c) note down the three most widely used models to describe the earths shape.
Part C. After Listening Activities
Task 1. Discuss in pairs.
1. What is the equatorial bulge?
2. Are all three models only approximations?
Task 2. Summarize the information about the different ways of describing the earths shape (in writing).
Revision
Ex. 1. Fill in the text with the appropriate word from the box.
| ice age, took place, inhabitants, era, dates, human, cooled, liquid, primitive, rain, organisms, hemisphere, stages, forms, animal, earths, oxygen, species, evolved, crust, appeared, spread, dry, complex, moved, existence |
History of the Earth
Although it is difficult to say anything definite about events that (1) _____ (2) _____ so long ago, scientists have been able to suggest some (3) _____ from the main (3) _____ in the history of our planet. 5,000 million years ago, they tell us, the earth came into (4) _____ as a mass of (5) _____ fire. About a thousand million years later the crust (6) _____ and hardened and seas were formed by (7) _____. After about another thousand million years bacterialike cells (8) _____ in the seas. One of the earliest life forms to develop, about 2,000 million years ago, was algae, and they produced (8) _____. Now that there was oxygen in the atmosphere, conditions were suitable for the development of more (9) _____ life forms. At first single-cell, and later, multicellular, (10) _____ appeared.
Meanwhile the (11) _____ of the earth was continually contracting and shifting and between 600 and 225 million years ago (12) _____ land gradually emerged. Some living forms then (13) _____ to the land and in time amphibians, insects and reptiles evolved.
At the same time forests and ferns (14) _____ over the land. Living (15) _____ then proceeded to flourish and multiply and many new (16) _____ evolved. About 223 million years ago flowering plants first (17) _____ on earth. This (18) _____ life for millions of years. Some 75 million years later the first mammals and birdlike creatures evolved.
About the next stage in the earths history more is known, thanks to the abundance of fossils from this biological clan to which (19) _____ beings belong, have been the dominant form of animal life. The first (20) _____ ape appeared about 40 million years ago and was followed by a manlike ape around 10 million years later. About a million years ago the (21) _____ landscapes were changed by the movements of snow and ice over the Northern (22) _____. This period is known as the (23) _____ (24) ____ when the climate became warmer again about half a million years ago, the first human beings appeared. Humans are thus among the most recently arrived (25) _____ of the earth.
Ex. 2. Translate the text into Russian (in writing).
Latitude and Longitude
Locations on the earth's surface are specified in terms of the earth's axis of rotation. A great circle is any circle on the earth's surface whose center is the earth's center. The equator is a great circle midway between the North and South Poles. A meridian is a great circle that passes through both poles, and it forms a right angle with the equator. The prime meridian passes through Greenwich, England. The longitude of a point on the earth's surface is the angular distance between a meridian through this point and the prime meridian; the prime meridian is assigned the longitude 0, and longitudes are given in degrees east or west of the prime meridian. Thus a longitude of 60W identifies a meridian 60 west of the prime meridian.
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The latitude of a point on the earth's surface is the angle between a line from the earth's center to it and another line drawn from the center to a point on the equator on the same meridian. Thus the latitude of the North Pole is 90N, that of the South Pole is 90S, and that of the equator itself is just 0. A latitude of 60N identifies a circle 60 north of the equator. Degrees of latitude and longitude are further divided into minutes [1 = 60 minutes (60')], and minutes are further divided into seconds [1' = 60 seconds (60')]. A nautical mile is equal to a minute of latitude, and is 6,080 ft in length. (A statute mile, used on land, is 5,280 ft in length.) Because of the way they are defined, parallels of latitude are equally spaced everywhere (hence the usefulness of the nautical mile), but meridians of longitude converge at the poles.
On December 22, the shortest day of the year in the Northern Hemisphere, the 23.5 tilt of the earth's axis means that no sunlight reaches any point within 23.5 from the North Pole. The Arctic Circle is the boundary of this region of darkness. On the same day, which is the longest day of the year in the Southern Hemisphere, there are 24 h of daylight at all points within 23.5 of the South Pole, and the Antarctic Circle is the boundary of this region of daylight. On June 22 the situations in the two hemispheres are reversed.
The Tropic of Cancer is the most northerly latitude in the Northern Hemisphere at which the sun is ever directly overhead at noon. The Tropic of Capricorn is corresponding latitude in the Southern Hemisphere. On June 22, when the North Pole is titled closest to the Sun and which is hence the day of maximum sunlight in the Northern Hemisphere, the noon sun is directly overhead 23.5 º north of the equator; hence the latitude of the Tropic of Cancer is 23.5º N. Similarly the latitude of the Tropic of Capricorn is 23.5 º S; the South Pole is tilted closest to the sun on December 22, when the noon sun is directly overhead at this latitude.
