The study of the earth is called geology, and scientists who study the earth are geologists. The earth ranks fifth in size among the planets. It has a diameter of about 13, ooo kilometers. The earth travels 958 million kilometers around the sun in 365 days, 6 hours, 9 minutes, and 9.54 seconds. This length of time is called a sidereal year. The art’s axis does not stick straight up from the orbital plane. It tilts about 231/2o from the straight-up position. This tilt and the earth’s motion around the sun cause the change of seasons. The earth’s surface is about 70 per cent water-almost all of in the oceans. Land makes up about 30 per cent. The oceans have an average depth of 3,730 meters. The deepest know part of any ocean is the Mariana Trench, a long, narrow depression under the Pacific Ocean south-west of Guam. Its bottom lies 11,033 meters be low the surface. The earth’s land is an average height of 840metres above sea level. The highest land is the top of Mount Everest in Asia, 8,848metres above seal level. The lowest land is the Dead Sea shore in Asia, about 399 meters below sea level. The earth is probably at lest 41/2 billion years old. The oldest ever discovered are about 4:3 billion years old.Temperatures at the earth’s surface range from the highest ever recorded 58 0C at Al Aziziyah, Libya, to the lowest, 89. 6 0C, which was recorded at Vostok Station in Antarctica. The northernmost point of the world is the geographic North Pole, in the Arctic Ocean. The northernmost point on land is Kaffekubben Island, north of Greenland. The southernmost point of the world and the southernmost point on land is the geographic South Pole, which is on the continent of Antarctica. The westernmost point on land according to the path of the International Date Line would be Attu Island. Alaska. The easternmost point on land according to the path of the International Date Line would be Caroline Island Kiribati.

      TROPOSPHERE: It is the lowest layer of Atmosphere. Most of the weather phenomena take place in this layer. Within the Troposphere, the temperature of the air generally decreases as the altitude increases.

      STRATOSPHERE: The thickness of the Stratosphere is about 40-45 kms. Aero plane usually flies in this layer. The ozone in this layer absorbs harmful ultraviolet radiation from the Sun.

      MESOSPHERE: It lies between the stratosphere and the thermosphere, the uppermost layer of the atmosphere. The lowest temperatures in the earth’s atmosphere occur at the top of Mesospher.called the Menopause.
      THERMOSPHERE: Its lower part is called the ionosphere, contains electrically charged particles called inns. These particles reflect radio waves back to the earth’s surface and enable wireless communication. The upper portion of this layer is called the Exosphere.

      Equator is the great circle of the earth that lies halfway between the North and South poles. The imaginary line divides the earth into two equal parts called the Northern Hemisphere and the Southern Hemisphere. The circumference of the earth at the equator is about 40, 76 kilometers. Each degree of longitude at the equator equals 111.32 kilometers.
      Greenwich Meridian is a north-south line that passes through Greenwich, a borough of London, on a map of the earth. The Greenwich Meridian is often called the Prime Meridian. Is has been designated 0o longitude, and all other meridians of longitude are numbered east or west of it The Greenwich  Meridian is also the starting point for the world’s time zones. There are 24 time zones, each with a width of 15o longitude.

      The International Date Line follows the 180th meridian for most of its distance. The 180thmeridian is exactly halfway around the world from Greenwich, a borough of London. Another imaginary line, called the prime meridian or Greenwich meridian, marks 0o of longitude at Greenwich.

      Worldwide time zones were established in 1884.

      An international conference in 1884 set up 12 time zones west of Greenwich and 12 to the east. These zones divide the world into 23 full zones and two half zones. The 12th Zone east and the 12 th zone west are each half a zone wide. They lie next to each other and are separated by an imaginary line called the International Date Line. 

      Tropic of Cancer is an imaginary line that traces the northern boundary of the earth’s Tropical Zone It marks the farthest limit north of the equator where the sun can appear directly overhead. The line lies 23o 27 north of the equator. The vertical rays of the sun shine down on the Tropic of Cancer at noon on the day of the summer solstice which is June 20or 21.
      The Tropic of Capricorn crosses northern Chile and Argentina, Paraguay, and southern Brazil in Botswana, South Africa Mozambique, and Madagascar. The Tropic of Capricorn also passes through the middle of Australia.
        0o Prime Meridian or Greenwich Meridan.
       180o International Date Line (passes through the Pacific Ocean).


      • Rotation is the turning of the earth on its axis from west to east. It takes twenty four hours to complete one rotation. The rotation of the earth causes day and night.
      • The movement of earth around the sun is called revolution. The earth takes 365 ¼ days to make one complete revolution around the Sun. For the sake of convenience, we take 365 days as a year and ignore 5 hours, 48 minutes, 46 seconds, Thus in 4 years, we ignore about 4x6=24 hours or a full day. In order to compensate these 24 hours, we take 366 days fourth year. Such a year of 366 days is called leap year.
      • Equinox is either of the two days of the year when the sun is directly above the earth’s equator At these times, the days and nights are of nearly equal length everywhere on the earth.
      • The equinoxes occur on March 20 or 21 and September 220r23. In the Northern Hemisphere, the March equinox marks the beginning of spring and is often called the vernal equinox .The word vernal means of spring The September equinox marks the beginning of autumn and is called the autumnal equinox. The seasons are reversed in the Southern Hemisphere.

