance of loran stations. In addition, loran units can be interfaced with computers to automatically calculate latitude and longitude and to determine the ship's course to some pre-determined location.

The most accurate technique is satellite navigation. By monitoring signals from orbiting satellites, it is possible to obtain a location with an accuracy as great as 30 meters (or about 100 feet).

Modern electronic navigation methods permit the determination of location in any kind of weather and at any time of day. Small Global Positioning System (GPS) receivers are now routinely used by hikers, hunters, boaters, and others who need to know their location in the outdoors.

GPS Satellite

GPS Receiver

二、

IntroductionWords

Some useful vocabulary

Geography

Physical geography

Human geography

Geographical Information system

• Physical geography

Climate climatology meteorology

Geomorphology landform topography

Water Hydrology hydrosphere

Vegetation plant Biosphere

Soil Pedosphere

Air Atmosphere

Rock Lithosphere Geology

• physical geography studies the spatial patterns of weather and climate, soils, vegetation, animals, water in all its forms, and landforms. Physical geography also examines the interrelationships of these phenomena to human activities. This sub-field of geography is academically known as the Human-Land Tradition. This area of geography has seen very keen interest and growth in the last few decades because of the acceleration of human induced environmental degradation. Thus, physical geography's scope is much broader than the simple spatial study of nature. It also involves the investigation of how humans are influencing nature.

• Geomorphology - studies the various landforms on the Earth's surface.

• Pedology - is concerned with the study of soils.

• Biogeography - is the science that investigates the spatial relationships of plants and animals.

• Hydrology - is interested in the study of water in all its forms.

• Meteorology - studies the circulation of the atmosphere over short time spans.

• Climatology - studies the effects of weather on life and examines the circulation of the atmosphere over longer time spans.

• Geology - studies the form of the Earth's surface and subsurface, and the processes that create and modify it.

• Ecology - the scientific study of the interactions between organisms and their environment.

• Oceanography - the science that examines the biology, chemistry, physics, and geology of oceans.

• Cartography - the technique of making maps.

• Astronomy - the science that examines celestial bodies and the cosmos.  

• The development of Geography

After 1950, the following two forces largely determined the nature of physical geography:

• (1). The Quantitative Revolution - measurement became the central focus of research in Physical Geography. It was used primarily for hypothesis testing. With measurement came mapping, models, statistics, mathematics, and hypothesis testing. The quantitative revolution was also associated with a change in the way in which physical geographers studied the Earth and its phenomena. Researchers now began investigating process rather than mere description of the environment.

• (2). The study of Human/Land Relationships - the influence of human activity on the environment was becoming very apparent after 1950. As a result, many researchers in physical geography began studying the influence of humans on the environment. Some of the dominant themes in these studies included: environmental degradation and resource use; natural hazards and impact assessment; and the effect of urbanization and land-use change on natural environments.

• The following list describes some of the important future trends in physical geography research:

(1). Continued development of applied physical geography for the analysis and correction of human-induced environmental problems. A student of applied physical geography uses theoretical information from the field of physical geography to manage and solve problems related to natural phenomena found in the real world.

• (2). Remote Sensing - Advances in technology have caused the development of many new instruments for the monitoring of the Earth's resources and environment from airborne and space platforms. Also see

section 2e. The most familiar use of remote sensing technology is to monitor the Earth's weather for forecasting

• (3). Geographic Information Systems - A geographic information system (GIS) merges information in a computer database with spatial coordinates on a digital map. Geographic information dystems are becoming increasingly more important for the management of resources.

• Geologic Time Scale

Lecture 2

• Geologic Time Scale

• New words

Cenozoic Era

Quaternary Period Tertiary Period

Mesozoic Era

Cretaceous Period Jurassic Period Triassic Period

Paleozoic Era

Permian Period Carboniferous Period Devonian Period Silurian Period Ordovician Period Cambrian Period

• 一、THE CENOZOIC ERA

• The Cenozoic Era is the most recent of the three major subdivisions of geologic time.

• The Cenozoic Era spans only about 65 million years, from the end of the Cretaceous Period (Mesozoic Era), and the extinction of non-avian dinosaurs, to the present. The Cenozoic is sometimes called the Age of Mammals, because the largest animals found on land during this time have been mammals. This is a misnomer for several reasons. First, the history of mammals began long before the Cenozoic Era began. Second, the diversity of life during the Cenozoic is far wider than mammals. The Cenozoic could also be called the "Age of Insects," "Age of Teleost Fish," "Age of Birds," or the "Age of Flowering Plants" just as accurately.

• Origin of the Term

Cenozoic (Cainozoic) [1840]. Established by John Phillips in 1840 (with further discussion in 1841) as broad, interpretive categories of rock units based on overall fossil content. Reflected middle and late animal life. Note, Cainozoic (actually Kainozoic in 1840, re-spelled Cainozoic in 1841) is the preferred usage in Great Britain.

