1 / 69

Interpreting Geological History

Interpreting Geological History. Aim GeoHis 1a - How old is Mr. Foley relative to the planet Earth?. Reading the Rock Record. Human recorded history only 10,000 years of recorded human history Since the Agricultural Revolution 8,000 BCE Geologic history 4.6 billion years old

faithv
Download Presentation

Interpreting Geological History

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Interpreting Geological History Aim GeoHis 1a - How old is Mr. Foley relative to the planet Earth?

  2. Reading the Rock Record • Human recorded history • only 10,000 years of recorded human history • Since the Agricultural Revolution 8,000 BCE • Geologic history • 4.6 billion years old • Cosmological History • Our universe is 13.8 billion years old

  3. Relative Dating • This is not talking about how old your Aunt Matilda’s is! • Relative dating - the age of one object, rock, fossil, event compared to another • Example: Who is oldest: • Mr. Foley? • The Earth? • Mr. Foley’s daughter Katie?

  4. Another Example of Relative Dating – place the following in number order • Japanese Attack on Pearl Harbor • Abraham Lincoln’s Gettysburg Address • Atomic bombing of Hiroshima • The September 11 attacks • Columbus discovers America • First men land on the Moon • John F. Kennedy is assassinated • Signing of the Declaration of Independence • The Titanic sinks after hitting an iceberg

  5. An Example of Relative Dating 5. Columbus discovers America 8. Signing of the Declaration of Independence 2. Abraham Lincoln’s Gettysburg Address 9. The Titanic sinks after hitting an iceberg 1. Japanese Attack on Pearl Harbor 3. Atomic bombing of Hiroshima • John F. Kennedy is assassinated 6. First men land on the Moon 4. The September 11 attacks

  6. Absolute Time • Identifies the actual date of an event • Example - the date that Pearl Harbor was bombed would be absolute • If two dates are known for two events • than the length of time between the events will be known • We can calculate rates of change • how long a mountain took to build up • how many years it took for a glacier to advance

  7. Absolute Dating with Radioactive Elements • The Earth, from its origin, has had radioactive elements within it • Radioactivity – the breakdown of unstable atoms due to too many or too few neutrons in the nucleus • Energy is released when radioactive elements breakdown or decay • This heats the Earth’s interior

  8. Absolute Dating with Radioactive Elements – three types of decay • There are three types of decay • Alpha decay - a helium particle is emitted • Beta decay - a high energy electron is emitted • Gamma decay – a high energy electromagnetic wave is released • Half Life • A time period equal to how long it takes half of a radioactive sample to decay

  9. Typical Half Life graph

  10. Correlation – How layers of rock relate to each other • Allows us to SEQUENCE events • Shows relative as well as absolute dating • Allows us to FIND • Useful minerals • Fossil fuels like coal and oil • Correlation is done by • Studying exposed bedrock (outcrops) • Looking for similarities between two different places • Following the Laws of Rock Sequencing

  11. 1st Law - Law of Superposition • If sedimentary rock layers are undisturbed • Lowest layers of sedimentary rock will be the oldest

  12. 2nd Law - Law of Cross-Cutting Relationships • If an intrusion of igneous rock cuts across existing sedimentary rock • It is younger than the sedimentary rock

  13. 3rd Law - Law of Included Fragments • Pieces of rock found in another rock must be older than the rock they were found in • Each mineral is older than the rock it makes up! • Example • A conglomerate rock • Contains granite, limestone, and clay • Rock is younger than the three materials in the rock

  14. 4th Law - Law of Unconformity • A place where rock layers are missing • Either rock layers are lost due to erosion or may not have been laid down at all • Creates gaps in the rock record (“Darwin’s Bane”) Unconformities are erosional features… might we lose a fossil or two?

  15. Correlations Continued Aim GeoHis 2 - How do I use the Laws of Geology to figure out the age of rock layers or strata?

  16. Some examples of Correlations • In the following diagram at the right • Give the order of the layers produced • From oldest to youngest • M • L • Lava Flow A • Magma Chamber N • K, J, H, G, F • Intrusion I • Sill E • D • Lava Flow B • C C D E F G H I J K L M N

  17. Some examples of Correlations • In the following diagram at the right • Give the order of the layers produced • From oldest to youngest • A • B • C • D • Fault line G • Unconformity • E • F • Intrusion H • Contact Metamorphism of F F E D C B A Intrusion H Fault line G

  18. Some examples of Correlations • In the following diagram at the right • Give the order of the layers produced • From oldest to youngest • A • B • C • D • Fault line G • Unconformity • E • F • Intrusion H • Contact Metamorphism of E and F F E D C B A Fault line G

  19. Mountains and Plate Tectonics Revisited Active and Passive Continental Margins - the edges of continents 1. Active margins • occur along the edge of a plate boundary • produce earthquakes and volcanic activity • mountain building results • Ex: Andes Mtns of South America (“Alive”)

  20. What Characteristics Occur in Collision Mountains Faults – where plates meet Types of faults • strike-slip faults • shear forces - sideways • normal faults • tensional forces – pull apart • thrust faults • compression forces – push together • all build up mountains by pushing crustal materials up into piles

  21. What Characteristics Occur in Collision Mountains Folds – when plates collide – sometimes earth folds up • Anticlines • upfolds of rock • Synclines • downfolds of rock • A fjord in Norway

  22. Other Evidence of Mountain Building Uplifting – proof of increasing elevations: • fossils • marine animals found at higher elevation • raised beaches • example California • Shows measured changes in elevation along coastlines Holy Schist! That’s a big fossil clam!