      The cycle of seasons
      Date ----------Southern------------Southern  ------------Northern--------------Northern
                                       Hemisphere           Hemisphere             Hemisphere              Hemisphere    
                                       Season                   day & night              Season                      day & night

       21 March-----autumn(fall)----------equal-------------------spring---------------equal
       21 June--------Winter----------------shortest day------------summer------------longest day
      23  Sept------Spring------------------equal-------------------autumn(fall)--------equal
       22  Dec------summer-----------------longest day----------winter ----------------shortest day

      The summer solstice occurs when the sun reaches its most northerly point, directly overhead at the Tropic of Cancer (23o 27 north latitude).  At the winter solstice , the sun appears at its most southerly position, directly overhead at the Tropic of Capricorn (23o 27 south Latitude)

      The summer solstice occurs on approximately June 21 and the winter solstice on about December 21. In the Northern Hemisphere, the day of the summer solstice is the longest day of the year and marks the beginning of summer. Similarly, the winter solstice occurs on the shortest day of the year and indicates the beginning of winter. In the Southern Hemisphere, summer and winter are reversed.

      Aphelion is the position of the Earth in its orbit when it is at its greater distance from the Sun.

      Perihelion is the position of the Earth in its orbit when it is at its nearest distance from the Sun.

      Apogee is the position of the Moon or any other heavenly body when it is at its greatest distance from the Earth.
      Perigee is the position of the Moon or any other heavenly body when it at its shortest distance from the Earth.

      Do you know?

      Summer Solstice---------------June 21
      Winter Solstice-----------------December 22
      Vernal Equinox-----------------March 21
      Autumn Equinox---------------September 23
      Perihelion-----------------------January 3
      Aphelion------------------------July 4

      • Volcano is an opening in the earth’s surface through which lava, hot gases and rock fragments erupt.
      • The word “volcano” derives from Vulcan.
      • The processes that create volcanoes and other volcanic structures are called volcanism or volcanism.
      • Most volcanoes are found along a belt, called the Ring of Fire that encircles the Pacific Ocean volcano logy.
      •  Active volcanoes erupt constantly. The eruption is generally quiet but occasionally becomes violent. A famous active volcano active volcano is Stromboli, which lies on an island off the coast of Italy.
      • Intermittent volcanoes erupt at fairly regular periods. Such volcanoes include Mount Asama in Japan, Mount Etna in Sicily, and Hawaii’s Hualalai.
      • Dormant volcanoes have become inactive, but not long enough to know whether they will erupt again. Such “sleeping” volcanoes include Lassen Peak in California, U. A. S. and Paricutin in Mexico.
      • Extinct volcanoes have been inactive since the beginning of recorded history. Aconcagua in Argentina and Mount Kenya in Kenya are extinct volcanoes. They probably will not erupt again.


      • Volcano---------------------------LOCATION
      • Cotopaxi--------------------------Ecuador
      • Krakatau--------------------------Indonesia
      • Mauna Loa-----------------------Hawaii, U.S.A.
      • Mount Etna----------------------Sicily, Italy
      • Stromboli------------------------Mediterranean
      • Vesuvius-------------------------Italytaly

      • The Sahara, the world’s largest desert, stretches across northern Africa from the Atlantic Ocean to the Red Sea. It covers about 9 million square kilometers.
      • Other large deserts include the Australian Desert the Gobi Desert in China and Mongolia and the Kalahari Desert in southern Africa.
      • Desert animals include many kinds of insect’s spiders, reptiles, birds, and mammals. Deer, foxes, wolves and other animals may visit a desert after a rainfall.
      • Most deserts lie between the latitudes of 15o and 35o on each side of the equator.
      •  Gibson Desert forms part of the plateau of Western Australia.
      • Thar Desert stretches northwest of the Aravalli Range in India across Rajasthan to the Indus River plain in Pakistan. It is also called India Desert.