• The Cenozoic Era is divided into two main sub-divisions: the Tertiary and the Quaternary. Most of the Cenozoic is the Tertiary, from 65 million years ago to approximately 2.5 million years ago. The Quaternary includes only the last 2.5 million years.

• Quaternary Period

The Quaternary is a subdivision of geological time (the Quaternary Period) which covers the last two million years up to the present day. (The exact duration is a matter of debate with estimates of the onset of the Quaternary Period placed at between 1.8 million years and 2.6 million years by different authors) The Quaternary and the Tertiary Periods together form the Cenozoic Era. The Quaternary can be subdivided into two epochs; the Pleistocene (two million years to ten thousand years ago) and the Holocene (ten thousand years ago to the present day).

• Origin of the Term

Quaternary System. [1829] In the Seine Basin, P.G. Desnoyers classified some marine, lacustrine, alluvial, and volcanic rock above the Tertiary as Quaternary.

• The characteristics of Quaternary

The Quaternary Period has been one of extraordinary changes in global environment as well as the period during which much of hominid evolution took place.

• Quaternary time scale indicated by variation of isotopic oxygeon

• Tertiary Period

• Period of geological time 65 to 2.5 million years ago, divided into five epochs: Palaeocene, Eocene, Oligocene, Miocene, and Pliocene. During the Tertiary period, mammals took over all the ecological niches left vacant by the extinction of the dinosaurs, and became the prevalent land animals. The continents took on their present positions, and climatic and vegetation zones as we know them became established. Within the geological time column the Tertiary follows the Cretaceous period and is succeeded by the Quaternary period.

• Origin of the Term

Tertiary System. [1760] Named by Giovanni Arduino as the uppermost part of his three-fold subdivision (this was one of the first rudimentary time frameworks) of mountains in northern Italy. The Tertiary became a formal period and system when Lyell published his work describing further subdivisions (epochs) of the Tertiary.

• The characteristics of Tertiary

At the beginning of the Tertiary, the outlines of the North American continent were very similar to those of today; by the close of the period, Europe also had emerged substantially in its present form. Marine submergences in Europe were moderately extensive, but in North America they never went beyond the Atlantic, Gulf, and Pacific coasts and the lower Mississippi valley. These inundations took place chiefly in the Eocene, Oligocene, and Miocene epochs, the continents being generally emergent in the Pliocene epoch.

Life in Tertiary period

The Tertiary formations of either unconsolidated sediments or quite soft rocks are widespread. In the Tertiary, Gondwanaland finally split completely apart, and India collided with the Eurasian plate. The previously existing mountain ranges of North America were again elevated, the Alps, Pyrenees, Carpathians, and other ranges were formed in Europe, and in Asia the Himalayas arose. Widespread volcanic activity was prevalent.

At the beginning of the period the mammals replaced the reptiles as the dominant animals; each epoch was marked by striking developments in mammalian life. Modern types of birds, reptiles, amphibians, fishes, and invertebrates either were already numerous at the beginning of the period or appeared early in its history.

• 二、Mesozoic Era

• The Mesozoic is divided into three time periods: the Triassic (245-208 Million Years Ago), the Jurassic (208-146 Million Years Ago), and the Cretaceous (146-65 Million Years Ago).

• Mesozoic means "middle animals", and is the time during which the world fauna changed drastically from that which had been seen in the Paleozoic. Dinosaurs, which are perhaps the most popular organisms of the Mesozoic, evolved in the Triassic, but were not very diverse until the Jurassic. Except for birds, dinosaurs became extinct at the end of the Cretaceous. Some of the last dinosaurs to have lived are found in the late Cretaceous deposits of Montana in the United States.

• The Mesozoic was also a time of great change in the terrestrial vegetation. The early Mesozoic was dominated by ferns(蕨类), cycads（苏铁）, ginkgophytes（银杏类）, bennettitaleans（苏铁属）, and other unusual plants. Modern gymnosperms（裸子植物）, such as conifers（松类）, first appeared in their current recognizable forms in the early Triassic. By the middle of the Cretaceous, the earliest angiosperms（被子植物） had appeared and began to diversify, largely taking over from the other plant groups.

• The Cretaceous Period

144 to 65 Million Years Ago

• The Cretaceous is usually noted for being the last portion of the “Age of Dinosaurs”, but that does not mean that new kinds of dinosaurs did not appear then. It is during the Cretaceous that the first ceratopsian （有角类）and pachycepalosaurid（肿头龙） dinosaurs appeared. Also during this time, we find the first fossils of many insect groups, modern mammal and bird groups, and the first flowering plants.

K/T Boundary

• The breakup of the world-continent Pangaea, which began to disperse during the Jurassic, continued. This led to increased regional differences in floras and faunas between the northern and southern continents.

