G10 1st Quarter Exam Reviewer Earth Science, Study notes of Earth science

Download G10 1st Quarter Exam Reviewer Earth Science and more Study notes Earth science in PDF only on Docsity! What tells us that the inner core is made up of iron? • Iron and nickel are both dense and magnetic. • The overall density of the earth is much higher than the density of the rocks in the crust. • Meteorite analysis have revealed that the most common type is chondrite. Chondr/te-contains iron, silicon, magnesium and oxygen; some contains nickel. The whole earth and the meteorite roughly have the same density, thus the Earth's mantle rock and a meteorite minus its iron, have the same density. The Earth's Mechanism •!• The Continental Drift -In 1912, Alfred Wegener, a German meteorologist, proposed a theory that about 200 million years ago, the continents were once one large landmass. He called this landmass Pangaea. Landmass Pangaea-Greek word which means "All Earth ." -Pangaea started to break into two smaller supercontinent called Laurasia and Gondwanaland during the Jurassic Period . These smaller supercontinents broke into the continents and these continents separated and drifted apart since then. Evidence: l. The Continental Jigsaw Puzzle -the most visible and fascinating evidence that these continents were once one is their shape. -the edge of one continent surprisingly matches the edge of another. 2. Fossils -preserved remains or traces of organisms (plants and animals) from the remote past. - Fossilized leaves of an extinct plant Glossopteris were found in 250 million years old rocks. -fossils were located in the continents of Southern Africa, Australia, India, and Antarctica, which are now separated from each other by wide oceans. -Mesosaurus and Lystosaurus­ freshwater reptiles. Fossils of these animals were discovered in different continents, such as in South America and Africa. It is impossible for these reptiles to swim over the vast oceans and move from one continent to another. Fossil5. 'Ne: c iillso fcJr.t! in Antarctica . 3. Rocks - The rocks themselves also provide evidence that continents drifted apart from each other. -Rock formations in Africa line up with that in South America as if it was a long mountain range. In 1909, Yugoslavian seismologist Andriia Mohorovicic (moh-haw­ rohvuh-chich)-fou nd out that the velocity of seismic waves changes and increases at a distance of about 50 kilometers below the Earth's surface. Mohorovicic discontinuity -in honor of Mohorovicic, and is short termed Moho, is a boundary between the Earth's crust and the mantle. Shadow zone-an area of the Earth's surface were seismographs cannot detect direct P waves and/or S waves from an Earthquake. This is due to liquid layers/structures within the Earth's surface. According to German seismologist Beno Gutenberg -The existence of a shadow zone could only be explained if the Earth contained a core composed of a material different from that of the mantle causing the bending of the P-waves Gutenberg discontinuity -mantle-core boundary -refers to the transit ion zone between the mantle and the core. [In 1936, the innermost layer of the Earth was predicted by Inge Lehmann. a Danish seismologist.]- He discovered a new region of seismic reflection within the core. Thickness of the different layers of the Earth. Crust-40km Mantle-2900 km Outer core-2200 km Inner core-1278 km The Composition of the Earth's Interior . .. , •.. . ,. f . .. ~ _ j ' The Earth is composed of three major layers: the crust, mantle, and core which is subdivided into outer and inner core. ► The Crust -thinnest and the outermost layer of the Earth that extends from the surface to about 32 kilometers below. -Underneath s01,,e r11ountains, the crust's thickness extends to 72 kilometers. -The Earth's crust is subdivided into two regions: 1. Continental Crust -mainly made up of si licon, oxygen, aluminum, calcium, sod ium, and potassium. Convection Current -As a substance like water is heated, the less dense particles rise while denser particles sink. Once the hot less dense particles cool down, they sink, and the other l,ess dense particles rise. his is exactly what happens in the Earth's mantle. -rotate very slowly, as they move and drag the plates along. Ridge push-this process occurs as the older seafloor sinks, the weight of the uplifted ridge pushes the oceanic crust toward the trench at the subduction zone. Slab pull-other possible process involved in the tectonic plate movement. The weight of the subducting plate pul ls the trailing slab into the subduction zone just like a tablecloth slipping off the table and pulling items with it. Glossary of Te~ • Asthenosphere-soft, weak upper portion of the mantle where the lithospheric plates float and move around ..., Continental Drift Theory­ states that all the continents were once one large landmass that broke apart, and where the pieces moved slowly to their current locations 4 Convection current-current in the mantle because of the heat from the inner layers of the Earth, and is the force that ~ ~ .. ~ ~ .. ~ ~ drives the plates to move around Lithosphere-the topmost, solid part of the Earth that is composed of several plates Lithospheric Plates-the moving, irregularly-shaped slabs that fit together to form the surface of the Earth Mid-ocean ridge-area in the middle of the ocean where a new ocean floor is formed when lava erupts through the cracks in the Earth's crust Mohorovicic Discontinuity (MohoJ-the boundary that separates the crust and the mantle Plasticity-the ability of solid to flow Seafloor spreading- the process by which new ocean floor is formed near the mid- ocean ridge and moves outward Subduction-the process in which the crust plunges back into the Earth Tectonlcs-b~ c)r,~.~ of g~c.lo:;V that deals with the movements that shape the Earth's crust 4. Coal Deposits -Coal beds were formed from the compaction and decomposition of swamp plants that lived million years ago. -These were discovered in South America, Africa, Indian subcontinent, Southeast Asia, and even in Antarctica. 5. The Seaf/oor Spreading -According to this theory, hot, less dense material from below the earth's crust rises towards the surface at the mid-ocean ridge. This material flows sideways carrying the seafloor away from the ridge, and creates a crack in the crust. The magma flows out of the crack, cools down and becomes the new seafloor. -The process of seafloor spreading allowed the creation of new bodies of water. -Seafloor spreading is also pulling the continents of Australia, South America, and Antarctica away from each other in the East Pacific Rise. East Pacific Rise-one of the most active sites of seafloor spread ing, with more than 14 centimeters every year. Findings that sup~rt Seaflool'i Spreading Theory: 1. Rocks are younger at the mid­ ocean ridge. 2. Rocks far from the mid-ocean ridge are older. 3. Sediments are thinner at the ridge. 4. Rocks at the ocean floor are younger than those at the continents. •!• Magnetic Reversal-called magnetic 'flip' of the Earth. It happens when the North Pole is transformed into a South Pole and the South Pole becomes the North Pole. This is due to the change in the direction of flow in the outer core. Plate Tectonic Theory -provided an explanation about the movement of the lithospheric plates. - his theory evolved from the two former theories and was developed during the first decades of the 20th century. There are three types of plate movements 1 Divergent-separation of two plates. 2. Convergent-cnll1~ion of two plates. 3. Transform-sliding past each other. What facllltates the movement of the plates? Heat is produced in the core that produces convection in the mantle. This convection causes the plate to move around. .Kte,/Qht -The thickness of the continental solid, since both S-waves and P- crust is mostly 35-40 kilometers . waves pass through it. -found under land masses, is made -mostly made of the elements of less dense rocks such as silicon, oxygen, iron and granite. 2. Oceanic crust -around 7-10 kilometers thick which its average thickness is 8 kilometers. -It is found under the ocean floor and is made of dense rocks such as basalt. -heavier than the continental crust. [Crust consists of two layers. The upper layer is composed of granite and is only found in the continental crust. Elements In the Earth's aust Oxygen-46.60% Slllcon-27. 72% Aluminum-8.13% lron-5.00% Calclum-3.63% Sodium-2.83% Potassium-2.59% Magnesium-2.09% Titanium-0.40% Hydrogen-0.14% ► Mantle -Beneath the crust, which extends to about 2900 kilometers from the Earth's surface. -makes most of the Earth's volume-(about 80% Total Volume) and mass (about 68% Total Mass). -made up of silicate rocks, and contrary to common belief, is magnesium. Crust and the uppermost part of the mantle form a relatively cool, outermost rigid shell called Lithosphere. Lithospheric p/ates-lithospehere subdivided into portions. -move relative to each other. Asthenosphere -Beneath the lithosphere lies the soft, weak layer. -made of hot molten material. -temperature is about 300 - B00*C ► Core -subdivided into two layers: ► OuterCore - 2900 kilometers below the Earth's surface -2250 kilometers thick and is made up of iron and nickel. -temperature in the outer core reaches up to 2000*C at this very high temperatur2 . i.''.-'.1 ar:d ;1:dc1!! melt. ► lnnerCore -made up of solid iron and nickel - has a radius of 1300 kilometers. -temperature reaches as high as S000*c. -extreme temperature could have molten the iron and nickel but it is believed to have solidified as a result of pressure freezing