SDS Episode1 - The Formation of Sedimentary Rocks

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How do sedimentary rocks form?

Let's travel through the canyon country of Utah and Arizona to find out.

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SDS Episode1 - The Formation of Sedimentary Rocks

  1. 1. Get Your High School Diploma Online<br />Science Discovery Series<br />Olympus High School<br />Jeff Taylor<br />Science Instructor<br />
  2. 2. Episode 1Sand Dunes and Sedimentary Rocks<br />Paria Canyon, AZ<br />How They Form<br />
  3. 3. Grand Staircase-Escalante NM, UT<br />Sandstone<br />Sandstone are layers of sand-sized particles that are cemented together.<br />The cement determines the strength of the sandstone.<br />Sandstone can form from sand dunes, river or lake bottoms, or former beaches.<br />
  4. 4. Great Sand Dunes NP, CO<br />Sand Dunes<br />Sand Dunes form where sand particles are blown in the wind and then pile up in a place where the wind slows.<br />Rain trickles down to the bottom of the dunes.<br />Minerals that dissolve in water cement the sand and solidifies the base.<br />
  5. 5. Lithification<br />Maui, HI<br />These sand dunes have lithified when water seeped in and cemented the sand grains.<br />Later, winds blew away the loose sand above.<br />
  6. 6. Navajo Sandstone, Big Water, UT<br />Sandstone<br />Fossilized sand dunes can be determined by their cross-bedding.<br />Cross-bedding are alternating layers that are tilted against each other.<br />
  7. 7. The Dive, Grand Staircase-Escalante, UT<br />Navajo Sandstone<br />They formed in an ancient Sahara-like Desert some 75 million years ago<br />
  8. 8. PlayasEvaporite Basins<br />Carrizo Plain NM, CA<br />Salts dissolve from rocks into rainwater<br />Water gathers at the valley floor to form shallow lakes<br />Hot summer evaporate the water, leaving just a flat salt layer<br />This salt can be sodium chloride or a variety of alkaline substances like gypsum, calcite, or soda.<br />
  9. 9. Gypsum Dunes<br />White Sands NM, NM<br />When evaporites from a dry lake are broken into small pieces and blown in the wind, they can pile up into dunes.<br />At White Sands, NM the “sand” will dissolve in your mouth!<br />
  10. 10. Vermillion Cliffs Wilderness, UT<br />Lake or Ocean Sandstones<br />Sandstone layers that are completely horizontal are usually formed at the bottom of lakes or the ocean.<br />
  11. 11. Lake and Ocean Settling<br />When sediment flowing down a river meet a lake, they drop out and settle to the bottom to form a flat layer.<br />
  12. 12. Lake Sediments<br />Here, changing lake levels leave horizontal beds of sediments.<br />When buried, they will compact into stone.<br />
  13. 13. River Deposited Sandstones<br />
  14. 14. Ripple Marks<br />Ripple marks are a sign on an ancient stream or lake shore<br />
  15. 15. Conglomerates<br />Conglomerates are a mixture of rock sizes that form in rivers.<br />Large rocks are cemented together with sand, mud, and salts.<br />
  16. 16. Conglomerates forming today<br />This stream bed is making a conglomerate layer for future aliens to discover<br />
  17. 17. Mudcracks and Silt Layers<br />
  18. 18. Red Sandstones<br />Stained by iron oxide (rust) minerals<br />
  19. 19. Soft Sandstones<br />Some sandstones are so weakly cemented, that they “melt” when it rains and fall apart in your hands.<br />
  20. 20. Blue Sandstones Stained by Copper<br />
  21. 21. Various Minerals in the Rock<br />
  22. 22. Siltstones<br />Siltstones are similar to sandstone, but the grains are much finer.<br />They form at the bottom of the ocean and lakes where very small particles settle to the bottom.<br />
  23. 23. Clays and Mudstones<br />In the ocean or lake bottoms where microscopic particles settle, mud and clays cement together for form layered rock.<br />Mudstones are strong and well cemented.<br />Clays tend to be weaker and easily crumble.<br />
  24. 24. HoodoosConglomerate Capping Sandstone<br />Hoodoo’s form where strong rock protects weaker rock underneath<br />
  25. 25. Volcanic Ash<br />Volcanic ash can settle onto the ground or into lakes to form sediments.<br />
  26. 26. Bentonite Clays<br />Bentonite clays form when volcanic ash from eruptions lands in water.<br />This ash mixes with the mud and organic matter for form a weak, puffy layer, that is extremely sticky when wet.<br />
  27. 27. More Bentonite Clay<br />
  28. 28. Evaporites<br />When lakes or shallow ocean areas evaporate, they leave their salts behind. <br />These salts form layers of crystals.<br />
  29. 29. Tufa<br />When springs in a soda lake emerge, they deposit their minerals in large pillars.<br />
  30. 30. Evaporite Basin<br />Water drains down into the basin.<br />The water evaporates, leaving salts behind<br />
  31. 31. Coal, Oil, and Natural Gas<br />When organic matter such as dead plants get buried in mud it can be preserved as layers of coal.<br />Oil and Natural gas pockets can also form under these layers, typically with the help of heat underground.<br />
  32. 32. Petrified Wood and Fossils<br />Hard organic remains such as tree trunks, bones, and teeth can be fossilized as their natural minerals get replaced by other minerals.<br />
  33. 33. Fossils<br />The calcium and carbon of Petrified wood and fossil bones are often replaced by quartz or magnesium.<br />
  34. 34. Limestone<br />When the shells of clams, snails, or coral reefs are preserved in the ocean sediments, limestone forms.<br />Limestone is made of Calcium Carbonate.<br />Limestone is a sure sign that an area was tropical once.<br />
  35. 35. Travertine<br />Limestone dissolves in water.<br />Where water trickles down into the layers, it eats away at the rock forming caves and sinkholes.<br />When the water drips in the caves and evaporates, it leaves the limestone behind again forming Stalactites.<br />
  36. 36. Limestone Continued…<br />Since limestone dissolves in water, it forms steep and interesting landscapes due to erosion.<br />
  37. 37. More Limestone features<br />
  38. 38. More Limestone Features<br />
  39. 39. Limestone<br />Since Limestone is weak, it was often carved into for ancient tombs<br />
  40. 40. Glacial Till<br />Glaciers carve and pulverize rock into silt.<br />This silt is transported by ice and melt water to the edge of the glacier.<br />Here it forms layers that are easily broken.<br />
  41. 41. Erosion<br />Rivers and rain carve deep canyons into sedimentary rock.<br />
  42. 42. Zion Canyon<br />2000 feet deep sand dunes cut by the river<br />
  43. 43. Sandstone Canyons<br />
  44. 44. Grand Canyon<br />5000 ft deep with alternating layers of limestone, sandstone, siltstones, and fossils going back over 1 billion years.<br />
  45. 45. Slot Canyons<br />Occasional torrents of water from flash floods can carve deep narrow canyons into sandstone.<br />Some storms will flood this canyon with water 80 feet high!<br />
  46. 46. From Rock to Rock<br />Rivers deposit the sand from erosion in new locations to become new sandstone layers for future Geologists!<br />
  47. 47. Erosion<br />Rain, Ice, and Wind can combine to form some strange erosional features!<br />
  48. 48. Arches<br />Wind erosion is primarily responsible for natural arches. <br />Ice and rain also play a role in weakening lower layers of rock.<br />
  49. 49. Quiz – How did this form?<br />Devil’s Golf Course<br />
  50. 50. Tilting<br />Plate movements can cause the layers be be thrust upwards, downwards, or twisted.<br />

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