• The end of the Cretaceous brought the end of many previously successful and diverse groups of organisms, such as non-avian dinosaurs and ammonites. This laid open the stage for those groups which had previously taken secondary roles to come to the forefront. The Cretaceous was thus the time in which life as it now exists on Earth came together.

• The Jurassic Period

206 to 144 Million Years Ago

• Great plant-eating dinosaurs roaming the earth, feeding on lush growths of ferns and palm-like cycads（苏铁） and bennettitaleans（本内苏铁）. . . smaller but vicious carnivores（食肉动物） stalking the great herbivores. . . oceans full of fish, squid（鱿鱼）, and coiled ammonites（菊石类）, plus great ichthyosaurs（鱼龙类） and long-necked plesiosaurs（>蛇颈龙）. . . vertebrates taking to the air, like the pterosaurs（翼龙） and the first birds. . . this was the Jurassic Period, beginning approximately 210 million years ago and lasting for 70 million years of the Mesozoic Era.

The life of Jurassic period

• The origin of term

• Named for the Jura Mountains on the border between France and Switzerland, where rocks of this age were first studied, the Jurassic has become a household word with the success of the movie Jurassic Park. Outside of Hollywood, the Jurassic is still important to us today, both because of its wealth of fossils and because of its economic importance -- the oilfields of the North Sea, for instance, are Jurassic in age.

• The Triassic Period

248 to 206 Million Years Ago

• In many ways, the Triassic was a time of transition. It was at this time that the world-continent of Pangaea existed, altering global climate and ocean circulation. The Triassic also follows the largest extinction event in the history of life, and so is a time when the survivors of that event spread and recolonized.

• The organisms of the Triassic can be considered to belong to one of three groups: holdovers from the Permo-Triassic extinction, new groups which flourished briefly, and new groups which went on to dominate the Mesozoic world. The holdovers included the lycophytes(石松属植物), glossopterids（龙舌属）, and dicynodonts（二齿兽）. While those that went on to dominate the Mesozoic world include modern conifers, cycadeoids（拟苏铁目）, and the dinosaurs.

• 三、The Paleozoic Era

543 to 248 Million Years Ago

• The Paleozoic is bracketed by two of the most important events in the history of animal life. At its beginning, multicelled animals underwent a dramatic “explosion” in diversity, and almost all living animal phyla（phylum门） appeared within a few millions of years. At the other end of the Paleozoic, the largest mass extinction in history wiped out approximately 90% of all marine animal species. The causes of both these events are still not fully understood and the subject of much research and controversy. Roughly halfway in between, animals, fungi, and plants alike colonized the land, the insects took to the air.

• The origin of term

• The Paleozoic took up over half of the Phanerozoic, approximately 300 million years. During the Paleozoic there were six major continental land masses; each of these consisted of different parts of the modern continents. For instance, at the beginning of the Paleozoic, today's western coast of North America ran east-west along the equator, while Africa was at the South Pole. These Paleozoic continents experienced tremendous mountain building along their margins, and numerous incursions and retreats of shallow seas across their interiors. Large limestone outcrops, like the one shown above, are evidence of these periodic incursions of continental seas.

• Many Paleozoic rocks are economically important. For example, much of the limestone quarried for（采矿） building and industrial purposes, as well as the coal deposits of western Europe and the eastern United States, were formed during the Paleozoic.

• The Permian

290 to 248 Million Years Ago

• The Permian period lasted from 290 to 248 million years ago and was the last period of the Paleozoic Era. The distinction between the Paleozoic and the Mesozoic is made at the end of the Permian in recognition of the largest mass extinction recorded in the history of life on Earth. It affected many groups of organisms in many different environments, but it affected marine communities the most by far, causing the extinction of most of the marine invertebrates of the time. Some groups survived the Permian mass extinction in greatly diminished numbers, but they never again reached the ecological dominance they once had, clearing the way for another group of sea life. On land, a relatively smaller extinction of diapsids and synapsids cleared the way for other forms to dominate, and led to what has been called the "Age of Dinosaurs". Also, the great forests of fern-like plants shifted to gymnosperms, plants with their offspring enclosed within seeds. Modern conifers, the most familiar gymnosperms of today, first appear in the fossil record of the Permian. In all, the Permian was the last of the time for some organisms and a pivotal point for others, and life on earth was never the same again.

• The global geography of the Permian included massive areas of land and water. By the beginning of the Permian, the motion of the Earth's crustal plates had brought much of the total land together, fused in a supercontinent known as Pangea. Many of the continents of today in somewhat intact form met in Pangea (only Asia was broken up at the time), which stretched from the northern to the southern pole. Most of the rest of the surface area of the Earth was occupied by a corresponding single ocean, known as Panthalassa, with a smaller sea to the east of Pangea known as Tethys.

