Grade 11 Geography Past Paper PDF

Geo-spatial Climate Formationinformation Classification of Earth’s and data...

Geo-spatial Climate Formationinformation Classification of Earth’s and data and Regions Continentsprocessing of the World UNIT ONE At the end of this unit, you will be able to: recognize the Earth’s geological history; describe the formation of the Earth’s Continents; explain the relative distribution of Continents and Oceans overthe Globe; and appreciate the changing positions of the Earth’s Continents and Oceans over geological times. Main Contents : 1.1. Formation of the continents and oceans 1.2. Geological timescale 1.3. Distribution of the continents and cceans 1.4. Changing positions of the continents and oceans Introduction Students, do you remember the lessons on ‘Geological History of Ethiopia’ and ‘Landforms of Africa’ in your Grade Nine and Ten Geography, respectively? If yes, can you tell us what geological history is and how the landforms of Africa have been developing? In unit one of Grade 11 Geography you are going to learn about the timescale of the Earth’s geological processes; the development stages of the earth’s continents; and the relative position (distribution) of the Earth’s oceans and continental landmasses. With these basic contents you are; therefore, expected to be aware of and appreciate the Earth’s geologic timescales, formation of the continents, and relative position/distribution of the Earth’s oceans and continental landmasses. UNITUNIT TWO ONE 1.1. FORMATION OF CONTINENTS This section presents how the Earth and continents evolved. The topic takes you to the wider scientific wisdom of the origin of the Earth and its Continents. At the end of this section, you will be able to: examine how the Earth was created; and describe how the Earth’s continents evolved. Keywords: Big bang Pangaea Continents Rodinia Continental drift Sea-floor spreading mid-oceanic Solar system Brainstorming Activity 1.1 Please attempt the following questions first individually and then in groups: 1. Do you know how the Earth was formed or created? 2. What do you imagine about the formation of the Earth and Continents? The Earth, together with other planets and their moons, form the planetary system. The Sun and the planets together again form the Solar System (Sun System; see Figure 1.1). The formation of the Earth is thus attributed similar to the creation of other companion planets and the entire development of the Solar System. Therefore, it is necessary to comprehend the origin of the Solar System to understand the foundation of the Earth. As can be learned from Earth Science literature, there are different views and theories on the formation of the Earth and that of the Solar System. However, most of the theories depend on speculation and ambiguous assumptions. None of them are capable of acceptably demonstrating all the ultimate features of the Earth and the Solar System.  Geo-spatial Climate Formationinformation Classification of Earth’s and data and Regions Continentsprocessing of the World Among the various assumptions and theories proposed about the formation of the Universe and Earth, the “Big Bang” is most widely supported by scientists. According to this theory, the Universe originated sometime 10–20 billion years ago by an abrupt cosmic explosion initiated by the expansion of a small volume of matter at an exceedingly high density and temperature. This space explosion was then followed by the formation of numerous space objects like the Sun, planets (Figure 1.1), stars, meteors, asteroids, and comets through material collision, cooling, and gravitational attraction. Our Earth was thus created from the mixture of gas and dust particles moving in space around the Sun about 4.5 billion years ago. Figure 1.1 The Solar System (Sun & Planets) [Wicander & Monroe, 2010] Brainstorming Activity 1.2 Discuss the questions below with your classmates and teacher: 1. How were the continents formed/created? 2. How did the present-day continents come into being? 3. How were they separated from the Pangaea? 