Modified by A. Brewer original by Eryn Sutliff Earth’s Atmosphere Modified by A. Brewer original by Eryn Sutliff
How our atmosphere evolved The early atmosphere did not support life. It contained deadly gases such as Methane and Ammonia. There was very little Oxygen. Over time, gases were added to the atmosphere by volcanic eruptions, and as a result of chemical reactions due to sunlight.
How our atmosphere evolved cont. The OZONE LAYER formed as a result of the chemical reactions. Ozone is made of three oxygen atoms bonded together. It blocks out ultraviolet radiation from the sun. The formation of the ozone layer allowed MICRO-ORGANISMS such as Blue-Green Algae to appear on earth. They take in carbon dioxide and release oxygen, so the amount of OXYGEN in the atmosphere steadily increased.
How our atmosphere evolved continued… Stromatolites were some of the early organisms that used Photosynthesis to convert CO2 into Oxygen. They still exist today and have survived 5 mass extinctions!
Today’s atmosphere
Layers of the Atmosphere
Basis for Layers Layers are based on TEMPERATURE CHANGE within the layer. As you move up through the troposphere, temperature decreases. As you move up through stratosphere, temperature increases. As you move up through the mesosphere, temperature decreases As you move up through the thermosphere, temperature increases.
Temperature/Density and the Troposphere Troposphere: temperature at surface is warmed by the earth absorbing energy from the sun. Convection currents carry the heat upward, so the air cools as it rises. Density decreases since there is less air above.
The Stratosphere “Strato” means layer or spreading out Contains the ozone layer which absorbs energy and causes the temperature to rise. The ozone layer protects the surface from dangerous UV rays (ultraviolet radiation from the Sun).
Temperature and the Stratosphere Ozone, made of oxygen, absorbs ultraviolet radiation from the sun, causing the temperature to increase.
The Mesosphere Drop in temperature marks beginning of mesosphere “Meso” means middle Most meteors burn up here
The Thermosphere “Thermo” means heat, Very hot (over 1000°C), but since air is so thin (not very dense) it would not feel warm at all. The space shuttle orbits here. So even though it is very hot (over 1000°C), it would feel cold because there are so few particles to transfer heat to you. Solar radiation first hits this layer, so the few particles that are here can gain lots of energy. They move rapidly, so they have a very high temperature.
The Exosphere “Exo” means outer Extends for 1000’s of miles Satellites orbit here No definite edge Molecules gradually escape out into space
Aurora Borealis A glow in the night sky produced in the upper atmosphere by ionized particles from the solar wind interacting with Earth’s magnetic field.
Transfer of Heat Heat can move in three ways: 1- Conduction: Heat is transferred through direct contact. 2- Convection: Heat is transferred by a hot fluid (gas or liquid) circulating or moving. 3- Radiation: Heat is transferred by electromagnetic waves.
If a metal cooking fork is left in the fire long enough, eventually the end we are holding will become too hot for us to handle. Heat was transferred from the flames in the campfire to the metal fork, and then from molecule to molecule in the fork until it reaches our fingers via conduction. .
What is Convection? Density differences in temperatures cause heat to rise and cool to sink, this applies to gasses and liquids Examples: Heated water becomes less dense and rises, Boiling water Hot air expands and is less dense hot air balloon
Imagine standing in front of a camp fire and holding out your hands in front of you…what do you feel? Warmth as your hands absorb the radiation coming from the fire.
Heat moves into our atmosphere through SOLAR RADIATION (Insolation)
Heat moves throughout (within) our atmosphere in CONVECTION CURRENTS
Heat Transfer Quiz: Identify the type of Heat Transfer C B A A = Radiation B = Convection C = Conduction