• Models indicate that the interior regions of this vast continent were probably dry, with great seasonal fluctuations, because of the lack of the moderating effect of nearby bodies of water, and that only portions received rainfall throughout the year. The ocean itself still has little known about it. There are indications that the climate of the Earth shifted at this time, and that glaciation decreased, as the interiors of continents became drier.

• The Carboniferous

354 to 290 Million Years Ago

• The Carboniferous Period occurred from about 354 to 290 million years ago during the late Paleozoic Era. The term "Carboniferous" comes from England, in reference to the rich deposits of coal that occur there. These deposits of coal occur throughout northern Europe, Asia, and midwestern and eastern North America. The term "Carboniferous" is used throughout the world to describe this period, although this period has been separated into the Mississippian (Lower Carboniferous) and the Pennsylvanian (Upper Carboniferous) in the United States. This system was adopted to distinguish the coal-bearing layers of the Pennsylvanian from the mostly limestone Mississippian, and is a result of differing stratigraphy on the different continents.

• In addition to having the ideal conditions for the beginnings ofcoal, several major biological, geological, and climatic events occurred during this time. One of the greatest evolutionary innovations of the Carboniferous was the amniote（脊椎动物） egg, which allowed for the further exploitation of the land by certain tetrapods（四足动物）. The amniote egg allowed the ancestors of birds, mammals, and reptiles to reproduce on land by preventing the desiccation of the embryo inside. There was also a trend towards mild temperatures during theCarboniferous, as evidenced by the decrease in lycopods（石松属植物） and large insects and an increase in the number of tree ferns.

Life in carboniferous period

• Geologically, the Late Carboniferous collision of Laurussia (present-day Europe and North America) into Godwanaland (present-day Africa and South America) produced the Appalachian mountain belt of eastern North America and the Hercynian Mountains in the United Kingdom. A further collision of Siberia and eastern Europe created the Ural Mountains.

• The stratigraphy of the Lower Carboniferous can be easilydistinguished from that of the Upper Carboniferous. The environment of the Lower Carboniferous in North America was heavily marine, when seas covered parts of the continents. As a result, most of the mineral found in Lower Carboniferous is limestone, which are composed of the remains of crinoids（海百合类）, lime-encrusted green algae, or calcium carbonate shaped by waves. The North American Upper Carboniferous environment was alternately terrestrialand marine, with the transgression and regression of the seas caused by glaciation. These environmental conditions, with the vast amount of plant material provided by the extensive coal forests, allowed for the production of coal. Plant material did not decay when the seas covered them and pressure and heat eventually built up over the millions of years to transform the plant material to coal.

• The Devonian

417 to 354 Million Years Ago

• The Rhynie Chert in Scotland is a Devonian age deposit containing fossils of both Zosterophyllophytes and Trimerophytes, the two major lines of vascular plants. This indicates that prior to the start of the Devonian, the first major radiations of the plants had already happened. The oldest known vascular plants in the Northern Hemisphere are Devonian.

• The vegetation of the early Devonian consisted primarily of small plants, the tallest being only a meter tall. By the end of the Devonian, ferns, horsetails and seed plants had also appeared, producing the first trees and the first forests.

Life on Devonian land

Life in Devonian Sea

• Also during the Devonian, two major animal groups colonized the land. The first tetrapods(四足动物), or land-living vertebrates, appeared during the Devonian, as did the first terrestrial arthropods（节肢动物）, including wingless insects and the earliest arachnids（蜘蛛类）. In the oceans, brachiopods（腕足类） flourished. Crinoids(海百合类) and other echinoderms（棘皮类动物）, tabulate and rugose（有皱纹的） corals, and ammonites（菊石类） were also common. Many new kinds of fish appeared.

• During the Devonian, there were three major continental masses: North America and Europe sat together near the equator, much of their current land underneath seas. To the north lay a portion of modern Siberia. A composite continent of South America, Africa, Antarctica, India, and Australia dominated the southern hemisphere.

• The Silurian

443 to 417 Million Years Ago

• The Silurian (443 to 417 million years ago) was a time when the Earth underwent considerable changes that had important repercussions for the environment and life within it. The Silurian witnessed a relative stabilization of the earth's general climate, ending the previous pattern of erratic climatic fluctuations. One result of these changes was the melting of large glacial formations. This contributed to a substantial rise in the levels of the major seas.

• Coral reefs made their first appearance during this time, and the Silurian was also a remarkable time in the evolution of fishes. Not only does this time period mark the wide and rapid spread of jawless fish, but also the highly significant appearances of both the first known freshwater fish as well as the first fish with jaws. It is also at this time that our first good evidence of life on land is preserved, including relatives of spiders and centipedes, and also the earliest fossils of vascular

（脉管的） plants

Life in Silurian period

• The Ordovician

490 to 443 Million Years Ago

• The Ordovician period began approximately 510 million years ago, with the end of the Cambrian, and ended around 445 million years ago, with the beginning of the Silurian. At this time, the area north of the tropics was almost entirely ocean, and most of the world's land was collected into the southern super-continent Gondwana. Throughout the Ordovician, Gondwana shifted towards the South Pole and much of it was submerged underwater.

