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Transcript
The Dynamic Earth Chapter 3 The Earth as a System • The Earth is an integrated system – Geosphere - rock, soil and sediments – Atmosphere - the air we breathe – Hydrosphere - All of the water on or near the earth’s surface – Biosphere - part of the earth where life exists • 9km above the earth’s surface to the bottom of the ocean 1 The Geosphere 2 The Earth’s Interior • Seismic waves - the waves that travel through the interior of the earth during an earthquake. • Seismic waves are used in order to determine the make up of the Earth’ interior – Measure the speed and direction of the waves. – The waves change depending on the type of material it passes through 3 The Composition of the Earth • Three layers based on the composition of each layer • Made up of three layers that get progressively denser • Crust – – – – – Thin outer layer Light elements Less than 1% of the planet’s mass 5-8km thick beneath the oceans 20-70km thick beneath the continents The Composition of the Earth • Mantle – Layer beneath the crust – 64% the mass of the earth – 2,900km thick – Rocks of medium density • Core – Densest elements – 3,400km thick 4 The Structure of the Earth • The Earth can be divided into five layers based on the physical properties of each layer. • Lithosphere – Outer layer – Cool, rigid layer – 15-300km thick and includes the crust and upper mantle – Divided into tectonic plates 5 The Structure of the Earth • Asthenosphere – – – – Beneath the lithosphere 250km thick Solid layer of the mantle that flows very slowly. Tectonic plates move on top of it. • Mesophere – The lower part of the mantle – 2,550km thick • Outer core – Dense liquid layer made up of iron and nickel – 2,200km thick • Inner core – Dense and solid iron and nickel – 1,228km thick 6 Plate Tectonics • Tectonic plates – Part of the lithosphere – Glide across the asthenosphere – Continents move with them 7 Plate Boundaries • Plate boundaries are regions of geologic activity – Mountains form – Earthquakes occur – Volcanoes erupt Plate Tectonics and Mountain Building • Plates colliding causes the formation of mountains • Example-Himalayas formed from the collision of the Asian and Indian Plates 8 Earthquakes • Fault - break in the Earth’s crust along plate boundaries. • Plate boundaries slip past each other • When rocks break as the plates slip earthquakes occur. • Most active earthquake zones occur along plate boundaries • Richter scale - Quantifies the amount of energy released by an earthquake Earthquakes • Magnitude - the measure of energy released by an earthquake. • Smallest magnitude - 2.0 • Largest magnitude - 9.5 • Each magnitude is 31.7 times more energy than the number below it. • Example - a magnitude of 6 releases 31.7 times more energy than a magnitude of 5 9 Volcanoes • Volcano - mountain built from magma that rises form the Earth’s interior to the surface • Can occur in land or under the sea. • Most occur along tectonic plate boundaries. 10 Volcanoes • Local effects – – – – Human loss Buildings collapse Bury crops Health problems - difficulty breathing • Global effects – Ash and gas reduces the amount of sunlight that reaches the earth. – Change the Earth’s climate for years by causing a drop in the global temperature 11 Erosion • Erosion - The removal and transport of surface material • Erosion is caused by wind and water • Erosion wears down rocks and makes them smoother. • Erosion moves soil The Atmosphere 12 Composition of the Atmosphere • Atmosphere - the mixture of gases which surrounds the Earth • Nitrogen makes up 78% of the gases. – Enters the atmosphere when volcanoes erupt and dead animals and plants decay. • Oxygen makes up 21% of the gases – Primarily produced by plants Air Pressure • Gravity pulls the atmosphere towards the Earth’s surface • The atmosphere is 30km from the ground • The atmosphere is denser near the Earth’s surface 13 Layers of the Atmosphere • Layers of the atmosphere based on temperature changes. • Troposphere – – – – – Nearest the Earth’s surface Extends 18km Almost all weather occurs in this layer. Densest layer Temperature decreases as altitude increases 14 Layers of the Atmosphere • Stratosphere – Above the troposphere – Between 18-50km – Temperature rises as altitude increases due to the absorption of UV rays by the ozone. – Ozone - Absorbs ultraviolet readiation which can damage living cells Layers of the Atmosphere • Mesophere – Between 50-80km. – Coldest layer - as low as -93°C • Thermosphere – – – – Nitrogen and Oxygen absorb solar radiation. Temperatures as high as 2,000°C Air is very thin Lower thermosphere absorbs x-rays and gamma rays resulting in the formation of ions – Ionosphere - the lower thermosphere – Sometimes these ions radiate the energy as light. 