Earth’s Atmosphere

Part 1 - A view of Planet Earth: Spheres Within a Sphere

1

The Size of the Earth Diameter (N to S):

12,740 km Circumference (distance

around the Earth) at the equator: 40,075 km

Equator: imaginary line around the Earth that divides Earth into two hemispheres, Northern and Southern

Hemisphere = half a sphere2

Three Main Features of the EarthLithosphere:

All the land on Earth the crust Includes the

continents and all the land beneath the oceans and the continents

Atmosphere: Envelope of gases

that surrounds the Earth

Provides materials necessary to support life

Protects the Earth

Hydrosphere: All the water on Earth Includes oceans,

rivers, streams, lakes, ponds, etc., the water frozen in glaciers and at the poles, and water in underground aquifers

97% is salt water 85% of the fresh

water is frozen in the polar ice caps leaving only 15% of the 3% available for use

3

Earth’s Atmosphere

Part 2 – Development of the Atmosphere

4

The Past Atmosphere Theory: 4 billion years ago

the atmosphere contained two deadly gases, methane (CH4) and ammonia (NH3), and also some water

Sunlight triggered chemical reactions forming new materials: nitrogen, hydrogen, and carbon dioxide.

Methane and ammonia were removed but water remained.

The hydrogen dissipated into space.5

The Past Atmosphere When cyanobacteria

evolved they began releasing oxygen into the atmosphere as a by-product of photosynthesis.

Some O2 molecules rose to the stratosphere where sunlight caused them to be converted into ozone (O3).

The ozone layer (at 30km above the Earth’s surface) protects life on Earth by absorbing most of the harmful UV radiation from the sun.

6

The Past Atmosphere In time, green algae

and plants also began to release oxygen into the atmosphere.

Around 600 million years ago the amounts of oxygen and carbon dioxide stabilized to their present levels.

7

The Present AtmosphereComposition of dry atmosphere:

Nitrogen ~ 78% Oxygen ~ 21% Argon ~ .9% All other gases, including the

greenhouse gases carbon dioxide and methane, <0.04%

Water Vapor ~0.40% over full atmosphere typically 1% – 4% at surface

8

The Present Atmosphere

9

In addition to all the gases that make up the atmosphere there are also tiny particles of solid materials.

These may include dust, smoke, dirt, and bits of salt.

Mold spores and pollen can also be found at varying levels through the year.

Sources may be natural (volcanoes for example) or artificial (industrial pollutants).

Oxygen Used by all

organisms that carry out aerobic respiration.

Released by plants as they carry out photosynthesis.

Also needed in order for things to burn (combustion) and rust (oxidation).

Oxygen does cycle in and out of the atmosphere, but it is not a limiting factor for the growth of organisms, nor are high levels a concern.

10

Atmospheric Cycles Cycles are used by scientists to describe how

substances naturally enter and leave the atmosphere.

Three cycles that are important to organisms are: The Nitrogen Cycle The Carbon Cycle The Water Cycle

11

Nitrogen View the following animation on the Nitrogen

Cycle:http://moodle.oakland.k12.mi.us/os/mod/page/view.php?id=37546&inpopup=1

Major Points to the Nitrogen Cycle: All living things need nitrogen to make proteins

and nucleic acids (DNA and RNA). N2 gas in the atmosphere can’t be used by

most organisms. Certain bacteria that live in symbiotic

relationships with plants, or that live in the soil, can “fix” N2, converting it into NH3 that can be used by plants or be converted to NO3 that can be used. (= nitrogen fixation)12

NitrogenMajor Points to the Nitrogen Cycle (continued): Animals get nitrogen by eating plants, or other animals When organisms die and their bodies decompose, most

of the organic compounds are changed back into inorganic compounds, including NH3, NO3, and NO2. These compounds can then be taken up by plants and reused.

Certain bacteria in the soil change some of these compounds back into nitrogen gas (N2) that is released back into the atmosphere. (= denitrification)

FYI: In an energy consuming process, humans artificially convert N2 into NH3 and NO3 to make fertilizer. Overuse of fertilizer can alter the natural nitrogen cycle and change the growth of organisms in an area.

13

Assignment Working with a partner, create a labeled

diagram of the nitrogen cycle. Use your notes about the major points to the

nitrogen cycle as a guide for what to include. Use arrows to show the direction of movement of

nitrogen. Use illustrations where helpful.

14

The Nitrogen Cycle

15

Carbon

Major Points to the Carbon Cycle Present as carbon dioxide in the atmosphere Used by plants to make organic compounds during

photosynthesis Absorbed by ocean waters, where it is used by

phytoplankton for photosynthesis Produced by all organisms during the process of

respiration (including water dwellers) Released when organic compounds decompose or are

burned

View the following animation on the carbon cycle:http://moodle.oakland.k12.mi.us/os/mod/page/view.php?id=37546&inpopup=1

16

AssignmentWorking with a partner, create a labeled diagram of the carbon cycle.

Use your notes about the major points to the carbon cycle as a guide for what to include.

Use arrows to show the direction of movement of carbon.

Use illustrations where helpful.

17

THE CARBON CYCLE: This diagram of the fast carbon cycle shows the movement of carbon between land, atmosphere, and oceans. Yellow numbers are natural fluxes, and red are human contributions in gigatons of carbon per year. White numbers indicate stored carbon. (Diagram adapted from U.S. DOE, Biological and Environmental Research Information System.)

18

Water

Major Points to the Water Cycle The evaporation and precipitation of water drive the

cycling of water across the Earth. The most evaporation occurs over the ocean. Most water evaporated from the ocean forms clouds

(condensation) and then precipitates back into the ocean.

Some water vapor is blown over land where it then condenses into clouds and precipitates on to the land.

View the following animation on the water or hydrological cycle: http://moodle.oakland.k12.mi.us/os/mod/page/view.php?id=37546&inpopup=1

19

Water

Major Points to the Water Cycle…continued Evaporation also occurs from lakes and rivers and

from the soil. Plants also release water into the air by

transpiration (the evaporation of water taken up by roots and transported to the leaves).

Some water that precipitates is absorbed by the ground and can be used by plants. Some becomes runoff and flows into streams, rivers, ponds, and lakes.

Some water eventually flows back to the oceans.

20

AssignmentWorking with a partner, create a labeled diagram of the water cycle.

Use your notes about the major points to the water cycle as a guide for what to include.

Use arrows to show the direction of movement of water.

Use the appropriate labels for each part of the cycle.

Use illustrations where helpful.

21

22