• The Ordovician is best known for the presence of its diverse marine invertebrates, including graptolites（笔石）, trilobites（三叶虫）, brachiopods（腕足类）, and the conodonts (early vertebrates). A typical marine community consisted of these animals, plus red and green algae, primitive fish, cephalopods（头足类）, corals, crinoids, and gastropods（腹足类）. More recently, there has been found evidence of tetrahedral spores that are similar to those of primitive land plants, suggesting that plants invaded the land at this time.

• From the Early to Middle Ordovician, the earth experienced a milder climate in which the weather was warm and the atmosphere contained a lot of moisture. However, when Gondwana finally settled on the South Pole during the Late Ordovician, massive glaciers formed causing shallow seas to drain and sea levels to drop. This likely caused the mass extinctions that characterize the end of the Ordovician, in which 60% of all marine invertebrate genera and 25% of all families went extinct.

• The Cambrian Period

543 to 490 Million Years Ago

• The Cambrian Period marks an important point in the history of life on earth; it is the time when most of the major groups of animals first appear in the fossil record. This event is sometimes called the "Cambrian Explosion", because of the relatively short time over which this diversity of forms appears. It was once thought that the Cambrian rocks contained the first and oldest fossil animals, but these are now to be found in the earlier Vendian strata.

Life in Cambrian period

Lecture 3

• Rock Types

• Geologists classify rocks in three groups, according to the major Earth processes that formed them. The three rock groups are igneous, sedimentary, and metamorphic rocks. Anyone who wishes to collect rocks should become familiar with the characteristics of these three rock groups. Knowing how a geologist classifies rocks is important if you want to transform a random group of rock specimens into a true collection.

• Igneous rocks

• Igneous rocks are formed from melted rock that has cooled and solidified. When rocks are buried deep within the Earth, they melt because of the high pressure and temperature; the molten rock (called magma) can then flow upward or even be erupted from a volcano onto the Earth's surface.

• Igneous Rock – Rhyolite

流纹岩

• Sedimentary rocks

Sedimentary rocks are formed at the surface of the Earth, either in water or on land. They are layered accumulations of sediments-fragments of rocks, minerals, or animal or plant material.

• Metamorphic Rocks

Metamorphic rocks are formed when other kinds of rocks are changed by great heat and pressure inside the earth. The word "metamorphic" means changed. Think of metamorphic rocks as recycled rocks. When igneous, sedimentary or even metamorphic rocks get buried deep beneath the surface of the earth, over millions of years the heat and pressure inside the earth change them into something else. Limestone can be changed to marble, sandstone can be changed into quartzite, and shale can be changed to slate. It's just another example of how the earth is constantly changing!

• Metamorphic Rocks – Slate

• Important Term

Andesite :Extrusive igneous rock. Intermediate color; fine grain. Rapid- cooled mineral equivalent of diorite.

• Basalt

Extrusive igneous rock. Dark color; fine grain. Rapid-cooled mineral equivalent of gabbro or diabase.

• Breccia

• Clastic sedimentary rock composed of angular fragments in a binding matrix.

• Chert

Flint-like (glassy) sedimentary rock composed mostly of silica. Chert nodules may be deposited by precipitation of silica in voids left by organic decay.

• Coal

Black or dark brown carbon-righ combustible rock composed of compressed plant remains. Usually sedimentary. When plant and animal matter gets buried under tons of dirt and rocks for millions of years, it is sometimes transformed into coal. Heat and pressure inside the earth turn a type of soft,brown coal called lignite（褐煤） into harder, more useful coals. There are two different types of coal; bituminous and anthracite. Bituminous coal is softer and puts more pollution into the air when it is burned. Anthracite(无烟煤) coal is harder, shinier and burns with less pollution.

• Conglomerate

• Clastic sedimentary rock composed of rounded fragments in a binding matrix.

• Diabase

• Intrusive igneous rock. Dark color; medium grain. Mineral equivalent of gabbro or basalt.

• Diorite

• Intrusive igneous rock. Intermediate color; coarse grain. Slow- cooled mineral equivalent of andesite.

• Dolomite

• Sedimentary rock composed of calcium and magnesium carbonate; usually limestone altered by magnesium-rich brines. Sometimes called "dolostone" to distinguish from mineral dolomite.

• Gabbro

Intrusive igneous rock. Dark color; coarse grain. Slow-cooled mineral equivalent of basalt or diabase.