4. What is continental drift? How does it happen? The first cosmic rocks solidified and created the first Earth at about 4600 to 3900 Ma. Fol- lowing that, initial land masses gathered to form the early continent called ‘Rodinia’ (Figure 1.2). UNITUNIT TWO ONE Figure 1.2 Neoproterozoic Supercontinent; Rodinia at about 750 Ma (Wicander & Monroe, 2010) During the late Cambrian period (514 Ma) the Gondwana Supercontinent had evolved around the South Pole. Next to this four major continents (Gondwana, Baltica, Siberia & Laurasia) came into being during 458 Ma (in the mid-Ordovician Period). Then the Laurasia continent collided with the Baltica and closed the Iapetus Sea during the mid-Silurian (425 Ma). The continual collision had then produced the pre-Pangaea continent during the early Devonian period, at about 390 Ma. At about 306 Ma (in the late Carboniferous period) the North American continent started to develop from the assemblage of rocks. By then, the Supercontinent (Pangaea) had come into being at about 255 -210 Ma. From 210 -180 Ma (in the Triassic period) this Supercontinent started to break apart. The break-up had continued until the late Cretaceous. In the meantime, North America had moved away from the African continent. During the late Cretaceous, the breaking-apart of Pangaea widened and bigger water masses (Oceans) were created along the continental cracks. Finally, continental break-up progressively continued during the Tertiary period; the Earth’s continents have then retained their present position during the Quaternary (Figure 1.3).  Geo-spatial Climate Formationinformation Classification of Earth’s and data and Regions Continentsprocessing of the World Figure 1.3 Continents at different Geological times (Gabler et al., 2007) Tip: An additional information is available online for you at: https://www.youtube.com/watch?v=6-vHe4599NE From the preceding section, it is possible to note that the present-day continents were joined together by forming Pangaea until about 200 Ma. At about 160 Ma, Pangaea divided into two bigger landmasses called Gondwanaland and Laurasia by the process of continental drift. The landmass that developed into sub-continent India moved northwards and separated from the Gondwana continent at about 140 Ma. This occasion caused the collision of the Indian sub-continent with Eurasia and initiated the formation of the Himalayas ranges. Some 100 Ma, Australia had separated from Antarctica and this has pronounced the break-up of the Gondwana continent. The two giant continents (Gondwanaland & Laurasia), then moved- apart east and west thereby resulting in the opening of the Atlantic Ocean. UNITUNIT TWO ONE NOTE Continental drift refers to the moving apart of conti- nents initiated by Sea-floor Spreading at mid-Ocean- ridge locations. The event makes the Pacific Ocean narrower, the Atlantic Ocean wider, the Mediterra- nean Sea narrower, and the Himalayan Mountains higher. The drift makes Australia reach the equator in 60 million years. Please answer the following questions: 1. Explain how the Earth’s continents were created? 2. Name the two Supercontinents that evolved at about 200 Ma. 3. What is Pangaea?  Geo-spatial Climate Formationinformation Classification of Earth’s and data and Regions Continentsprocessing of the World This topic focuses on the geological history of the Earth as condensed in the geological time- cale, mainly on the major Earth forming processes, resultant landforms, and the successions of interrelated life-forms. At the end of this unit, you will be able to: use the geological timescale for the explanation of the geological processes, re- sultant features, and associated life-forms; describe the difference between relative and absolute ages of the Earth’s rocks; examine the geological eras of the earth. Examine the Geological Eras of the Earth. Keywords: Absolute age Half-life Epoch Period Geological era Radioactive Geological timescale decay Isotope Relative age Brainstorming Activity 1.3 Please organize yourself into groups and attempt the following ques- tions: 1. Have you ever heard about the geological history of the Earth? 2. What is the geological timescale? 3. How was the age of the Earth established? 4. How do scientists determine the age of the Earth and its products? 