       Sahara---------------------------North Africa
       Libyan---------------------------North Africa
      Great Victoria------------------Australia
      Gobi----------------------------Mangolia / China
      Patagonia---------------------Argentina & Chile

      • Ocean is the great body of water that covers more than 70 per cent of the earth ‘s surface
      • Oceanography is the scientific study of the physical, chemical, and biological processes that maintain its structure and motion.
      • In the southern hemisphere there is a circumpolar zone (the Southern ocean) that connects the southern extremities of the S-shaped Atlantic, the vast triangular Pacific and the smaller India Ocean.
      • Pacific Ocean, largest and deepest of the world’s five oceans, covering more than a third of the Earth’s surface and containing more than half of its free water. The largest landmass entirely within the Pacific Ocean is the island of New Guinea- the second largest island in the world.
      • The name Pacific, which means peaceful, was given to it by the Portuguese navigator Ferdinand Magellan in 1520.
      • The Atlantic Ocean is the second-largest ocean covering approximately one-faith of the Earth’s surface. The ocean’s name, derived from Greek mythology, means the “Sea of Atlas.” The oldest known mention of this name is contained in the histories of Herodotus around 450 BC. The Atlantic Ocean is an S-shaped north-south channel.
      • The Indian Ocean is the third largest body of water in the world, covering about 20% of the Earth’s water surface.
      • The Arctic Ocean, located mostly in the Arctic North Polar Region, is the smallest of the world’s five oceans.
      • The Southern Ocean, also known as the South Polar Ocean (and formerly the Antarctic Ocean), is the body of water encircling the continent of Antarctica. It is the world’s fourth largest ocean and the latest to be defined.


      Deepest Point in the World (and Pacific Ocean)
                   Challenger Deep, Mariana Trench, Waterier Pacific Ocean. 35, 840 feet   
      Deepest Point in the Atlantic Ocean
               Puerto Rico Trench: 28, 374 feet
      Deepest Point in the Arctic Ocean
                     Eurasia Basin 17, 881 feet
      Deepest Point the Indian Ocean
                   Diamantine Trench 8, 047 meters

              NAME                                           LINKS
      1. Gibraltar-------------------------------Mediterranean and Atlantic Ocean
      2. Bering---------------------------------Arctic Ocean and Bering Sea
      3. Dover----------------------------------English Channel and North Sea
      4. Florida---------------------------------Gulf of Mexico and Atlantic Ocean
      5. Malacca------------------------------ -South China Sea and Indian Ocean
      6. Magellan------------------------------South Pacific and South Atlantic
      7. Palk------------------------------------Bay of Bengal and Indian Ocean
      8. Bab el Mandeb-----------------------Red Sea & Arabian Sea
      9. Hormuz-------------------------------Bahrain and Qatar


      • Greenland is the largest island in the world, It also known as Kalaallit Nunaat island. Greenland is a self-governing part of Denmark, situated between the North Atlantic and Arctic oceans.
      • New Guinea Island is situated in the western Pacific Ocean, north of Australia. It is the second-largest island in the world, after Greenland.
      • Borneo is the third largest island in the world. It has an area of 743,330 km2 and is located at the centre of the Malay Archipelago and Indonesia. Borneo is considered to be part of the geographic region of Southeast Asia. In Indonesia, the island is always referred to as Kalimantan.
      • Sumatra is the sixth largest island of the world and is the largest island entirely in Indonesia (two larger islands, Borneo and New Guinea, are partially in Indonesia). An ancient name for Sumatra was Swarna Dwipa.
      • The Andaman Islands are a group of island in the Bay of Bengal, and are part of the Andaman and Nicobar Islands Union Territory of India. There are 576 islands in the group, 26 of which are inhabited. Barren Island is located in the Andaman Sea, one of the most easterly of the Andaman Island. It is the only confirmed active volcano in South Asia. The first recorded eruptions of the volcano dates back to 1787. Since then the volcano has erupted more than 6 times, most recently on May 2, 2006.
      • Indonesia is the largest archipelago in the world.


      • Nile River is the longest river in the world. It flows for 6, 671 kilometers through northeast Africa. The Nile rises near the equator and flows into the Mediterranean Sea. The Nile has two major tributaries, the White Nile and Blue Nile
      • Amazon River is the world’s second longest river and the chief river of South America. It is sometimes known as ‘The River Sea’ The Amazon is 6,437 kilometers long.
      • Congo River is the fifth longest river in the world. The River Congo is the second longest river in Africa. The river also has the second-largest flow in the world and the second-largest drainage basin of any river, behind the Amazon.
      • The Limpopo River rises in the interior of Africa, and flows generally eastwards towards the Indian Ocean. It is also called the Crocodile River. Vasco da Gama was the first European to sight the river, when one of his expeditions anchored off the mouth in 1498.
      • The Yangtze River is the longest river in Asia and the third longest in the world after the Nile in Africa and the Amazon in South America. The river is about 6, 211 km long and flows from its source in Qinghai Province in western China, into the East Chin Sea.
      • Volga River is the longest river of Europe with a length of 3, 690 km, and forms the core of the largest river system in Europe.


        Colombo-------------------------------Kaliganga-------------------------Sri Lanka
        Cologne --------------------------------Rhine------------------------------Germany
        George Town---------------------------Berbice----------------------------Guyana
        New York-----------------------------Hudson-----------------------------U. S. A
        New Orleans--------------------------Mississippi------------------------U. S.A
        Prague---------------------------------Vitava----------------------------Czech Republic