Ice Age Ice Age, a time when ice sheets and alpine glaciers were EXTENSIVE, and advanced and receded repeatedly over LONG PERIODS of time.

During the last Ice ager, How much of the earth was covered with ice? About 1/3rd

Ice Age There is more than one “ice age”. As far back as 2 billion years ago (snowball earth) Most recent “Ice Age” began 2 million years ago and ended about 15,000 years ago. The last ice age, called the “Wisconsin” episode was during the Pleistocene epoch and about half of Illinois was covered

Evidence: moraines, erratics

Effects: What happened to the Mississippi River? Where did the Illinois River come from?

The Great Lakes

Causes of the Ice Age The Earth is a dynamic planet – it is constantly changing. In what ways? The Earth System is part of a larger system (solar system) Earths has 4 spheres (hydrosphere, geosphere, atmosphere, biosphere). How have each of them contributed to the Ice Age? What processes warm the Earth and prevent us from being in a continuous Ice Age? What factors could trigger the onset of an Ice Age?

Ice Ages: groups white boards Brainstorm and list several possible factors that may have caused the ice ages: Combine ideas onto board. Write a questions for each possible cause Divide the questions within your group. Research and answer the questions on the boards

Causes of the Ice Age (page 331) 1.Planetary System and Earth’s position 1.Orbit and distance from the sun (eccentricity, perihelion/aphelion) 2.Tilt (precession) 2.Plate Tectonics: shifting landmasses (Pangaea) 3.Atmosphere gases (greenhouse effect) 4.Hydrosphere 1.ocean currents and climate 2.ocean level changes) 5.Geosphere: Volcanic Eruptions, Mountains and Albedo 6.Biosphere: Population growth/extinction 1.Contribution to Greenhouse gases

Earth’s Orbit Eccentricity: elliptical orbit. the distance to the Sun at perihelion is only about 3% less than its distance at aphelion. –We are farthest on _________ –We are closest on __________ The eccentricity of the Earth's orbit (how elliptical it is) also changes over very long periods of time, about 100,000 years from almost zero (circular orbit) to about three times its current value.

Earth’s Motion Obliquity: tilt on it’s axis –between ° –Varies every 41,000 yrs –The greater the tilt, the more extreme the seasons Precession: “wobbles” as it rotates –Every 21,000 yrs. So… when the earth is at its extreme tilt and farthest from the sun it its orbit, then we experience extreme “cold spells”

Plate Tectonics: Pangaea Due to plate tectonics, land masses have moved. We were closer to the poles and farther from the equator at different times Pangaea, 250 mya Evidence: –Coal beds in Antarctica –Glacial features in Africa and India

Atmosphere CO 2 (greenhouse gasses) in the have fluctuated. Increase CO 2 causes global warming Decrease CO 2 causes global cooling

Shifting land masses changed ocean currents. Circulation of warm and cold ocean currents is blocked 1.Plate Tectonics: shifting landmasses 1.Pangaea 2.Mountain building and albedo 3.Volcanic eruptions 4.Ocean Currents

How do Ocean Level Change during Ice Ages?

Geosphere Mountains have snowy tops with Albedo: the amount of solar energy absorbed by the Earth’s surface. White snow reflects (90%) of Sun’s energy = colder temperatures = more snow = even less energy absorbed etc. Volcanoes and Atmospheric Gases

Plate tectonics (convergent plates) create mountains that have high elevations producing snow and glaciers.

How do the following affect CO 2? Population Increases

Mass Extinctions

On a sheet of paper: True or False? _____ 1. Glaciers are only at the north and south poles. _____ 2. A glacier is solid ice. _____3. Antarctica is covered by a glacier. _____4. There could never be a glacier at the equator. _____5. All glaciers move. _____6. Glaciers flatten the land. _____7. When glaciers melt they back up. _____8. Glaciers can carve out valleys. _____9. The Great Lakes were formed by glaciers _____ 10. There has been one Ice Age.

Glacier Quiz! y/physical_geography/glaciers.htmlhttp:// y/physical_geography/glaciers.html

Research List many, many, many things that you see that relate to glaciers, and ice age Write questions that you have. Question “bad science” List “good science” Select ONE to research. Write a research QUESTION One page (with pictures) One source