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Earth Science. Part 1 Table of Contents 1.0 Introduction to Earth Science... 3 2.0 Earth Facts... 5 3.0 Earth s Coordinate System... 9 4.0 Quiz... 13 Measuring the Earth 2
1.0 Introduction to Earth Science Earth, the planet we live in, and everything around it, is wonderful and full of fascinating things. We study our planet, space, and the universe for the knowledge that allows us to understand things that happen and why they happen. With this, we, as humans, can make correct and informed decisions on everything we do in our home planet. This is how we define Earth Science. 1.1 Fields of Study Earth Science is divided into the following fields of study: Geology Geology is the study of the interior and the exterior parts of a planet. The field includes the structure, composition, physical properties, motion, and history of Earth. The word Geology comes from the Greek gế as earth and logos as speech. Meteorology The study of the Earth s atmosphere and weather processes is Meteorology. The word meteorology comes from the Greek word meteoros, which means high in the sky, and logia, the study of. Oceanography Also known as marine science, oceanography deals with the study of marine organisms, ocean ecosystems, ocean currents and fluid dynamics, as well as plate tectonics and sea floor geology. Astronomy Astronomy is the study of the evolution, motion or physics, and chemistry of all celestial objects. This includes the stars, the Sun, planetary systems, planets, galaxies, and everything outside the planet Earth. The word astronomy comes from the Greek word astron, meaning stars and nomos, the law or culture, which literally translates Astronomy as the law of the stars. 3 Measuring the Earth
1.2 Four Spheres or Classification Earth Science recognizes four spheres: Lithosphere The lithosphere is the solid part of the Earth. This includes the interior and the outermost rigid layer of the planet. Atmosphere The atmosphere is composed of layers of gases that cover the planet. The planet Earth has several atmospheric layers held by our planet s gravity. The atmosphere protects everything within the planet from harmful cosmic rays, radiation and other objects from outer space. Hydrosphere Hydrosphere pertains to the water at the surface of a planet, the properties and processes that involve it. Biosphere The biosphere is the ecosystem of a planet. It covers the life, flora and fauna in atmospheric, terrestrial and marine ecosystems. Figure 1.1 The Earth's atmosphere is the planet's protection from radiation and objects from space. It is also the reason why the sky and Earth, as seen from outer space, is blue. Gases in the atmosphere scatter blue light more than any other visible light wavelengths. Measuring the Earth 4
2.0 Earth Facts 2.1 Size, Shape and Composition The Earth is a terrestrial type of planet. It is the third planet from the sun. Here are some basic facts about our home: The shape of the Earth is an oblate spheroid, similar to a sphere that has bulging equator, or flattened poles. This unique shape is caused by the rotation of the Earth, which explains why the diameter at the equator is larger than the diameter from the poles. The polar diameter is approximately 12,714 km, while the equatorial diameter is 12,757 km. Figure 2.1. The shape of the Earth is not a perfect sphere, but an oblate spheroid. Why the Earth is NOT FLAT There are several evidences we see every day that proves the Earth is not flat. 1. The shadow of the Earth during lunar eclipses is semi-spherical. 2. When a ship is far at the sea, you can see that as it goes farther from you, the lower part of the ship is obscured first by the horizon. 5 Measuring the Earth
Figure 2.3. Evidence that Earth is not flat. The bottom part of a ship far at sea disappears first from the horizon. 3. The angle of the sun at noon varies over time and latitude. At the equator, the sun is overhead at noontime. But at the Tropic of Cancer or Capricorn, the sun isn t directly overhead, but at a certain angle from the horizon. 4. The height or altitude of the Polaris changes with latitude. 5. Pictures of Earth from the moon or outer space. 6. The planet s uneven gravitational field is an evidence of the true shape of the Earth. The Earth s gravitational field is stronger at the poles and weaker at the equator. Measuring the Earth 6
From FLAT to SPHERICAL Ancient cultures believed that the Earth was flat and that if you sail into the horizon of the ocean, you ll fall off from the edges. It was in 6 th century BC that Pythagoras theorized that all planets were spherical in shape. Around 140 B.C., Erastosthenes measured the circumference of the Earth by the Sun s summer solstice shadow. At Syrene, he knew that the sun is directly overhead during the summer solstice. But at Alexandria, where he was, he measured that the sun was at 83 or 7 from the zenith (overhead point). Using geometry of the two angles, he concluded that the distance from Syrene to Alexandria must be 7/360 of the circumference of the Earth. The age of the Earth is approximately 4.5 billion years old, based on the radiometric dating of the oldest meteorites found on Earth. The formation of the Earth should be close to the age of the Solar System. The oldest meteorite on Earth, therefore, should tell the most accurate age of the planet. The oldest meteorite discovered was the Canyon Diablo Meteorite at Barringer Canyon, Arizona, where the dating samples were shown to be between 4.53 and 4.58 billion years old. Figure 2.4 (Left) A fragment of Canyon Diablo Meteorite from Barringer Crater. Figure 2.5. (Right) The Barringer Crater at Arizona. 7 Measuring the Earth