• Gneiss

• Foliated metamorphic rock composed of light (feldspar, quartz) and dark (biotite, hornblende) mineral layers or lenses. Product of high pressure and temperature.

• Granite

• Intrusive igneous rock. Light color; coarse grain. Slow-cooled mineral equivalent of rhylolite.

• Graywacke

• Clastic sedimentary rock composed of particles of many sizes, poorly sorted and bound in a "dirty" matrix. Thought to be deposited by marine turbidity currents.

• Hornfels

• Non-foliated very-fine-grain metamorphic rock; usually produced by high-temperature contact metamorphism around intrusive bodies.

• Lecture six

• Weathering

• Definition of weathering:

• Breakdown of rock to form sediment

• Introduction of weathering

• is the breakdown and alteration of rocks and minerals at or near the Earth's surface into products that are more in equilibrium with the conditions found in this environment. Most rocks and minerals are formed deep within the Earth's crust where temperatures and pressures differ greatly from the surface. Because the physical and chemical nature of materials formed in the Earth's interior are characteristically in disequilibrium with conditions occurring on the surface. Because of this disequilbrium, these materials are easily attacked, decomposed, and eroded by various chemical and physical surface processes.

• Weathering is the first step for a number of other geomorphic and biogeochemical processes. The products of weathering are a major source of sediments for erosion and deposition. Many types of sedimentary rocks are composed of particles that have been weathered, eroded, transported, and terminally deposited in basins. Weathering also contributes to the formation of soil by providing mineral particles like sand, silt, and clay. Elements and compounds extracted from the rocks and minerals by weathering processes supply nutrients for plant uptake. The fact that the oceans are saline in the result of the release of ion salts from rock and minerals on the continents. Leaching and runoff transport these ions from land to the ocean basins where they accumulate in seawater. In conclusion, weathering is a process that is fundamental to many other aspects of the hydrosphere, lithosphere, and biosphere.

• Types of Weathering

• A. Physical or mechanical weathering

• B. Chemical weathering

• C. Biological weathering

• A. Physical or mechanical weathering

• Frost wedging - water expands when it freezes

• Exfoliation or unloading -

• rock breaks off into leaves or sheets along joints which parallel the ground surface;

• caused by expansion of rock due to uplift and erosion; removal of pressure of deep burial;

• Thermal expansion -

• repeated daily heating and cooling of rock;

• heat causes expansion; cooling causes contraction.

• different minerals expand and contract at different rates causing stresses along mineral boundaries.

• B. Chemical weathering

• Rock reacts with water, gases and solutions (may be acidic); will add or remove elements from minerals.

• Dissolution (or solution) -

• Several common minerals dissolve in water

• halite

• calcite

• Limestone and marble contain calcite and are soluble in acidic water

• Marble tombstones and carvings are particularly susceptible to chemical weathering by dissolution. Note that the urn and tops of ledges are heavily weathered, but the inscriptions are somewhat sheltered and remain legible.

• Photo taken in an above-ground cemetery in New Orleans

• Caves and caverns typically form in limestone

• speleothems are cave formations

• speleothems are made of calcite

• form a rock called travertine(石灰华)

• stalactites - hang from ceiling

• stalagmites - on the ground

• Karst topography forms on limestone terrain and is characterized by:

•

• caves/caverns,

• sinkholes,

• disappearing streams,

• springs

• Oxidation

• Oxygen combines with iron-bearing silicate minerals causing "rusting"

• olivine

• pyroxene

• amphibole

• biotite

• Iron oxides are produced

• limonite

• hematite

• goethite

• Iron oxides are red, orange, or brown in color

• Mafic rocks such as basalt (which may contain olivine, pyroxene, or amphibole) weather by oxidation to an orange color

• Hydrolysis

• Silicate minerals weather by hydrolysis to form CLAY.

• Feldspar alters to clay (kaolinite) plus dissolved materials (ions)

• -Feldspars are stable at high temperatures and pressures (but not at the temperatures and pressures of the Earth's surface)

• -Clays are stable under conditions at the Earth's surface

• -Feldspars and clays are similar in composition.

• -Feldspar readily alters to clay when in contact with acid and water.

• Iron-bearing silicate minerals weather to form clays by hydrolysis (in addition to iron oxides

• Carbonation

• is the reaction of carbonate and bicarbonate ions with minerals. The formation of carbonates usually takes place as a result of other chemical processes. Carbonation is especially active when the reaction environment is abundant with carbon dioxide. The formation of carbonic acid, a product of carbon dioxide and water, is important in the solution of carbonates and the decomposition of mineral surfaces because of its acidic nature.

• Spheroidal weathering is caused by chemical weathering of jointed rocks. The jointed rocks weather to form roughly spherical shapes.

