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Glacial Geology of Northeast Pennsylvania

Glacial Geology of Northeast Pennsylvania. How do we know they were here?. Geologic forensics…look for the evidence… …and an 800 pound gorilla leaves a lot of evidence!. Glacial grooves and striations. Chatter marks. Characteristic landforms, e.g., horns. Kettle lakes on an outwash plain.

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Glacial Geology of Northeast Pennsylvania

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  1. Glacial GeologyofNortheast Pennsylvania

  2. How do we know they were here? Geologic forensics…look for the evidence… …and an 800 pound gorilla leaves a lot of evidence!

  3. Glacial grooves and striations

  4. Chatter marks

  5. Characteristic landforms, e.g., horns

  6. Kettle lakes on an outwash plain

  7. Does this look familiar? The world famous Archbald Pothole!

  8. Terminal moraines

  9. Medial and lateral moraines

  10. Characteristic deposits, e.g., till

  11. Continental Glacier in Antarctica

  12. An empty cylinder with a capped hole near the base was filled with water and then removed and the cylinder of ice was frozen. The cap over the hole was subjected to pressure.

  13. A Typical Glacial Advance and Retreat

  14. Ice Ages • Pleistocene 3 M.y. • Permian 250-220 M.y. • Ordovician 450 M.y. • Precambrian • 900-650 M.y. (Snowball Earth) • 2300 M.y.

  15. What Causes Ice Ages? Within Earth • Carbonate-Silicate Cycle • Volcanic eruptions - Sudden output of CO2 (warming) or particulates (cooling) • Mountain building - Changes in atmospheric circulation • Continent-Ocean configuration Outside Earth • Changes in sun (faint early sun) • Variations in Earth orbit (Milankovitch Cycles)

  16. Is This What Pennsylvania Looked Like?

  17. Till Shadow

  18. Beaded valleys

  19. Are We Headed For Another Ice Age? • Heating & cooling in historic times • Smoke, haze, CO2 may alter climate • Global warming due to fossil fuels may be catastrophic in many ways, but will probably not much affect these longer-term cycles. We will have run out of fossil fuels long before the duration of a typical interglacial. YES!!

  20. Glacial Facts • Presently, 10% of land area is covered with glaciers. • Glaciers store about 75% of the world's freshwater. • Antarctic ice is over 4,200 meters thick in some areas. • In the US, glaciers cover > 75,000 km2, with most located in Alaska. • During the last Ice Age, glaciers covered 32% of the total land area. • If all land ice melted, sea level would rise approximately 70 meters worldwide. • The land underneath parts of the West Antarctic Ice Sheet may be up to 2.5 kilometers below sea level, due to the weight of the ice. • The Kutiah Glacier in Pakistan holds the record for the fastest glacial surge. In 1953, it raced more than 12 kilometers in three months, averaging about 112 meters per day. • The Antarctic ice sheet has been in existence for at least 40 million years. • From the 17th to late 19th century, the world experienced a "Little Ice Age," when temperatures were consistently cool enough for significant glacier advances.

  21. Pleistocene ice sheet at maximum extent

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