Advanced Earth Science (Ch. 11) Atmospheric Basics

Origin & Evolution of the Atmosphere Changes Over Time (VA SOL ES. 11 a & b)

First Earth’s First Atmosphere Temperature’s too high to support life Composed of mainly Hydrogen and Helium

Early Earth’s Early Atmosphere Developed billions of years ago from volcanic eruptions (called outgassing) No oxygen – would have been extremely toxic to breathe Our early atmosphere consisted mostly of nitrogen (N), Carbon Dioxide (CO 2 ) and water vapor (that eventually formed the oceans)

Life’s Role on the Atmosphere As early oceans began developing blue- green algae began to form Blue-green algae (called CYANOBACTERIA) take up CO 2 and release O 2 through photosynthesis Over time oxygen levels rose enough to support animal life.

How do we know? Deep ice cores record past atmospheric composition The deeper the cores are, the richer they were in CO 2

Red Beds Layers of iron that have oxidized (rusted) due to presence of oxygen Confirmed that oxygen was present millions of years ago

Today Earth’s Atmosphere Today 78% Nitrogen 21% Oxygen 1% Other Argon 0.93% Carbon Dioxide 0.03% Water Vapor 0.03 Trace Gases 0.01%

Atmospheric Pressure Air has mass and pushes down on us all the time We have 15lbs/in 2 pushing down on us at all times (sea level) As you go higher in the atmosphere, pressure decreases Force of gravity is strongest at Earth’s surface and decreases as you increase altitude

Structure of the Atmosphere Earth’s atmosphere is composed of four layers: Troposphere Stratosphere Mesosphere Thermosphere/Exosphere Each layer differs in: Temperature Altitude Pressure Gas Composition

Troposphere 1 st layer of the atmosphere Weather occurs here Temperature as altitude Altitude: 5-10 km Composition: 78% N 21% O 2 1% Trace Gases

Tropopause The very top layer of the troposphere that separates it from the stratosphere

Stratosphere 2 nd layer of the atmosphere No weather Reason why planes fly in the lower portion of the stratosphere Temperatures as altitude Altitude:10-50 km Composition: Ozone (O3)

Stratopause The very top layer of the stratosphere that separates it from the mesosphere

OZONE Causes the temperature in the stratosphere to increase Ozone layer km Ozone absorbs radiation from the sun and protects us from its UV rays that can cause anything from sunburn to cancer. Scientists believe human activities are depleting the ozone layer Nitric Oxide given off from jet exhaust Chlorofluorocarbons (CFC’s) used in refrigerants CFC’s have been banned because of its link to ozone depletion

Mesosphere 3 rd layer of the atmosphere Layer where many meteors burn up in the atmosphere Temperature as altitude Does not absorb solar radiation Altitude: km Composition: N and O 2 ions

Mesopause The very top layer of the mesosphere that separates it form the thermospshere

Thermosphere 4 th layer of the atmosphere Region of the atmosphere where the aurorae occur Temperature as altitude Solar radiation first hits the Earth’s atmosphere and heats it. Altitude: 80 km to thousands of km before it reaches space Composition: Ions and free floating electrons

Exosphere Outermost layer of the Earth’s atmosphere Satellites can orbit in this layer Composition: Hydrogen and Helium Above the exosphere is outer space There is no clear boundary between the atmosphere and space

Atmospheric Regulation Conduction, Convection, Radiation (VA SOL ES. 11c)

Radiation Transfer of heat energy through empty space Electromagnetic waves travel through space and come in contact with an object which transfers heat to that object

15% absorbed by atmosphere 25% Incoming Solar Radiation 100% 6%4% Reflected by Atmosphere Reflected by clouds 50% Absorbed at Surface Reflected from Surface

Conduction The transfer of heat between substances that are in direct contact with each other.

Convection The transfer of energy by the flow of liquids or gas As a gas or liquid is heated it warms, expands, and rises because it is less dense. As a gas or liquid cools it becomes more dense and falls. This process creates a convection current. This is the primary method by which heat moves through gasses and liquids