1.2.1 Meaning of Geologic Timescale Geological timescale is the time-frame (timetable) showing the possible age of the Earth and its associated life-forms. It provides a review of Earth’s history and the major changes that occurred over time. It is developed by Earth scientists through the study of Earth’s rocks. Through the study of rocks, scientists determine the Relative and Absolute ages of rocks. UNITUNIT TWO ONE 1.2.2. Relative and Absolute Age of Rocks Relative age mainly depends on the analysis of the sequence of geological occurrences without giving due regard to the exact time of origin. It focuses only on determining the sequence of formation of events (whether the event had occurred before or later than the other related one). This method principally depends on the study of sedimentary rocks and often applies to local conditions interpretations. Geologists employ three basic principles (rules) during the study of the relative age of rocks: The principle of original horizontality indicates that layers of sediments are originally placed horizontally under the action of gravity. This means that except for the disturbed sequences, sedimentary rocks are always deposited in nearly horizontal beds. In the hypothetical Figure 1.4a, the rock-layers A, B & C must have been developed in horizontal beds because they have the same orientation. If the beds are no longer horizontal, they must have undergone deformation after formation. The principle of superposition asserts that in an undisturbed sequence of sedimentary rock layers (beds) or lava flows, the overlying bed is younger than the underlying rock. For instance, in Figure 1.4b, the rock layers are placed from earliest (1) to latest (4). Source: www.kean. A) Original Horizontality B) Superposition C) Cross-Cutting Figure 1.4: Sample sedimentary rock-layers The principle of cross-cutting relationships indicates that a rock-layer that cross-cuts another rock-layer is said to be younger than the rocks it cross-cuts. This is a condition where older rocks are cut by younger geologic features or igneous intrusions. In Figure 1.4c, layer 3 is an igneous intrusion created after the formation of the sedimentary layers 1 and 2.  Geo-spatial Climate Formationinformation Classification of Earth’s and data and Regions Continentsprocessing of the World Absolute age refers to the actual age of rocks given in numerical values through the analysis of the spontaneous decay of radioactive isotopes. The term isotope refers to the presence of an element in different forms. Radioactive decay stands for the conversion of unstable (Parent) elements into daughter (Stable) elements through the gaining or losing of particles in their nucleus. For instance, Potassium-40 (40K) decays into Argon-40 (40Ar). Similarly, Carbon-14 (14C) changes to Nitrogen (14N). Rubidium-87 (87Rb) converts also to Strontium-87 (87St). Likewise, Uranium-235 (235U) change to and Lead-207(207Pb) (Table1.1). Table 1.1 Parent and Daughter isotopes and time-taken (half-life) for conversion No Parent isotope Daughter isotope Half-life 1 Uranium - 238 (238U) Lead – 206 (206Pb) 4.5 billion years 2 Rubidium – 87 ( Rb) 87 Strontium – 87 48.8 billion years (87Sr) 3 Potassium-40 (40K) Argon – 40 (40Ar) 1.25 billion years 4 Uranium - 235 (235U) Lead – 207 (207Pb) 704 million years 5 Carbon-14 ( C) 14 Nitrogen – 14 ( N) 5,730 years 14 The time taken to convert from parent element to Daughter element is commonly measured in half-lives. The half-life of an isotope is the time taken for half of the parent isotope to change to its product atoms. The relative proportions of the Parent and Daughter isotopes are used to determine the number of half-lives. Before conversion, 100% of the Parent prevails and no daughter product is formed. After one half-life, 50% of the Parent remains while 50% of the atoms are changed to Daughter atoms. After two half-lives, the number of Parent isotopes is again halved (25%) whilst the number of Daughter atoms increases by the same amount (to 75%). For more clarity please see Table 1.2. Table 1.2 Proportion of Parent and Daughter isotopes during radioactive decay No No of half-lives Proportion (% of total isotopes) Parent isotope Daughter isotope 1 0 100 0 2 1 50 50 3 2 25 75 4 3 12.5 87.5 UNITUNIT TWO ONE Radioactive decay occurs when elements recombine to form new minerals during the processes of metamorphism or when magma cools. Radioactive elements found in igneous and metamorphic rocks are commonly used in rock-dating studies. For instance, see some of the rocks used for dating purposes in Figures 1.5 & 1.6. As mentioned earlier, the geological timescale forms a division of geological processes and life-forms based on standard time units through the study of fossil remains imprinted in rock layers. The scale divides the age of the Earth into Eons, Eras, Periods, and Epochs (Table 1.3). When the geological timescale was initially developed, the earliest fossils were found not exceeding 600 million years (Ma) from the present (the Cambrian Period) in age. Based on that, the part of the geological history of the earth before the Cambrian Period (the time from 