VIEWS: 23 PAGES: 68 POSTED ON: 7/11/2011
Introduction to Planet Earth Earth • Distance around the Earth is about 40,075 km at the equator. • Avg. distance from sun 149,600,000 km • Divided into two hemispheres-Northern and Southern. • Three main features are the – Land – Lithosphere – Water – Hydrosphere – Air -- Atmosphere The Atmosphere • Theorized - 4 billion years ago atmosphere contained two deadly gases, methane and ammonia. • Through chemical reactions triggered by sunlight over many years the deadly gases and water vapor caused nitrogen, hydrogen, and carbon dioxide to form. • A layer of Ozone gas formed from oxygen – Prior to this layer forming, only microscopic organisms lived below the surface of the oceans. After the Ozone Layer • Blue green bacteria surfaced from the water and used the energy from the sunlight to combine carbon dioxide and water to produce food which is a byproduct of Oxygen. Oxygen remained near surface. • More green plants began to grow, again increasing the Oxygen content. • Teachers' Domain: Life Before Oxygen Present Atmosphere • A mixture of gases – Nitrogen 78% (most abundant) – Oxygen 21% – Carbon Dioxide – Water Vapor – Argon Less than 1% – Other trace gases First: Nitrogen Nitrogen cycle 6. Movement of nitrogen in air back to ground 5. 3. Animal eats plants 4. 1. Nitrogen fixing 2. Plants use Bacteria convert to nitrates nitrates 1. Oxygen: used directly from atmosphere by most plants and animals. 2. Carbon Dioxide Cycle: removed from atmosphere by plants and returned by respiration of plants and animals. The decay of plants and animals returns carbon dioxide to the air. But the burning of fossil fuels (oil,coal) adds carbon dioxide to air---concern of dangerous levels. -----Traps more of the sun’s heat in atmosphere which increases the temperature of Earth…. Greenhouse effect. Water Vapor— Causes weather conditions— clouds, fog, dew, rain, snow fall Absorbs heat energy given by sun. Solid Particles—dust, smoke, dirt. The Water Cycle Teachers' Domain: Global Water Distribution The WATER CYCLE refers to the continuous movement of water between the Earth’s surface and atmosphere. Sedimentary-Earth’s Natural Water Filter • Surface water often contains contaminants. • Spring water is filtered through sediment, sand, and gravel where solids are suspended in water and trapped in the sediments. In the end, water that bubbles out or pumped from aquifers several hundred feet below the surface is on average more than 99.9 % free of contaminants. Exosphere Above a height of about 500km is the exosphere, a layer where the atmosphere merges into space. Satellites are stationed in this area, 500km to 1000km from Earth. Thermosphere The thermosphere is the fourth layer in the atmosphere, between 80km and 110km above the Earth. Space shuttles fly in this area and it is also where the aurora lights are found. Auroras are wispy curtains of light caused when the sun strikes gases in the atmosphere above the Poles. The temperature is high in this layer. Mesosphere Beyond the stratosphere the air is very thin and cold. This area is known as the mesosphere, and is found between 50km and 80km above the Earth’s surface. The upper area of this region is the coldest part of the atmosphere. This layer helps protect Earth from meteroids. Stratosphere The stratosphere is the second layer of air above the Earth’s surface and extends to a height of 50km. It is here that we find the ozone layer. The ozone layer absorbs much of the sun’s harmful radiation that would otherwise be dangerous to plant and animal life. The jet stream winds blow in this area. Troposphere The troposphere is the layer closest to the Earth, approximately 11km high. Weather occurs only in the troposphere because it is this layer that contains most of the water vapor. Layers of the Atmosphere OZONE 1. Solar Radiation 100% 30% lost to space by reflection & scattering 5%backscattered to space by atmosphere 20% reflected from clouds 20% of radiation absorbed by atmosphere & clouds 50% of direct & diffused radiation 5% reflected from Absorbed by land & sea land-sea surface 30% lost to space by reflection & scattering 50% of direct and diffused Radiation absorbed by Land and sea. Figure 10a: Sunlight warms the earth's surface only during the day, whereas the surface constantly emits infrared radiation upward. Without water vapor, CO2, and other greenhouse gases, the earth's surface would constantly emit infrared radiation (IR); incoming energy from the sun would be equal to outgoing IR energy from the earth's surface. Without the greenhouse effect, the earth's average surface temperature would be -18°C (0°F) . Earth’s avg. temp is 15 deg C with the Greenhouse effect. Nitrogen Greenhouse Gases: Oxygen Water Vapor, Carbon Dioxide, Methane, Nitrous Argon Oxide, Ozone Greenhouse effect is not a bad thing! It keeps the earth warm enough for us to live here. Without the greenhouse effect, the earth would be a cold planet and would not be able to support life. Gases like carbon dioxide and methane let the sun's radiation into our atmosphere, but don't let the heat that is radiated back from the earth's surface out of the atmosphere into space. This is similar to how an actual greenhouse keeps the plants inside warm, giving the effect its name. The Greenhouse Effect Teachers' Domain: Global Warming: The Physics of the Greenhouse Effect So far the Earth seems to be the only planet to support life • It is the only planet with liquid water and its perfect distance from the sun. Its atmosphere has the right mixture of gases and protection layer from meteor impacts and dangerous rays. Life forms have adapted to land, water, and air. • Teachers' Domain: Ingredients for Life: Water • Discussion groups : ―What significance or functions does each layer of the Earth’s atmosphere have on living organisms?