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Ruby Mountains, Nevada

Ruby Mountains, Nevada. Regional Metamorphism in the Jurassic.

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Ruby Mountains, Nevada

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  1. Ruby Mountains, Nevada Regional Metamorphism in the Jurassic

  2. In the Jurassic, a subduction zone formed along western North America. This caused a lot of compression which formed a range of mountains. These are called the Nevadan mountains. There was a lot of regional metamorphism in the Nevadan mountains. Later, the mountains eroded away, but the metamorphic rocks that formed the core of these mountains remained under ground. About 5-10 million years ago, this metamorphic core was uplifted, forming the Ruby mountains. So, the Ruby mountains are the core of the ancient Nevadan mountains. There are many garnets in these metamorphic rocks, and the early discoverers called the mountain range, the Ruby mountains. They must have mistakenly thought that the garnets were rubies. Nevadan Mountains in the Jurassic

  3. review Important announcement regarding extra-credit quizzes According to the syllabus, a maximum of 20 extra credit points can be added to your score. Some of you have already come close to 20 extra credit points (congratulations!) Please continue to take quizzes, after you have reached your 20 point maximum BECAUSE: If we do decide to curve grades at the end of the semester, I will do so only by allowing additional extra credit points (above and beyond the 20 maximum)to be added to your final grade.

  4. review • Important notes about extra credit quizzes • On the electronic sheets, you must write AND bubble in your correct posting ID to get credit. • When filling in your posting ID, you fill your numbers in FROM THE LEFT. No hyphens or spaces. • Some people have the same ID number on their ID card twice- in that case, your Posting ID does NOT follow the formula. Ex: If your two numbers are 1000876543 and 1000876543, your posting ID will NOT be 6543-543! • If you still don’t know your posting ID, you can find it at the following site: • 1) Log in to MyASU • 2) Go to the MyProfile tab • 3) Scroll down to >IDs • 4) Click the link to display your ID information • 5) Find your Posting ID

  5. review The Great Permian-Triassic Extinction (245 Million years ago) • 90-95% of all species disappeared from the fossil record! • This is the greatest extinction known; much larger than that associated with the death of the dinosaurs (which occurs later). • Geologists are unsure of what caused this extinction, but it is thought to have been caused by either: • Formation of Pangea • Reduced continental shelf (shallow sea regions off the coast) • Large landmass leads to harsh climates in interior regions • Massive flood basalt volcanism that occurred in Siberia • A meteorite impact?

  6. review Mesozoic Era (245-65 million years ago) – Age of the Dinosaurs Triassic Period (245-208 million years ago) Dinosaurs first appear First mammals – small and probably nocturnal

  7. review Ron Blakey (NAU)

  8. review Mesozoic Era (245-65 million years ago) – Age of the Dinosaurs Jurassic Period (208-144 million years ago) Stegosaurus and Sauropods appear The first feathered bird-like reptile Archaeopteryx appears (perhaps the ancestor of birds!)

  9. Pangea begins to break apart – the Atlantic ocean is first formed.

  10. Ron Blakey (NAU)

  11. Mesozoic Era (245-65 million years ago) – Age of the Dinosaurs Cretaceous Period (144-65 million years ago) Tyrannosaurus Rex and Triceratops appear The first flowering plants appear The Rocky Mountains start to form

  12. Ron Blakey (NAU)

  13. The Cretaceous-Tertiary Extinction (also called the K-T Extinction) Dinosaurs, and most plankton and plant species became extinct In recent years, there has been an abundance of evidence supporting the hypothesis that a large asteroid caused this extinction.

  14. An impact site of the same age as the extinction was found on the Yucatan Peninsula in Mexico. This is called the Chicxulub crator. Geophysical evidence of impact crater

  15. Ron Blakey (NAU)

  16. Cenozoic Era (65 million years ago until today) – Age of the Mammals Tertiary and Quaternary Periods • Some reptiles survived the K-T extinction (crocodiles, alligators, turtles, and lizards). • Mammals rapidly diversify • Increase in size • Increase in brain capacity • Specialization of teeth and limbs • Birds rapidly diversify • Grasses become widespread plants, and large grazing mammals appear • First Hominids (4 million years ago)

  17. (don’t worry about these animal names) But do know that Wooly Mammoths were around in the Cenozoic.

  18. India drifts toward Asia Africa and Italy drift towards Europe The Rocky Mountains are finishing up

  19. The Alps and Himalayas begin to Form

  20. The last ice ages

  21. Ron Blakey (NAU)

  22. Based on current plate velocities, we can guess at possible future arrangement of the plates. (This is only a rough guess)

  23. Based on current plate velocities, we can guess at possible future arrangement of the plates. (This is only a rough guess)

  24. Based on current plate velocities, we can guess at possible future arrangement of the plates. (This is only a rough guess)

  25. For the exam, you must know all of the information listed on the slides • (unless otherwise stated), but not all of the dates. Here are the dates that you need to know: • 4.6 Byr – age of the Earth, beginning of the Hadean Eon • 3.8 Byr – first possible evidence for bacteria • 3.5 Byr – stromatolites, first credible evidence of life (bacteria) • 2.0 Byr – BIFs, presence of oxygen in the atmosphere • 670 Myr – first evidence of multi-cellular life • 545 Myr – Precambrian-Cambrian boundary – Explosion of Life • 245 Myr – The Great Permian-Triassic Extinction (The largest extinction) • Myr – The KT (Cretaceous-Tertiary) Extinction (Dinosaurs) • 4 Myr – First hominids You do NOT need to know the details listed on paleomaps.

  26. Rock Deformation Read sections 8.1-8.5

  27. The Earth is a dynamic body (it moves over time) Forces that result from plate tectonic activity and other geological processes are commonly called “tectonic forces” Tectonic forces deform rocks mainly by faulting, folding, stretching, or shearing. folding faulting

  28. Whether a rock deforms by faulting, folding, shearing, or stretching depends on whether the rock is brittle or ductile. • When tectonic forces are applied to rocks: • Brittle rocks do NOT flow easily, so they break (faulting) • Ductile rocks flow more easily, so they fold, shear, or stretch. Note: Before, we stated that the lithosphere is strong and brittle. For the most part this is true, however, under some conditions, rocks in the lithosphere become ductile.

  29. Faulting and Folding occur over many length scales; in other words, faults and folds can be very large or extremely small.

  30. There are 3 main types of tectonic forces that act on rocks Compressive forces: forces that squeeze and shorten a rock Tensional forces: forces that stretch and pull apart a rock Shearing forces: forces that push two sides of a rock in opposite directions

  31. In ductile rocks Compressive forces causes folding Tensional forces causes stretching Shearing forces causes shearing compressive tensional shearing

  32. In brittle rocks Compressive forces causes reverse faulting and thrust faulting Tensional forces causes normal faulting Shearing forces causes strike-slip faulting compressive tensional shearing

  33. What controls whether a rock is brittle or ductile • Confining Pressure (remember, this is the type of pressure that increases with depth) • Near the surface where pressure is low, rocks are more brittle • Deeper in Earth where pressure is higher, rocks are more ductile • Temperature • At cooler temperatures, rocks are more brittle • At higher temperatures, rocks are more ductile • Type of rock • Some rocks are naturally more ductile than others • Examples to know: Shale and halite are usually very ductile compared to other rocks • Rate of deformation • Very slow rates of deformation (like plate tectonic motions) lead to more ductile behavior. • Fast rates of deformation (like what occurs during an earthquake) lead to more brittle behavior

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