600-4500 Ma) is classified as Precambrian. Precambrian, thus, means the time before Cambrian. Uraninite Zircon Hornblende Glauconite a) Sample rocks used in radiometric Trilobite fossil Ammonite fossil Crinoid fossil (Cambrian) (Jurassic) (Carboniferous) b) Some index fossils used in geological Figure 1.5 Sample rocks and index fossils used for geological dating purposes (a,b) Figure 1.6 Radiocarbon  Geo-spatial Climate Formationinformation Classification of Earth’s and data and Regions Continentsprocessing of the World Table 1.3 Geological timescale EON PERIOD EPOCH AGE MAJOR (Ma)* EVENTS C QUATERNARY Holocene Present – Modern Humans E 0.01 N Pleisto- 0.01 – 1.6 Ice Age O cene Z P O T NEOGENE Pliocene 1.6 – 5.3 Early Whominids I E Miocene 5.3 – 23.7 H C R T PALEOGENE Oligo- 23.7 – I cene 36.6 A A Eocene 36.6 – Extinction of R 57.8 Dinosaurs N Y Paleo- 57.8 – 70 cene E M CRETACEOUS 70 - 144 First birds R E JURASSIC 144 - 208 S O TRIASSIC 208 - 250 Start of Pangaea O Z break-up; First O mammals; First Z I Dinosaurs C O P PERMIAN 250 - 286 A PENNSYLVA- 286 - 320 Coal deposits, I L NIAN First Reptiles E O MISSISSIPPIAN 320 -360 C Z DEVONIAN 360 - 408 First Amphibians O I SILURIAN 408 - 438 First land animals; C First land plants; ORDOVICIAN 438 - 505 First Fish CAMBRIAN 505 - 600 First shelled animals PROTERO- P 600 - Formation of the ZOIC R 2500 oldest known E rocks and solid- C ification of the A earth ARCHEAN M 2500 - B 3900 R HADEAN I 3900 - A 4500 N *Ma: Million years Crawford (1998); Wicander & Monroe (2010); www.kean.edu UNITUNIT TWO ONE Based on the geological timescale, the history of the formation of the Earth is classified into four longer geological periods named Eons. Hadean, Archean, Proterozoic, and Phanerozoic are four major sub-divisions of the known Eons. The Hadean, Archean and Proterozoic Eons are often called Precambrian by scientists to refer to the geological time before the emergence of life on Earth. The Phanerozoic is the most recent Eon. It is further sub-broken into three Geological Eras named Paleozoic, Mesozoic, and Cenozoic (see Table 1.3). 1.2. 3.Geologic Eras As can be learned from Table 1.3, four known Geological eras are identified in the history of the Earth. They are the Precambrian, Paleozoic, Mesozoic, and Cenozoic. The Precambrian is the oldest of all the geological eras. It covers the time from 600 million to 4.5 billion years (about 85% of the geological time of the Earth). It was the time of solidification of the Earth and the formation of the oldest rocks. Rocks created during that time are rich in base metallic minerals and are often called crystalline basement complex rocks. Figure 1.7 indcate that they are often found along with the continental Shields or Cratons (landscapes resisted long period of erosion) The Hadean Eon of the Precambrian covers the time 4600 – 3900 Ma and not much is known about it. Archean is the other Eon covering some 1400 (3900 – 2500 Ma). The latest of the three Eons is the Proterozoic lasting from 2500–570 Ma. Figure 1.7 Distribution of Precambrian rocks (shields) [Wicander & Mon-  Geo-spatial Climate Formationinformation Classification of Earth’s and data and Regions Continentsprocessing of the World Figure1.8: Life forms evolved during the different geological eras (Crawford, 1998) UNITUNIT TWO ONE The Paleozoic era covered the time from 600 to 250 Ma from the present. It is believed that it marked the beginning of life and is commonly referred to as the age of ancient life. Trilobites and shelled animals (see Figure 1.8) were the common species of the time. The Devonian, the fourth period of the Paleozoic, was rich in fish species and referred to as the age of fish. By the end of the Paleozoic, all continents of the Earth had joined together and created the Supercontinent named Pangaea (Figure 1.9). The creation of Pangaea led to extreme seasonal weather changes that caused the great extinction of Earth species. Due to that, around 75% of the Amphibian species have perished. Figure 1.9 The Supercontinent (Pangaea) (Gabler et al., 2007) The Mesozoic era marked the time from 250-70 Ma. It is often referred to as the era of middle life and the age of Dinosaurs owing to their relative dominance. Turtles, snakes, crocodiles, and lizards were among the life forms of the time. Low-lying areas were occasionally flooded by shallow marine transgressions followed by depositions of red sandstones and mudstones. Tropical areas were dominated by extensive swamps which later became rich coal deposits. The mid-Mesozoic era was experiencing the splitting of Pangaea into Laurasia and Gondwanaland (Figure 1.9). Igneous activities had initiated also the development of volcanic mountain ranges in western North America. The end of the Mesozoic era saw the emergence of land mammals but marked the mass extinction of Dinosaurs (see Figure 1.8). The Cenozoic era is the recent one covering the time since 70 Ma. As it forms the recent geologic time, it is well known compared to the other Geological eras. Birds, mammals, and flowering plants dominante succeeded on Earth. It is commonly named an era of recent life and the age of mammals.  