Ex. 3. Find the terms in the text which describe the following:
1. The name of the meridian which passes through Greenwich.
2. A great circle that is drawn midway between the North Pole and the South Pole.
3. The name of the most southerly latitude above which the sun is directly overhead at 12 noon.
4. The name of that latitudes equivalent in the Northern Hemisphere.
5. The point that has a latitude of 900 N.
6. The point that has a latitude of 900 S.
7. A mile that is used on land.
8. Any circle on the earths surface whose centre is the earths centre.
Ex. 4. These words can all be explained in simpler, more everyday language. Can you do that?
1. location
2. rotation
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3. assign
4. further
Ex. 5. Imagine you do not understand the following terms. Ask each other for an explanation.
1. Tropic of Cancer
2. Tropic of Capricorn
3. South Pole
4. North Pole
5. Equator
Ex.6. Translate the text into English using the vocabulary of the Unit.
| . . , , , . , , VI . . . . , . . . , , . , , . | it took much effort the idea edge eclipse rounded |
Active Vocabulary
boundary n
boring n , ,
constitute v ,
core n
cover v ,
cover n
density n
earthquake n
enclose n
eruption n (, )
exist v
folding n
fossil n ,
moist a
molten a
with reference to ,
rock n
sediment n
solid a
vast a ,
Additional Reading
Yellowstone National Park
Yellowstone National Park is very famous to many people Yellowstone means Yogi Bear. The more enlightened might think of grizzly bears, bison and the wolves that have been reintroduced to the park in recent years. Yellowstone is famous for its wildlife and has much importance as the core of the Greater Yellowstone ecosystem.
Yellowstone is also well known for its geysers, hot springs and other impressive hydrothermal features. Few people are aware that these are caused by a gigantic magma chamber. Which in some places is only 3 km beneath the surface [remember that continental crust is on average 30 km thick]. Even fewer would think of Yellowstone as a massive volcanic system, with much of the park located inside an enormous caldera. Yellowstone is, in fact, a super volcano that has produced some of the biggest and most powerful eruptions ever to affect the planet. A future eruption could cause devastation on a scale far beyond that of any volcanic disaster in recorded history.
Yellowstone National Park covers 8,987 km2, mostly in the northwest corner of the state of Wyoming, but also extending into Montana to the north and west and Idaho to the southwest. Most of the park is a plateau with altitudes ranging around 2,000 m above sea level. Outside the central area, the park is bounded by taller mountain ranges that are part of the Rocky Mountain chain. The Absaroka Range, with peaks over 3,000 m, lines the eastern side of the park, and the Gallatin Range is to the north-west.
Founded in 1872, Yellowstone was the world's first national park. In the early nineteenth century, several fur trappers visited the Yellowstone area, returning back east with bizarre tales of a land of 'fire and brimstone' where 'waterfalls spout upwards'. After the American Civil War, expeditions were sent into the area to find out whether there was any truth to these tales. One of the most important of these was the Hayden expedition of 1871 mounted by the United States Geological Survey (USGS). This expedition mapped and studied many of the hydrothermal phenomena in the area, establishing Yellowstone's geological importance.
Some of Yellowstone's fantastic scenery became widely recognised because of the landscapes painted by Thomas Moran who accompanied the Hayden expedition. All of this generated much public interest, and there was a real danger of the area becoming damaged by development and souvenir hunting. Realising that few of the geysers and hot springs would survive in their natural state without protection, in 1872 the US government took what was then a radical step, authorising the establishment of a national park for 'the benefit and enjoyment of the people'. It became the inspiration other national parks all over the world.
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The geological setting
It is only since the 1960s that Yellowstone's geology and volcanic history have been fully appreciated. In addition to mapping various solidified lava flows, geologists from the USGS (United States Geological Survey) have identified three distinct welded tuff deposits that extend over thousands of square kilometres both within and outside the park. This discovery is significant because tuff is formed only from highly explosive volcanic eruptions. Furthermore, the enormous volume of tuff that has been deposited provides evidence for past eruptions on a truly colossal scale.
The discovery of these deposits (collectively known as the Yellowstone group of tuffs) created a new question. How could such a huge amount of ash and lava have been produced when there was no obvious volcano to be seen in the park? The answer eluded (, ) geologists until it was realised that the central area of Yellowstone National Park actually sits inside an enormous caldera, 72 km long by 48 km wide. From the ground there isn't a volcano or caldera in sight, but this is because it is so big that you are inside it! The full scale and outline of this caldera can only be appreciated from the air. Calderas are formed by the eruption of large bodies of magma through the crust.
