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Transcript
The Dynamic Earth Chapter 3 The Earth as a system: -The Earth is a system that is made of rocks, air, water and living things that all interact with each other. Geosphere: All of the rock, soils and sediments on the Earths surface. Atmosphere: The mixture of gases that make up the air we breathe 78% nitrogen, 21% oxygen, 1% trace gases The hydrosphere: All of the water on the Earths surface. The Biosphere: Is the part of the Earth where life exists. This ranges from the bottom of the oceans to about 9 Km above the Earth’s surface. Section 1: The geosphere Discovering the Earth’s interior: Scientists have used data from seismic waves produced by Earth quakes in order to learn about the inside of the earth. Primary, or P waves go twice as fast as S waves and can travel through solids and liquids (like the liquid outer core). Secondary or S waves arrive after the P waves and are blocked by liquids (and can not travel through the liquid outer core). To find the epicenter, you need three stations that recorded the Waves. Then you need to find the difference in P and S wave arrival times. Then use a chart to find the epicenter distance. Then draw a circle on a map for each station. Where the three circles meet is the location of the epicenter. This is called Triangulation. Composition of the Earth • Scientists have divided up the Earth in to three basic layers based on their chemical composition. • The Crust, Mantle and Core. • Crust: Earths thin rocky outer layer made mostly of lighter elements. • Mantle: The rock layer of medium density that is below the crust. • Core: Inner most layer composed of the densest elements. Structure of the Earth • The earth can be divided into 5 layers based on physical properties. • Lithosphere (Lithos is Greek for stone): Earth’s outer layer of rock and is divided into large slabs called tectonic plates. • Asthenosphere (Asthenos is Greek for weak): is the plastic like solid layer of rock beneath the lithosphere. It flows very slowly and allows the tectonic plates to ride on top. • The outer core: Is a dense liquid layer of molten rock (which blocks the S waves). • The inner core is made of solid iron and nickel. Plate Tectonics: The lithosphere is broken into large slabs called plates. These plates move due to convection cells in the mantle • These plates interact with each other at plate boundaries. • There are three different types of boundaries. • Convergent: Plates come together and form subduction zones with ocean crust or mountains with continental crust. • Divergent: Plates are moving apart. This creates ocean ridges, rift valleys. • Transform: Plates move side by side. Earthquakes! • Fault: A break in the Earth’s crust along which blocks of the crust slide relative to one another. • Earthquakes: The vibrations caused by the slippage along these faults. • Richter scale: used to quantify the amount of energy released by an earthquake. • Magnitude: The measure of energy is called. • For each increase of 1 on the scale represents 32 times more energy than the previous number. Where do Earthquakes occur? • Most earthquakes occur at plate boundaries. • About 1 million occur each year but most can’t be felt. • There is a direct relationship between earthquakes and volcanoes. Volcano: A mountain built from magma, that rose from the Earth’s interior to the surface. Local effects of Volcanic Eruptions: • Loss of life • Destruction of property • Loss of income to local economy • Loss of tourism Global Effects of Volcanic Eruptions: • Can cool the earths climate for years due to the ash cloud reducing how much sunlight gets through. • This can reduce the amount of sunlight by 2-4% and can reduce the global temp by nearly a degree. Erosion: The removal and transport of Earth’s surface material. • Weathering: The break down of Earth materials. • Water erosion: Rivers and oceans move millions of tons of sediment each year and dramatically change the landscape over time. Wind Erosion: Wind carries away particles in areas of little vegetation like beaches and deserts. Glaciers: Large moving mass of ice. • This is responsible for most of the lakes in NY. • Creates U shaped valleys. • Can leave large deposits such as Long Island Section 2: The Atmosphere Composition: 78% Nitrogen, 21% Oxygen, 1% other Atmospheric functions: • Allows us to breath. • Insulates the Earth and regulates temperatures • Distributes energy • Protects us from harmful UV rays (ozone layer) Air pressure: Caused by the weight of the ocean of air above us. The higher you go, the less air is on top of you, there for the less air pressure. Layers of the Atmosphere • Troposphere: Layer closest to the Earth’s surface. • This is aka the “Weather sphere” because this is where the storms occur. This layer has the most humidity • Extends to 18 Km • This layer is the most dense • Temperatures decrease with altitude Stratosphere: The layer above the troposphere. • Temperature rises as you increase in elevation. • Contains the ozone layer • Extends from 18 Km to 50 Km Mesosphere: The layer above the Stratosphere. • Extends