15 Energy in the Atmosphere • Energy from the sun is transferred in Earth’s atmosphere – Radiation - transfer of energy across space and in the atmosphere – Conduction - flow if heat from a warmer object to a colder object when they are in contact with each other. – Convection - transfer of heat by air currents. • Hot air rises and cold air sinks 16 Heating of the Atmosphere • The Earth only receives about two billionths of the energy from the sun • The energy which does reach the earth is tremendous • About half of the solar energy reaches the surface of the Earth • The rest of the energy is absorbed or reflected by clouds, gases, dust or the earth’s surface. 17 Movement of Energy in the Atmosphere • Warm air rises in the troposphere and cold air sinks. • Convection currents - The process of warming and cooling. • Creates winds • Distributes heat around the Earth. 18 Greenhouse Effect • Sunlight heats the surface of the earth. • Some of the heat is reflected back into the atmosphere and escapes into space • Some of the heat is reflected back into the atmosphere and is trapped by greenhouse gases. • Greenhouse Effect - Gases trap heat near the surface of the Earth • Greenhouse gasses - carbon dioxide, methane, and nitrous oxide, water vapor Greenhouse Effect • Without the greenhouse effect the Earth would be too cold for life 19 Hydrosphere and Biosphere Hydropshere and the Water Cycle • Hydrosphere - all of the water on or near the Earth’s surface • Water cycle - the movement of water into the air, onto land and then back to the water. 20 Hydropshere and the Water Cycle • Evaporation - liquid water is heated by the sun and then rises into the atmosphere as water vapor • Condensation - water vapor forms water droplets • Precipitation - large water droplets which fall from the clouds. Earth’s Oceans • World ocean - single, large interconnected body of water. • Covers 70% of the Earth’s surface • Regulates the Earth’s climate • Largest - Pacific • Atlantic • Indian • Arctic - Smallest 21 Earth’s Oceans Ocean Water • Ocean water contains salt • NaCl makes up more than 85% of the salt • Salinity - total quantity of dissolved salts • Average salinity is 3.5% by weight • Salinity can vary by location. – Rain, evaporation, fresh water 22 Temperature Zones • Surface zone – warmed by the sun • Thermocline – Boundary between the warm and cold water – Temperature falls rapidly with depth • Deep zone – Below the thermocline – Very cold 23 Global Temperature Regulator • The ocean absorbs and stores over 50% of heat from the sun • Absorbs and releases heat more slowly than the land • Regulates the temperature of the atmosphere • Ocean currents transports heat around the globe 24 Ocean Currents • Currents - movement of water that occur at or near the ocean surface. • Currents are driven by global wind patterns • Currents influence the climate of the land areas they flow past • Deep currents – Cold water sinks near the poles and flows toward the equator. 25 Fresh Water • 2% of all of the water is fresh water • Most is locked in ice caps and glaciers • The remainder is found in lakes, rivers, wetlands, soil, rock, and the atmosphere. • River systems - network of streams that drains an area of land Groundwater • Groundwater - water that seeps into the ground • Less than 1% of all water on the Earth. • Aquifers - Rock layer that stores and allows the flow of groundwater. • Recharge zone - surface of the land where water enters the aquifer 26 27 The Biosphere • Biosphere - the narrow layer around the Earth’s surface where life can exist. • 9km above the earth’s surface to the bottom of the ocean • Life exists because – Liquid water – Moderate temperatures – Energy from the sun Energy Flow in the Biosphere • Closed system - energy enters the environment but matter does not • Earth is a closed system for matter but an open system for energy from the sun • Plants make food from sun energy, animals eat the plants, animals eat animals. • Energy is lost at each step in the food chain. – Activities of the organism – Heat 28