• Brief summary on Chemical Weathering

• The most important factor affecting all of the above mentioned chemical weathering processes is climate. Climatic conditions control the rate of weathering that takes place by regulating the catalysts of moisture and temperature. Experimentation has discovered that tropical weathering rates, where temperature and moisture are at their maximum, are three and a half times higher than rates in temperate environments.

• C. Biological weathering

• Biological weathering involves the disintegration of rock and mineral due to the chemical and/or physical agents of an organism. The types of organisms that can cause weathering range from bacteria to plants to animals.

• Biological weathering involves processes that can be either chemical or physical in character. Some of the more important processes are:

• 1. Simple breaking of particles, by the consumption of soils particles by animals. Particles can also fracture because of animal burrowing or by the pressure put forth by growing roots.

• 2. Movement and mixing of materials. Many large soil organisms cause the movement of soil particles. This movement can introduce the materials to different weathering processes found at distinct locations in the soil profile.

• 3. Simple chemical processes like solution can be enhanced by the carbon dioxide produced by respiration. Carbon dioxide mixing with water forms carbonic acid.

• 4. The complex chemical effects that occur as a result of chelation. Chelation is a biological process where organisms produce organic substances, known as chelates, that have the ability to decompose minerals and rocks by the removal of metallic cations.

• 5. Organisms can influence the moisture regime in soils and therefore enhance weathering. Shade from aerial leaves and stems, the presence of roots masses, and humus all act to increase the availability of water in the soil profile. Water is a necessary component in several physical and chemical weathering processes.

• 6. Organisms can influence the pH of the soil solution. Respiration from plant roots releases carbon dioxide. If the carbon dioxide mixes with water carbonic acid is formed which lowers soil pH.

Cation exchange reactions by which plants absorb nutrients from the soil can also cause pH changes. The absorption processes often involves the exchange of basic cations for hydrogen ions. Generally, the higher the concentration of hydrogen ions the more acidic a soil becomes.

• conclusion

• Weathering is the first step for a number of other geomorphic and biogeochemical processes. The products of weathering are a major source of sediments for erosion and deposition. Many types of sedimentary rocks are composed of particles that have been weathered, eroded, transported, and terminally deposited in basins. Weathering also contributes to the formation of soil by providing mineral particles like sand, silt, and clay. Elements and compounds extracted from the rocks and minerals by weathering processes supply nutrients for plant uptake. The fact that the oceans are saline in the result of the release of ion salts from rock and minerals on the continents. Leaching and runoff transport these ions from land to the ocean basins where they accumulate in seawater. In conclusion, weathering is a process that is fundamental to many other aspects of the hydrosphere, lithosphere, and biosphere.

• End of lecture 4

• unloading

• Exfoliation

• General view of karst topography, St. Paul Group, Chambersburg Limestone. Pennsylvania, north of Clear Spring, MD. Note small closed depressions.

• Tower Karst near Lijiang River,Guilin

• Karst landscape of Guilin

• Karst plain of Longsheng county,Guilin

• Karst spring,Kaiyou village,Kaili County

• Blind fish in cave stream

• Biotite黑云母

• Limonite褐铁矿

• Kaolinite高岭石

• Albite 钠长石

• Sanidine 透长石

• Roots of trees and other plants

• Lichens, fungi, and other micro-organisms

• Lecture 8

• Atmosphere and Climate

• A Atmospheric Composition

•

• What do you know from the table above？

• The table indicates that nitrogen and oxygen are the main components of the atmosphere by volume. Together these two gases make up approximately 99 % of the dry atmosphere.

• The next most abundant gas on the table is water vapor.

• The fifth most abundant gas in the atmosphere is carbon dioxide.

• Water vapor has several very important functional roles on our planet:

• It redistributes heat energy on the Earth through latent heat energy exchange.

• The condensation of water vapor creates precipitaion that falls to the Earth's surface providing needed fresh water for plants and animals.

• It helps warm the Earth's atmosphere through the greenhouse effect.

• carbon dioxide

• The volume of this gas has increased by over 25 % in the last three hundred years. This increase is primarily due to human induced burning for fossil fuels, deforestation, and other forms of land-use change. Some scientists believe that this increase is causing global warming through an enhancement of the greenhouse effect. Carbon dioxide is also exchanged between the atmosphere and life through the processes of photosynthesis and respiration.

• B. The Layered Atmosphere

•

According to temperature, the atmosphere contains four different layers.

The first layer is called the troposphere.

Above the tropopause is the stratosphere.

Separating the mesosphere from the stratosphere is transition zone called the stratopause

The last atmospheric layer has an altitude greater than 80 kilometers and is called the thermosphere.

• C. Earth's Climatic History

• Reconstructing Past Climates

• Earth's Climatic History

• Reconstructing Past Climates

• meteorological instrument records.