‖ 1300 km Earth’s Interior 2900 km 2250 km 1300 km Mantle made mostly of the elements silicon, oxygen, iron, and magnesium. Composition of mantle found by studying rocks of volcanoes and ocean floor. Earth’s Interior • Major layers – Crust – thinnest, solid • Moho – Boundary between Crust & Mantle – Mantle – most massive – Inner Core – liquid (Ni & Fe) – Outer Core – solid high pressure (Ni & Fe) • Sub layers – Lithosphere- crust + upper mantle – Asthenosphere – soft flowing mantle When a solid has the ability to flow it has the property of plasticity. • The rock in the mantle can flow like a thick liquid. The high temperature and pressure in the mantle allow the solid rock to flow slowly, thus changing shape. How did scientists learn about the Earth’s interior? • By studying seismic waves produced by earthquakes. • Seismic Waves Earth’s Crust: Continental and Oceanic • The outermost layer – Very thin compared to other layers – Most cannot be seen due to soil, rock, and water – Made up of 3 types of solid rocks • Igneous rocks • Sedimentary rocks • Metamorphic rocks Igneous Rocks • Form when hot liquid rock from deep within the Earth cools and hardens as it reaches the surface Large crystals Igneous rock from Maine Sedimentary Rocks • Form when sediments – small pieces of rocks, sand, and other materials are pressed and cemented together by the weight of others over long periods of time. Sedimentary rock from Utah Metamorphic Rock • Sometimes sedimentary and igneous rocks are subjected to pressures so intense or heat so high that they are completely changed. Metamorphic rock from Maine Thickness of the crust varies • Oceanic crust ~ 3 mi thick – silicon, oxygen, iron, and magnesium (constantly recycled). • Continental crust is about 25 mi thic – made mostly of silicon, oxygen, aluminum, calcium, sodium, and potassium. More silica rich than oceanic crust. Earth’s Lithosphere is made up of the crust and upper part of the Mantle Continental Drift • Alfred Wegener – Continental Drift • Puzzle pieces South America & Africa • Geology (rock) • Paleontology (fossils) Plate Tectonics • What is a ―Tectonic (Lithospheric) Plate‖ ? – massive, irregularly shaped slab of solid rock – composed of both continental and oceanic lithosphere. • Lithospheric plates sliding along Asthenosphere – Plate Boundaries (4.1) – Formation of Ocean Floor (4.2) – Rifting (4.6) The Earth’s Changing Surface • Forces within the Earth itself push and pull on the rocks of the Earth’s crust changing its shape and volume. They also move up, down, and sideways causing them to break, tilt, and fold. This is called deformation. Three Types of Stress 1. Compression 2. Tension 3. Shearing Types of Stress Fracture joints Stress sometimes causes rocks to break or crack • 1. Fault—Movements along a fault can be up, down, or sideways. – Earthquakes often form along faults in the Earth’s crust. Fault Foot Hanging Wall Wall Foot Wall Hanging Wall Compression Lateral Fault Foot Wall Hanging Wall http://www.earthguide.ucsd.edu/earthguide/diagrams/faults/index.html Normal Fault L side lower, hanging wall • Big Bend, Boquillas Canyon between Texas Footwall and Mexico. Thrust (Reverse) Fault Example Hanging wall sliding over foot wall Example Lateral Fault (Las Vegas, Nevada) Fault-block mountains are formed by the raising of huge blocks of the earth's surface relative to the neighboring blocks. Mountains sometimes form when many layers of the Earth's crust are moved vertically upward at fault lines by pressures caused by plates colliding. Fault Block Mountain Form along a fault line -- the rocks on one side of the fault are forced upward, while the rocks along the other side sink. Fault Block Mountains Juniper Canyon Rift Valley When a block of rock between two normal faults slide down. Rift Valley in Kenya 2. Folding • Sometimes when stress is applied to rocks of the crust, the rocks bend but do not break. * Can fold either upward—anticline or downward—syncline * Some large enough to form mountains Folded Mountains are believed to have been formed when the edges of two adjacent rock layers were pushed together causing the layers to buckle like a wrinkled rug. Scientists have learned that under great pressure and steady force, rocks can actually bend rather than break. Anticline and Syncline Syncline Anticline Factors that determine whether rocks will FAULT or FOLD 1. Temperature 2. Pressure 3. Rock type – Brittle (sandstone) likely to break – Ductile (rock salt) likely to fold 4. Stress – Gradual—will usually fold – Sudden—will usually break Plateaus • A large area of flat land that is raised high above sea level. • Consist of horizontal rock layers. • Layers remain flat. • May be formed by a slow flat topped fold, vertical faulting (crust pushing upward), or by a series of molten rock flows. Molten Rock • Flowing on the surface of Earth: Lava • Deep within the Earth: Magma • Lava piles up and forms a plateau Domes • Sometimes magma pushes upwards but does not reach the Earth’s surface causing the rock layers above to fold upward. • The uplifted area caused by rising magma forms a dome. • Domed Mountains appear to be formed when molten rock is forced upward beneath an overlying rock layer, pushing the rock above into a blister-like dome - molten rock does not reach the surface. Domed mountains are often found in the same areas as volcanic mountains since they also result from volcanic activity. As you recall beneath the As you recall…. Earth’s crust is the mantle, made of rock that flows slowly. The rocky crust floats on top of the mantle, exerting a downward force. The mantle also exerts an upward force on the crust. A balance exists between the two forces called ISOSTASY. •Isostasy If the Mississippi River dumps tons of mud and sand particles into the Gulf of Mexico, will the Gulf become shallow and eventually disappear?