  23. Other Evidence of Mountain Building Tilting • areas where large amounts of sedimentary rock are tilted due to movement of the crust • Ex: Rocky Mtns in Colorado sedimentary rocks Fault block mountains • Areas where numerous fault lines occur • May create a series of raised mountain segments Horst – the raised part of the fault block Graben – the lowered part of the fault block

  24. Sed Rock Layer 1 myo Sed Rock Layer 5 myo Sed Rock Layer 2 myo Sed Rock Layer 4 myo Sed Rock Layer 3 myo Sed Rock Layer 3 myo Sed Rock Layer 2 myo Sed Rock Layer 4 myo Sed Rock Layer 5 myo Sed Rock Layer 1 myo Other Evidence of Mountain Building Overturning • When sedimentary layers are flipped over • Can occur due to excessive tilting • What is the Law of Superposition and how does this break that law? • Oldest rocks on bottom, youngest on top • In overturning, its reversed!

  25. Fossils and the Age of Rock Aim GeoHis 3c – How do fossils help us date rock strata?

  26. The Fossil Record • Fossils – any evidence of earlier life preserved in a rock • Found only in sedimentary rock… • Why???

  27. Fossils - Original Remains • Parts of the actual animal or plant • Preserved in ice, tree sap, or peat (from bogs) • Examples • Wooly Mammoths – frozen in ice • Insects, seeds, plant parts – stuck in amber (tree sap will harden) • The Bog People – buried in a bog (swamp)

  28. Examples of Original Remains

  29. Dinosaur bones • The calcium in the bones is replaced by other minerals • Over time, the bones last longer • An example of Archaeopteryx an ancient ancestor to modern birds

  30. Fossils - Replaced Remains • Soft parts lost thru decay • Hard parts replaced by other minerals such as: • Calcite • Silica • Pyrite • Hardens to form a mineral-like substance • Examples – petrified wood!

  31. Examples of petrified wood

  32. Fossils - Molds and Casts • A plant or animal falls into some sediments (ex: mud or clay) • Plant or animal decays, but leaves outline in sediment (a mold) • Sediments then form sedimentary rock • If other materials fill in the mold • A cast is formed

  33. Examples of Molds and Casts

  34. Shells Molds

  35. Trace Fossils • Evidence of life other than actual remains • Examples: • Footprints • Tracks • Trails • Burrows • Borings • Coprolites…

  36. Foot prints

  37. Tracks • What happened here??? • Someone was having dinner, and someone WAS dinner!

  38. Coprolites • What is it? • Oh no! Dino Poo!!! • Tells us about the things they ate…

  39. Index Fossils and Key Beds • Index fossils • Excellent for RELATIVE dating • Fossils with three special characteristics: • Easily recognized • Widespread throughout the world or a region • Occurred in very specific time periods

  40. Index Fossils and Key Beds • Key Beds – rock layers that have the same characteristics as an index fossil • This can be done across the face of the Earth • Best example – iridium layer at 65 mya (who died?)

  41. Geologic Timetable • Geologic timetable – see ESRTs pp. 8-9 • A summary of the major events in geologic history – includes: • Time scales • What life was on earth during those time scales • The NYS rock record – what time scales we have evidence of • What animals and plants were found in NYS and what time periods their fossils came from • Major North American and NY tectonic events • The position of North American relative to Pangea

  42. Geologic Timetable • Era - the longest segment of geologic time • Each era broken into periods • Each period broken into epochs • Archean Era • Began 4.6 billion years • Oldest rocks come from this time range • Proterozoic Era • Began 2.5 billion years ago • First fossils of simple plants and worms found here (oceans only)

  43. Geologic Timetable Paleozoic Era • Began 570 million years ago • Abundant fossil record • Land and ocean animals and plants

  44. The Paleozoic – Life takes on a whole new meaning

  45. Geologic Timetable Mesozoic Era • Began 250 million years ago • Rise and Fall of the Dinosaurs • Earliest birds and mammals • Rise of flowering plants over conifers

  46. Mesozoic Era – Rise of the Dinosaurs

  47. What really killed off the dinosaurs…

  48. Geologic Timetable Cenozoic Era • Began 65 million years ago • Rise of the birds and mammals • Ice ages • Mammoths and Saber tooth tigers • Human Epochs • Australopithecus afarensis – “Lucy” of Olduvi Gorge • Homo habilis – “handy man” • Homo neanderthalsis – the “caveman” • Homo sapiens – “thinking man” • Homo sapiens sapiens – modern man

  49. Cenozoic Era

  50. Half Life Calculations Aim Geo His 5e – How does radioactivity allow us to date the dinosaurs?

More Related