Geo-spatial Climate Formationinformation Classification of Earth’s and data and Regions Continentsprocessing of the World During the beginning of the Cenozoic era the the rifting of Pangaea has been fully achieved and the continents retained their present form. Great volcanism and orogenic folding caused the formation of numerous volcanic, fault-block, and fold mountains in the different parts of the Earth’s continents. Glaciations were experienced in some high-latitude areas while heavy rainfall occurred in other localities. Extinction of some mammals happened in some localities. Orogenic is the formation of mountains, espe- cially through the folding of the earth’s crust Please organize yourself into groups and answer the following questions: 1. How is the geological timescale es- tablished? 2. What are geological eras? 3. Could you please name some of the life forms that evolved in the differ- ent geological eras? 4. Prepare a geologic timescale chart using graph paper. UNITUNIT TWO ONE This topic of unit one is about the relative size and distribution of the Continental landmasses and Oceanic basins over the Globe. At the end of this section, you will be able to: compare the sizes of landmasses and oceanic basins over the globe; and locate the current positions of Continents and Oceanic basins. Brainstorming Activity 1.4 1. How do you explain the distribution of Con- tinents and Oceans over the Globe? 2. Show the location of the world’s Continents and Oceans using sketch maps? Please study the maps from your textbook and tell the an- swer to your teacher. The surface area of the Earth is estimated to be 510,072,000 km2 and the area of the Oceans is about 363, 000,000 km2. All water (hydrosphere) in total covers greater than 71% of Earth’s surface. The largest of these are the Oceans, which account for over 97% of all the water on Earth. Glaciers and polar ice caps contain just greater than 2% of the Earth’s water in the form of solid ice. Only about 0.6% is found under the surface as groundwater. Nevertheless, groundwater is 36 times more plentiful than water found in lakes, inland Seas, rivers, and in the atmosphere as water vapor. The distribution of Ocean basins and Continents is unevenly arranged over the Earth’s surface (see Figure 1.10). In the Northern Hemisphere, the ratio of land to ocean is about 1:1.5. But it is 1:4 in the Southern Hemisphere. The greater abundance of water in the Southern Hemisphere has some interesting effects on the environment of that area. For example, the climate tends to be more moderate in the Southern Hemisphere because of the ocean’s ability to release large amounts of stored heat energy. The Continents A continent is a huge area of land mostly separate by a water body. There are seven known continents on the earth today. They are: Africa, Antarctica, Asia, Australia, Europe, North America, and South America. A brief description of the continents is presented as follows:  Geo-spatial Climate Formationinformation Classification of Earth’s and data and Regions Continentsprocessing of the World Africa Africa is the second largest continent in the world next to Asia. The equator divides Africa into two parts. But the largest part of the continent is found north of the equator. Africa is the only continent in the world crossed by the equator, Tropic of Cancer, and Tropic of Capricorn. The world’s largest hot desert (Sahara), and the world’s longest river (River Nile),are found in Africa. Africa has 54 countries. Antarctica Antarctica is a permanently ice covered continent located around the South-Pole. The climate is very cold and there are no permanent human settlements in Antarctica. But, many countries have research stations in Antarctica. It is the third smallest continent on the earth. Asia Asia is the largest continent in the world. It lies in the eastern hemisphere