• Written documentation and descriptive accounts

• proxy data

The depth of this layer varies from about 8 to 16 kilometers. About 80 % of the total mass of the atmosphere is contained in troposphere. It is also layer where the majority of our weather occurs . Maximum air temperature also occurs near the Earth's surface in this layer. With increasing height, air temperature drops uniformly with altitude at a rate of approximately 6.5° Celsius per 1000 meters. This phenomenon is commonly called the Environmental Lapse Rate. At an average temperature of -56.5° Celsius, the top of the troposphere is reached. At the upper edge of the troposphere is a narrow transition zone known as the tropopause.

This layer extends from an average altitude of 11 to 50 kilometers above the Earth's surface. The lower portion of the stratosphere is also infuenced by the polar jet stream and subtropical jet stream. In the first 9 kilometers of the stratosphere, temperature remains constant with height. A zone with constant temperature in the atmosphere is called an isothermal layer. From an altitude of 20 to 50 kilometers, temperature increases with an increase in altitude.

In the mesosphere, the atmosphere reaches its coldest temperatures (about -90° Celsius) at a height of approximately 80 kilometers. At the top of the mesosphere is another transition zone known as the

mesopause.

Temperatures in this layer can be as high as 1200° C. These high temperatures are generated from the absorption of intense solar radiation by oxygen molecules (O2).

• Common climatic elements measured by instruments include temperature, precipitation, wind speed, wind direction, and atmospheric pressure.

• Written documentation and descriptive accounts of the weather make up the second general category of evidence for determining climate change. Weather phenomena commonly described in this type of data includes the prevailing character of the seasons of individual years, reports of floods, droughts, great frosts, periods of bitter cold, and heavy snowfalls. Large problems exist in the interpretation of this data because of its subjective nature.

• Some common examples of proxy data include: Glacial Ice Deposits， Biological Marine Sediments，Inorganic Marine Sediments ，Terrestrial Geomorphology and Geology Proxy Data ，Terrestial Biology Proxy Data

• Earth's Climatic History

• The period from 2,000,000 - 14,000 B.P. (before present) is known as the Pleistocene or Ice Age.

• The most recent glacial retreat is the Holocene epoch .

• The warming was shortly interrupted by a sudden cooling, known as the Younger-Dryas, at about 10,000 - 8500 BC . Holocene and were 1 to 2° Celsius warmer than they are today. Climatologists call this period the Climatic Optimum.

• Earth's Climatic History

• From 3000 to 2000 BC a cooling trend occurred.

• The period from 750 BC - 900 AD saw warming up to 150 BC.

• The period 900 - 1200 AD has been called the Little Climatic Optimum.

• From 1550 to 1850 AD global temperatures were at their coldest since the beginning of the Holocene. Scientists call this period the Little Ice Age.

• The period 1850 to present is one of general warming .

• Figure 7C-1: Near-global annual-mean temperature change for the period 1880 to 1999 (deviation from the normal period 1951-1980). (Source: NASA Goddard Institute for Space Studies - Global Temperature Trends).

• Figure 7c-2: In 1999, most parts of the world were warmer than normal. The illustration above describes the annual temperature deviation (from the base period 1950-1980) in degrees Celsius for the Earth's surface. The illustration indicates that it was particularly warm across most of North America, northern Africa, and most of Eurasia. The tropical Pacific Ocean was cool due to a strong La Nina. (Source: NASA Goddard Institute for Space Studies - Global Temperature Trends).

• D. Causes of Climate Change

• Causes of Climate Change

• Variations in the Earth's Orbital Characteristics.

• Atmospheric Carbon Dioxide Variations.

• Volcanic Eruptions.

• Variations in Solar Output.

• Figure 7d-2: Modification of the timing of aphelion and perihelion over time (A = today; B = 13,000 years into the future).

• Figure 7d-3: The following graph illustrates the rise in atmospheric carbon dioxide from 1744 to 2005. Note that the increase in carbon dioxide's concentration in the atmosphere has been exponential during the period examined. An extrapolation into the immediate future would suggest continued increases.

• Figure 7d-4: Explosive volcanic eruptions have been shown to have a short-term cooling effect on the atmosphere if they eject large quantities of sulfur dioxide into the stratosphere. This image shows the eruption of Mount St. Helens on May 18, 1980 which had a local effect on climate because of ash reducing the reception of solar radiation on the Earth's surface. Mount St. Helens had very minimal global effect on the climate because the eruption occurred at an oblique angle putting little sulfur dioxide into the stratosphere. (Source: U.S. Geological Survey, photograph by Austin Post).

• Figure 7d-5: Ash column generated by the eruption of Mount Pinatubo on June 12, 1991. The strongest eruption of Mount Pinatubo occurred three days later on June 15, 1991. (Source: US Geological Survey).

• Figure 7e-7: The sun as seen at sunset. The sun is essentially the only source of energy for running the Earth's climate. Thus any change in its output will result in changes in the reception of insolation and the generation of heat energy which drives the climate system.

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