up to 80 Km • Coldest layer of the atmosphere (-93 C) Thermosphere: The atmospheric layer farthest from the Earth’s surface. • The temperatures go up with altitude due to the nitrogen and oxygen absorbing radiation. • Temps here can reach 2000 C but it wont feel warm to us because the molecules are so far apart. Energy in the Atmosphere Energy can be transferred in 3 ways. 1. Radiation: The transfer of energy across space and in the atmosphere • Ex heat from the Sun, or fire. 2. Conduction: Is the flow of heat from a warmer object to a colder one. 3. Convection: The transfer of energy through fluids (gases or liquids). Heating of the Atmosphere • Solar energy reaches earth as electromagnetic radiation traveling at 186,000 miles/sec • 50% of the solar energy that hits the atm reaches the surface • The other 50% gets absorbed or reflected The Movement of energy in the Atmosphere • Air flows from areas of High pressure to low pressure. • This is caused by differences in temperatures • Hot air rises spreads and sinks as cold air. • These form convection currents. Greenhouse Effect • After sunlight (short waves) hits the earth surface it bounces back as infrared (long waves). • These longer waves can’t penetrate the atmosphere because they are trapped and reradiated back to Earth by the greenhouse gases. The main greenhouse gases are carbon dioxide and methane, water vapor and nitrous oxide. Greenhouse gas sources Section 3: The Hydrosphere and Biosphere The Hydrosphere and Water cycle Water cycle: The continuous movement of water into the air, onto land, and then back to water sources. Evaporation: Is the process by which liquid water is heated by the Sun and rises into the atmosphere as water vapor. Condensation: When water vapor cools and becomes a liquid. Precipitation: When water droplets fall because they are too large to be held up in the cloud. Transpiration: When the water given off by trees and plants evaporates. Earth’s Oceans • World Ocean: The Atlantic, Pacific, Artic, and the Indian oceans are all interconnected. • This covers a little more than 70% of Earths surface. Pacific Ocean • Largest ocean • Deepest point is called Challenger Deep which is at the bottom of the Mariana Trench (11,033 m) • This is deeper than Mt Everest is tall (8,800 m) • James Cameron went down there in a mini sub. Atlantic Ocean • Second largest ocean • ½ the size of the Pacific ocean • Charles Lindberg made famous by becoming the first pilot to make the flight across the Atlantic. Indian ocean • Third Largest ocean Artic Ocean • Smallest ocean • Much of the surface is covered with ice Ocean water • More dense then fresh water due to more salt • Salinity: concentration of dissolved salts it contains Temperature zones • The surface water is warmed by the Sun. • The depths are cold because sunlight cant reach. • Thermocline: Depth of 300 M to 700 m where the temp decreases rapidly with depth. A Global temperature regulator: • The oceans absorb and store energy from sunlight. • This regulates temps in the atmosphere. • The Worlds ocean absorbs over 50% of the radiation that reaches the surface. • Cities near the ocean have milder annual temps Water has a higher specific heat than land. • Water takes a long time to heat up and a long time to cool down. • This helps regulate the temps in the atm as well. • Without the oceans, the temps on Earth would be too extreme for life to survive. Ocean currents • Currents are created by wind, differences in temp and density. • Currents redistribute heat throughout the oceans. • If currents like the North Atlantic drift were to shut down it could throw Europe into an ice age. Fresh Water • About 3% Of all of the water on Earth is fresh. • 90% of that 3% is locked away in the ice caps. • Most of the useable fresh water is underground River Systems or water sheds • A network of streams and rivers that drains an area of land. • Tributaries: are smaller streams and rivers that flow into larger ones. • The Mississippi is the largest water shed in the contiguous United States. Ground Water • When water infiltrates the ground it becomes ground water. • Aquifer: A rock layer that stores and allows the flow of ground water. • Recharge zone: The surface of the land where water enters the aquifer. Biosphere: The Narrow layer around Earth where life can exist. Requirements for life: 1. Water 2. Temps between 0 and 40 degrees C 1. Source of energy Most life is near the Earths surface because this is where the sunlight is. Energy Flow in the Biosphere • Energy from the Sun is constantly being added to the biosphere but matter is not. Food chain • When an organism dies, its body is used by other organisms for substance. When the top predators die, their bodies are broken down by fungus and its nutrients become available for other organisms to use. Closed system: Energy enters the environment, but mater does not. The Earth is mostly a closed system. Open system: Both mater and energy are exchanged between a system and the surrounding environment. The early Earth was hit frequently with comets and meteorites, so was more open than it is today.