covering one-third of the total land area of the earth. It is crossed by the Tropic of Cancer and separated by the Ural Mountains from Europe. It is part of the Eurasia and crossed by the Arctic Circle at its northern margin. It is bounded by water bodies on three sides and by the Pacific Ocean in the east and southern part. Asia has 48 countries and accommodates two-third of the world population. It has the highest mountains (Himalayas), the deepest depressions (Dead Sea), the driest desert (Lut desert), highest precipitation (Assam) and long tradition of civilization (Mesopotamia). Australia Australia is the smallest continent in the world. It is surrounded by water in all of its sides and often called an Island continent or Oceania; and has the largest area of ocean jurisdiction of any country on Earth. It is the driest inhabited continent in the world with 70 percent of it either arid or semi-arid. The vast majority of its population is concentrated along the eastern and south-eastern coasts. Australia entirely lies in the southern hemisphere. Europe Europe is the second smallest continent in the world, and home of the industrial revolution. It has 44 countries. It lies to the west of Asia and north of Africa. Europe is crossed by the Arctic Circle. It is bounded by the Atlantic and Arctic oceans and by the Mediterranean Sea in the south. UNITUNIT TWO ONE North America North America is located to the west of the Atlantic Ocean and linked to South America by the narrow strip of land called the Isthmus of Panama. It is the third largest continent of the earth. It lies north of the equator in the western hemisphere and surrounded by the Atlantic, Pacific and Arctic Oceans. The main countries are three (USA, Canada & Mexico). South America South America is also located in the western hemisphere, but most of its area lies south of the equator. It is bounded in the east by the Atlantic Ocean and in the west by the Pacific Ocean. The world’s largest River (Amazon River), largest and most bio-diverse rainforest, tallest uninterrupted waterfall (Angel Falls) and the north-south extending longest mountain (Andes Mt.) are found in South America. South America has 12 countries. The Arctic Ocean is the world’s smallest Ocean with an area of 14,056,000 km2. It lies in the area between Europe, Asia, and North America. Most of its waters are north of the Arctic Circle. Its average depth is 1,205 m. The deepest point lies at the Nansen Basin or Central Basin and it is –4,665 m deep. Throughout most of the year, much of the Arctic Ocean is covered by a drifting polar icepack that is an average of 3 m thick. However, as the Earth’s climate changes, the Polar Regions are warming and much of the icepack melts during the summer months. The Northwest Passage and the Northern Sea route have historically been important areas of trade and exploration. The Atlantic Ocean is the world’s second-largest Ocean with an area of 76,762,000 km2. It is located between Africa, Europe, and the Southern Ocean in the Western Hemisphere. It contains the majority of the Earth’s shallow Seas, but relatively few islands.  Geo-spatial Climate Formationinformation Classification of Earth’s and data and Regions Continentsprocessing of the World The shallow Seas found in the Atlantic Ocean basin are the: Baltic Sea, Black Sea, Caribbean Sea, Gulf of Mexico, North Sea, and the Mediterranean Sea. The average depth of the Atlantic Ocean is 3,926 m. Its deepest point is the Puerto Rico Trench which is some 8,605 m deep (Figure 1.11). Many streams and rivers discharge their water into the Atlantic Ocean. This basin also drains some of the world’s largest rivers including the Amazon, Mississippi, St. Lawrence, and Congo. It receives more freshwater from continental runoff than any other Ocean basin. The Atlantic Ocean is important to the world’s weather (as are all oceans) because strong Atlantic hurricanes often develop off the coast of Cape Verde, Africa, and move toward the Caribbean Sea from August to November. Figure 1.10 Continents and Oceans of the World The Indian Ocean is the world’s third-largest ocean and it has an area of 68,566,000 Km2. It is located in the area between Africa, the Southern Ocean, Asia, and Australia. The Indian Ocean has an average depth of 3,963 m. Its deepest point is at the Java Trench or Sunda Double Trench (Figure 1.11). The maximum depth reaches some 7,258 m. The waters of the Indian Ocean also include parts of the adjacent water bodies such as the