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Geologic Time

Geologic Time. “ Nothing hurries geology ” - Mark Twain. What is Time?. Time is how we sense and record changes in the environment. It is our sense of one thing happening after another. We need standards of time for the convenience of everyday life. Units of time.

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Geologic Time

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  1. Geologic Time “Nothing hurries geology” - Mark Twain

  2. What is Time? • Time is how we sense and record • changes in the environment. • It is our sense of one thing happening after another. • We need standards of time for the convenience of everyday life.

  3. Units of time • As humans we think of time related to personal experience. • Seconds • Minutes • Hours • Month • Years • Decades • Centuries • Millenia However, you will see that when we talk about Earth history, even using a millennium isn’t sufficient because of Earth’s vast age.

  4. Deep Time • When we study history 200, 1,000 or even 2,000 years seems like a long time. • Geology involves vastly greater amounts of time • This is referred to as deep time.

  5. Geologic Processes • Most are slow but relentless • Reflecting the pace at which the heat engines work • It’s unlikely that a mountain will visibly change shape or height during a human lifetime

  6. Geologic Processes • In a geologic time frame • Most mountains are probably eroding “rapidly” Uluru is a great block of uptilted sandstone in the heart of Australia's Outback. This region may be the world's best-developed peneplain, and Uluru its best-known monadnock.

  7. To a geologist . . . • “Rapidly” may mean within a few million years. • A “fast” process • Started and completed within a few million years. • For example . . .

  8. Rate of Plate Motion • At a mid ocean ridge • 1 cm/yr movement • 100,000 years for the seafloor to move 1,000 km (100,000 cm in one km)

  9. Some geologic processes do occur quickly Mt. St. Helens

  10. Landslides Occur Quickly • Tully Valley landslide on April 27, 1993 • Occurred after heavy precipitation of • 190 mm (7.5 in) during April in conjunction • with melting of a winter snowpack

  11. Processes of Change Through time

  12. Spatial Scales of Observation • Geologists study all of Earth’s materials from: • The spatial scale of atoms • To the scale of our planet (global scale)

  13. Spatial Scales of Observation • Geologists study all of Earth’s materials from: • The spatial scale of atoms

  14. Spatial Scales of Observation • Geologists study all of Earth’s materials from: • The spatial scale of atoms

  15. Spatial Scales of Observation • Geologists study all of Earth’s materials from: • The spatial scale of atoms • To the scale of our planet (global scale)

  16. Global Perspective of Earth

  17. Thickness on the model is calculated using a proportion. 119 mm X 6371 km 16 km (6371 km) X = (119 mm)(16 km) X = (119 mm)(16 km) 6371 km X = 0.3 mm • On this scale: • Mt. Everest (8.8 km or 5.5. mi.) • would be 0.16 mm high. • Deepest location in the ocean • (Mariana Trench – 10.9 km or • 6.8 mi) would be 0.2 mm deep

  18. The Geologic Time Scale • Earth history is subdivided into time units based on: • The fossil record • Extinctions

  19. Geologic Time Scale – Temporal Scales of Observation • Like in a book, events and relationships are grouped into • Paragraphs • Sections • Parts • These are the geologic time scale’s • Eons • Eras • Periods • Epochs • The “calendar” into which geologic events are placed. Phanerozoic

  20. Temporal Scales of Observation • Grand Canyon, AZ • Exposed rocks at the bottom of the canyon are more than a billion years old • Sediments in the Colorado River • May have formed just seconds ago

  21. Scale Model of Earth History

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