Measurement of seismic waves travelling beneath the caldera has shown that they slow down significantly around 3 km beneath the ground. This indicates that there is a lot of molten magma, rather than just solid rock, at relatively shallow depths within the crust. Detailed seismic surveys have made it possible to estimate the dimensions of this body of magma. It is approximately 48 km long, 19 km wide and 10 km thick. The relatively low density of this molten material compared with solid rock also accounts for the lower than normal gravity values that are measured across the Yellowstone Plateau.
Like Hawaii, Yellowstone is far from any plate margin and therefore its volcanism must be explained by a hot spot. As at Hawaii (perhaps the best known hot spot), geologists believe that a plume of mantle is rising upwards from the asthenosphere, continually injecting magma into the lithosphere beneath Yellowstone.
No one knows exactly why mantle plumes occur where they do, but their existence in some places rather than others must relate to irregularities in the output of heat from around the Earth's core. Although both Hawaii and Yellowstone are located over hot spots, Hawaii is on oceanic crust while Yellowstone is on continental crust. This is the reason why the type of volcanism experienced in the two areas is so different.
Those who have studied volcanoes in Hawaii, such as Mauna Loa and Kilauea, will know that these are classic examples of shield volcanoes that frequently emit hot, runny basaltic lava in predominantly nonviolent eruptions. Yellowstone eruptions, on the other hand, are extremely rare but incredibly explosive. Yellowstone provides an excellent example of a hot spot under continental crust.
Hydrothermal features
Yellowstone contains a great variety of strange and wonderful hydrothermal features including geysers, hot springs, fumaroles, mudpots and mud volcanoes. Of these, geysers are the most impressive, and no trip to the park is complete without a visit to Old Faithful, Yellowstone's most reliable geyser. It is not the largest of Yellowstone's geysers, but it does erupt to heights over 30 m every 80 minutes or so giving tourists a guaranteed photo opportunity. There are other smaller geysers that erupt more frequently, and some larger geysers that only erupt once every several days.
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There are more geysers at Yellowstone (over 500, located in seven geyser basins) than in all the other hydrothermal regions of the world put together. Geysers are so abundant in Yellowstone because of a combination of plenty of precipitation, porous, fractured rocks and a heat source from the body of magma beneath. When water from rainfall or melting snow percolates deep enough into the bedrock, it becomes so hot that it is forced back upwards through cracks and joints in the rock. In some places the rising hot water fills a void in the rock (a chamber) with a constricted opening to the surface.
In these places the rising water fills the chamber more quickly than it can escape upwards, eventually causing the pressure to build up to such an extent that superheated water explodes into steam, blasting upwards through the constricted passage to the surface as a geyser eruption. After the geyser has erupted, it remains dormant until the underground chamber has refilled and the critical pressure is again reached.
The size and frequency of geyser eruptions depend upon many factors including the size and configuration of the chamber, the rate of water movement through the rock, and the size and length of fractures in the rock that connect chambers with each other and with the surface. All of this can be thought of as the underground 'plumbing' of a geyser. Like Old Faithful, some geysers are remarkably regular, but it only takes a minor earthquake to shift the underground plumbing and change their character and timing. The geyser basins of Yellowstone are dynamic, ever adjusting to movements in the crust that cause some geysers to go extinct while new ones are born.
Hot springs are far more common than geysers occurring wherever heated ground-water rises gently to the surface. Points where only steam reaches the surface are called fumaroles. The hot springs of Yellowstone are highly varied in size, temperature and colour. The colours depend on differences in the temperature and chemical composition of the water and the presence of species of algae and bacteria adapted to those conditions.
A hot spring can also be distinctive for the rim of mineral deposits that builds up around it. As the rising groundwater spills out over the surface, silica in solution precipitates to form whitish deposits of sinter. This not only forms the rim of pools but can build up into mounds or cones where geysers erupt, and can form large, whitish expanses as at Porcelain Basin. In areas of Yellowstone underlain by limestone, such as at Mammoth Hot Springs, travertine rather than sinter is deposited around the springs.
In some parts of Yellowstone the ground-water is very acidic due to hydrogen sulphide gas from the crust mixing with water and being metabolised by bacteria to produce sulphuric acid. One of the most acidic springs in the park is Sulphur Caldron. Here the water has a pH of just 1.2 and a foul, sulphurous smell of rotten eggs. It is not a place where tourists linger long! In such areas, silica compounds stay in solution and there is no deposition of sinter. Instead, surrounding rocks are chemically weathered into clays, and where the hot, acidic ground-water rises to the surface it often forms viscous, bubbling pools of mud known as mudpots. Sometimes the mud can pile up into a cone as at Mud Volcano, only to be blown away in a muddy eruption once there is enough steam pressure.
UNIT V
| THE ATMOSPHERE |
Reading Material
Text A
Task