Andaman, Arabian, Flores, Java, and the Red Sea as well as the Bay of Bengal, Great Australian Bight, Gulf of Aden, Gulf of Oman, Mozambique Channel and the Persian Gulf. The Indian Ocean is known for causing the monsoon weather patterns that dominate much of Southeast Asia and for having waters that have been historical checkpoints (narrow international waterways). Because of its proximity to the equator, this basin has the warmest surface Ocean temperatures. UNITUNIT TWO ONE Figure 1.11: Trenches (deepest parts of the Oceans) Source: www.trenchesandtrenches.weebly.com The Pacific Ocean is by far the world’s largest ocean basin with about 155,557,000 km2. It covers 28% of the Earth and is equal in size to nearly all of the land area on the Earth combined. It is located between the Southern Ocean, Asia, and Australia in the Western Hemisphere. It has an average depth of 4,028 meters, but its deepest point is the Challenger Deep within the Mariana Trench (Figure 1.11), about 10,924 m deep. This area is also the deepest point in the world. The Pacific Ocean has few marginal Seas but many islands. It is an important Ocean basin from the geographers’ perspective not only because of its size but also because it has been a major historical route of exploration and migration. The Southern Ocean is the world’s newest and fourth-largest Ocean. In the spring of 2000, the International Hydrographic Organization decided to delimit it as the fifth Ocean. In doing so, boundaries were taken from the Pacific, Atlantic, and Indian Oceans. The Southern Ocean extends from the coast of Antarctica to 60 degrees south latitude. It has a total area of 20,327,000 km2 and an average depth ranging from 4,000 to 5,000 m. The deepest point in the Southern Ocean is unnamed, but it is in the south end of the South Sandwich Trench (Figure 1.11) and has a depth of 7,235m.  Geo-spatial Climate Formationinformation Classification of Earth’s and data and Regions Continentsprocessing of the World Please answer the following question: 1. Locate the present-day Oceans and Continents on a sketch map and then show it to your teacher? 1.4. CHANGING POSITION OF CONTINENTS AND OCEANS OVER GEOLOGICAL TIMES This specific section acquaints you with the changing positions of Continents and the Ocean basins over the geologic times. At the end of this section, you will be able to: appreciate the changing positions of the Continents and Oceanic basins over the geologic time; and produce sketch maps showing the changing location of the Oceans and Conti- nents Keywords Continental drift Continents Oceans Plate tectonics Rodinia Brainstorming Activity 1.5 What do you know about the changing positions of Continents and Ocean basins? Please think individu- ally and then discuss with your classmates. UNITUNIT TWO ONE As can be observed from Figure 1.3 (on page 5), the location of the continents and oceans was not fixed. Due to plate movement (tectonics) the position of continents and oceans has been changing several times. For instance, during the Triassic period of the Mesozoic era ( 210 Ma), the earth’s continents were joined together forming one big continent called Pangaea (meaning the whole of the earth). Pangaea during this time was surrounded by on big water body named Panthalasu. During this time, Laurasia was located around the equator whereas Gondawana was located around the South-Pole. During the second stage, in the late Triassic period ( 180Ma), Pangaea started cracking because of continental drift. Following the rifting of Pangaea, Laurasia moved to the north. Africa, South America, India and Arabia started moving to the north too. Antarctica and Australia positioned around the South-Pole. Following the cracking of Pangaea, the oceans flooded the rifted area between the continents (see Figure 1.3). During the late cretaceous (65 Ma), the separation between Eurasia and North America increased. These two big continents positioned almost north of the tropic of cancer. Africa, South America, Arabia and India separated and positioned around the equator. Antarctica still placed at the South-Pole. Since the cracks between the separating continents widened, all the free areas were occupied by the Pacific, Atlantic, Arctic and southern oceans. After the separation of the Pangaea (see Figures 1.9 &1.12), North America and Eurasia are positioned in the northern hemisphere while India and Arabia joined Eurasia. Africa, South- America, and Australia are positioned around the equator; but Antarctica is still placed at the South-Pole. The Atlantic Ocean covered the area between Africa, Eurasia and the two America’s. The Pacific Ocean occupied the area between the America’s, Eurasia and Australia. The Arctic Ocean covers areas north of the Arctic Circle and areas between North America, Europe and Asia. The Indian Ocean covers the area between Africa, the Southern Ocean, Asia, and Australia. The Southern Ocean covered areas south of the Pacific, Atlantic and Indian Oceans and the coastal lands of Antarctica (see Figure 1.10).  