NASA s Earth Fact Sheet Dimension Measurement Mass 5.97 x 10 24 kg Volume 108.32 x 10 10 km 2 Equatorial Radius 6378.1km Polar Radius 6356.8 km Ellipticity (flattening) 0.00335 Surface Gravity 9.798 m/s 2 Surface Acceleration 9.780 m/s 2 Ellipticity or oblateness pertains to the flattening of a spheroid s pole. The greater the value of ellipticity, the flatter the poles of an oblate spheroid. The most abundant minerals on Earth are silicates. The most abundant metal on the planet is aluminum; the second most abundant is iron. In the Earth s atmosphere, the most abundant gas is nitrogen (78%), and then oxygen (21%); other gases make up the remaining 1%. 2.2 Earth s Magnetic Field The Earth s magnetic field is similar to a magnetic dipole, which has south and north poles. The magnetic field is generated by the heat of the molten outer core, transferred towards conducting materials in the interior of the Earth. The heat generates electric current and the magnetic field of Earth. Figure 2.6 The Earth s magnetic North and South Pole representation. Charges, or the magnetic field, flow from the south to the north. Measuring the Earth 8
3.0 Earth s Coordinate System The Earth s geographic coordinate system is based on a spherical coordinate system. Though the Earth is not a perfect sphere, a coordinate system enables us to precisely pinpoint a location on Earth. The Earth s coordinate system is mainly composed of two linear systems: the latitude and the longitude. 3.1 Latitude Latitude lines are the imaginary parallel lines that run horizontally on a surface. The Earth s latitudes are concentric and coplanar circles that have different radii. The latitude also divides a sphere into its lower and higher hemispheres. These lines are named by angular measurements in degrees (1 = 60 minutes, 1 minute = 60 seconds). The latitude lines run from east to west, opposite of the rotational motion of the Earth. It s written in the format a b c, (degrees minutes seconds ). The latitude measurements start from the equator, for Northern hemisphere position, a b c North latitude, or to the Southern hemisphere a b c South. For example, a location in the Northern hemisphere is written as 15 27 18 North latitude. The highest latitude coordinates are at the poles at 90. Figure 3.1 Earth s major latitude lines 3.1.1 Major Latitudes Equator 9 Measuring the Earth
The Earth s equator is a major latitude line, denoted as the low latitude plane or 0 latitude. It is located at the plane perpendicular to Earth s axis of rotation. The length of the equator is approximately 40,075.16 km or 24,901.5 miles. Tropic of Cancer The Tropic of Cancer is located at 23 26 21" North latitude. It marks the position of the Sun at northern solstice, representing the extreme points of the Sun s path across seasons on Earth. It is also known as the Northern Tropic. Tropic of Capricorn The tropic of Capricorn is similar to the Tropic of Cancer, except that is it located at the southern hemisphere form the equator. It is located at 23 26 21" South latitude. During the December Solstice, the southern hemisphere of the Earth is tilted towards the Sun to the highest extent, letting the Sun appear in its highest altitude from the horizon Arctic Circle The Arctic Circle is currently located at 66 33 43" north of the Equator. Within this circle is the Arctic, the northern temperate zone where there are two major events: the midnight sun, when the sun shines the whole day, and the sunless night, when the Sun doesn t shine for 24hrs. When you are in this region, the sun is at its maximum or highest point during the June and December solstices. Antarctic Circle Located at the opposite side of the Arctic Circle, the Antarctic Circle is located at 66 33 43" south of the Equator. The Antarctic region likewise experiences the midnight sun and the sunless night during June and December solstices. 3.2 Longitude The longitude lines are imaginary vertical geographical lines. In a sphere, these lines have the same radii and all lines meet at the North and South Pole. These lines are also the basis of time zones all over the world. Every 15 is an hour difference. The time zones begin at the International Date Line (time zone 0) and moves to the right or eastward. Countries in the east are in earlier time zones than those in the west. For example, Singapore and Jakarta in Indonesia are one time zone apart. Singapore is found east of Jakarta. When it is 9:00am in Singapore, it is 8:00am in Jakarta. Measuring the Earth 10
Figure 3.2 Time differences in between Singapore, Jakarta and neighboring countries. 3.2.1 Major Longitude Lines Prime Meridian The Greenwich Prime Meridian is the 0 longitude, the reference line where all longitude lines begin. From the North Pole, it passes through an area in Yorkshire and the Royal Observatory at Greenwich, United Kingdom, then to the English Channel, France, Spain, and Gulf of Valencia. It then passes through Africa at Burkina Faso, Togo, Ghana, then to the Atlantic and Antarctica to the South Pole. Figure 3.3 The angle in between the longitude line is 15 degrees. There are 24 longitude lines. 11 Measuring the Earth
International Date Line The International Date Line is the 180 longitude line, opposite of the Prime Meridian. It is the line where date and time changes between the east and west territories. The International Date Line passes by the far east of Russia, islands in the Pacific and swings to the side of Fiji, Tonga and the Kermadec Islands of New Zealand. Measuring the Earth 12
4.0 Quiz Please fill in the blanks with the correct term or definition. 1. The horizontal lines in the Earth s coordinate system that divide the planet into the northern and southern hemispheres are called. 2. The circle is located at the northern hemisphere, while the circle is at the southern hemisphere. 3. The Earth s diameter pole-to-pole is (greater or less than) the diameter of the equator. 4. The is at the 0 longitude. 5. The is at the 180 longitude. 6. The shape of the Earth is. 7. At the equator, the sun at noontime is at the. 8. The time zone changes for every degrees of longitude. 9. Latitude lines run from to. 10. Longitude lines changes (positive angle) from to. 11. Time from the east is (earlier or later) than the west. 12. One evidence that the Earth is not a perfect sphere is that the gravitational field at the poles is (weaker or stronger) than the equator. 13. The event that occurs in the Arctic and Antarctica when the sun shines 24hrs a day is called. 14. New York is one time zone east of Chicago. If its 1:00pm at New York, it s at Chicago. 15. The most abundant mineral on Earth is ; metal ; gas. 13 Measuring the Earth