Geo-spatial Climate Formationinformation Classification of Earth’s and data and Regions Continentsprocessing of the World Figure 1.12: Location of continents and Oceans during the late Cretaceous Today, seven continents and five Oceans makes-up the Earth. Most Continents occupy areas north of the equator while oceans dominate the southern hemisphere. The Pacific Ocean is located between Eurasia and the Americas while the Atlantic divides Africa and Eurasia from the Americas. The Indian Ocean also covered the area between Africa, Asia and Australia. The Arctic and Southern Oceans are centered at the North and South-Poles, respectively. Please answer the following question: 1. Describe how Continents and Oce- anic basins had been changing their positions over the geological times? 2. Please support your descriptions with sketch maps? UNITUNIT TWO ONE UNIT SUMMARY The geological timescale is the timeframe showing the estimated age of the Earth and its associated life-forms. It is established by Earth scientists through observation and analysis of rock layers. Two types of rock dating methods (Relative and Absolute dating) are used during rock dating activities. In relative dating, three principles (Original horizontality, Superposition, and Cross-cutting relationships) are in use. Radiometric isotopic dating methods are used for determining the absolute ages of rocks. The Earth is estimated to be 4.5 billion years old. The earliest life-forms assessed from fossilized bacteria are detected to be only about 3.5 billion years old. Scientists guess that early Earth was very hot and hostile to life. Its history is classified into Eons, Eras, Periods, and Epochs. Eons cover longer time units (billions of years) in the geological timescale. They are the Hadean, Archean, Proterozoic and Phanerozoic. The Phanerozoic Eon is the latest and divided into four Eras. Eras cover larger time units (hundreds of Ma). They include the Precambrian, Paleozoic, Mesozoic, and Cenozoic eras. The eras are further classified into periods that cover millions of years. They are 13 in number and each divided into relatively shorter periods named epochs. Of the eras, the longest and oldest is the Precambrian. It is the time when the earliest rocks solidified and were created. The Paleozoic is known to be the age of ancient life. The Mesozoic marks the age of middle life in the geological history of the Earth. The Cenozoic is the latest and is an era of developed mammals, birds, and modern humans. The formation of the Earth is attributed similar to the creation of other companion planets and the entire Solar System. The present-day continents are assumed to be developed by continental drift. At the beginning (during the Paleozoic and Mesozoic eras) all current continents were joined together forming a big landmass (Pangaea) embraced by a big water body named Panthalasu. In the mid of the Mesozoic, Pangaea started to break apart to form two major continents named Gondwanaland and Laurasia. These two supercontinents later split into several smaller landmasses. Due to continental drift, the Earth and its continents as well as the ocean basins have been continuously changing their shape, size, and position since the time of their creation. Their distribution has also been changing since time immemorial. For instance, the Supercontinent Pangaea was situated around the South Pole during the late Permian. Eurasia was also centered around the equator during that time. The present-day Oceans were not known by then. Today a large part of the continental landmass is located north of the equator. On the other hand, Oceanic environments are much more in the southern hemisphere. The proportion of land and water is not also equal over the planet Earth. Large areas (>71% of the Earth) are covered by water. Generally, the Earth’s continents and Oceans are not permanent and static. Their shapes, sizes, and locations are continuously changing with changes in time and earth processes.