Earth history 1
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The document provides an overview of Earth's geological history and processes. It discusses how heat from the Earth's core and energy from the sun drive plate tectonics and geological changes over long periods of time. Precise dating methods like radiometric dating indicate that the Earth is approximately 4.5 billion years old, much older than traditionally thought. The constant recycling of the crust through igneous, sedimentary, and metamorphic rock processes comprises the long-term geological evolution of our planet.
Earth history 1
- 1. EARTH HISTORY 1: Geological Changes ppt. by Robin D. Seamon HOOK VIDEO: Ian Stewart: Volcanoes (50 min)
- 2. • Earth is dynamic (changing) • Heat from the center • Energy from the Sun INSIDE: • Decay of radioactive isotopes • The release of this heat causes: • churning of the molten rock inside • Release of heat through cracks/vents in the crust • Convection causes plates of crust to move about
- 3. OUTSIDE: • Sun’s Energy on the atmosphere and water make: • Wind • Currents • Evaporation- Water Cycle • This causes weather & larger patterns of climate • It influences Water Cycle which controls weathering, erosion, & deposition http://www2.mps.mpg.de/projects/sun-climate/se_body.html
- 4. INSIDE • 99% of rock inside the Earth is greater than 2,000˚F (radioactive decay generates the heat) • Crust: (0.2 – 1.1 % crust or 4-43 miles deep) 700˚F- 1,500˚F • Mantle: (45 % interior) hot magma 7,000˚F • Core: (54% of interior) Fe, Ni 10,000˚F
- 5. COMPOSITION: • Scientists study earthquake waves to determine what’s inside • Pattern of waves through the Earth shows something dense in the center • Fe (iron) fits this description & also explains magnetic field http://www.indiana.edu/~geol105/images/gaia _chapter_3/seismic.htm
- 7. • Geothermal: relating to heat inside the earth DEEPEST man-made hole: • Kola Superdeep borehole- NW Russia • 40,000 ft & then too hot to dig more Crust 21 miles deep in Baltic Region At 7.4 miles, 300˚F Average oil well is ~ 1 mile Scientists try to harness this geothermal Energy for renewable Energy source
- 8. OUTSIDE • Plate Tectonics: plates move about ½” to 3” a year • Theory that the Earth’s lithosphere is composed of 10+ plates that fit together like a puzzle http://www.bucknell.edu/x17758.xml
- 11. • The plates move slowly on the upper mantle (asthenosphere) http://kids.britannica.com/comptons/art-156130/A-diagram-shows-the-relationship- between-volcanic-activity-and-Earths VIDEO: Plate Tectonics (1.5 min)
- 12. • Movement is caused by convection inside the Earth • Hot goes up, cold goes down- • plates are along for the ride • Continental Drift: in the 1900’s scientists realized the plates were moving, but didn’t know why (Alfred Wegner) 1. *VIDEO: The Early Earth & plate tectonics-National Geo (5min) 2. VIDEO: Plate Tectonics: A documentary (7 min)
- 13. FAULTS LAB
- 14. Spain FAULTS LAB
- 15. Landforms & Forces that Made Them Constructive or Destructive? Constructive force: forces that build up new crust Destructive Forces: forces that destroy crust Sporadic or Gradual? Sporadic event: event happened quickly and suddenly Gradual event: event happened over a long period of time
- 16. • Volcanoes: sometimes the heat can escape through vents at the surface; magma & hot gases from inside are released until pressure is abated • Largest- Mauna Loa, Hawaii 18,000square miles • Big eruptions occur several times/Century • Shield volcano: layers of lava released from non-explosive eruptions (Mauna Kea, Hawaii)
- 17. • Cinder cone volcano: pyroclastic material- dust & ash explodes out (Paracutin, Mexico) Composite volcano: pyroclastic explosions followed by slower, longer flowing-lava (Mt. St. Helens
- 18. • Earthquakes: tension builds up at plate boundaries until the plates slip & tension is released- we feel earthquakes Tsunami: when earthquake happens under the ocean
- 19. EVIDENCE in CRUST • Uplift: places on the crust that bulge upwards because of pressure underneath • can help predict future earthquakes or eruptions http://www.panoramio.com/photo/15735758 http://bc.outcrop.org/GEOL_B10/lecture18.html
- 20. • Predicts tension at a divergent boundary • Predicts loss of material below • Subsidence: places on the crust that are sinking down in elevation
- 21. • Rebound: places on the crust that rise in elevation when a heavy weight is removed • Ice sheet melts • During droughts when water table is emptied • Heavy building is removed http://bprc.osu.edu/education/rr/webex/WebExGridLinks2Pg6.html
- 22. FAULTS & BOUNDARIES • Compression: two plates are pushed together at convergent boundaries Results in: • Subduction (cooler oceanic crust goes beneath warmer continental crust) • Folding (crust folds into mountains) • Faulting (crust pushes up or falls in block mountains) • Hanging wall • Footwall • earthquakes ADVANCE
- 23. Folded Mountains http://freddoty.com/folded-mountains near the Sullivan River in the Canadian Rockies The Cape Fold Belt Mountains http://www.geocaching.com/geocache/GC2CEJP_steytlerville-arch?guid=ff36205a-b979-422c-8266-f7f83ec4d884 BACK
- 25. BACK
- 27. • Tension : two plates are pulled apart at divergent boundaries Results in: • Sea-floor spreading (new sea floor is made) • Trenches or rifts (gashes made from the pulling apart) • Subsidence or faulting • earthquakes Thingvellir Breach, Iceland VIDEO: Sea Floor Spreading- Nye (3 min)
- 28. • Shear : two plates slide past each other horizontally in a transform boundary Results in: • Ridges • earthquakes San Andreas Fault, Ca
- 29. ROCK CYCLE • Rock Cycle: process by which new crust is continually being recycled At plate boundaries: -pull apart (making new crust) -push together (forming mountains) -subduct (under other plates) http://www.perfecthomepictures.com/277773-gabbro-igneous-intrusive-phaneritic
- 30. PROCESSES: 1. crystallization 2. heat & pressure 3. weathering/erosion/deposition 4. Compaction/cementation 5. Melting -VIDEO: Rock types & Rock Cycle (4min) -ACTIVITY LINK http://www.passmyexams.co.uk/GCSE/physics/rock-cycle.html
- 31. • Igneous rock: rock formed from cooling magma • Intrusive igneous: crystalizes inside the earth slowly (hot in there) making larger crystals • Extrusive igneous: crystalizes fast outside the earth (cooler) making fewer crystals INTRUSIVE EXTRUSIVE granite gabbro basalt obsidian
- 33. • Metamorphic rock: rock is under heat & pressure for a long time so that it chemically changes into another type of rock granite gneiss sandstone quartzite slate schist coal diamond
- 35. • Sedimentary rock: rock is formed over time by sediments being compacted together • Hold fossils that describe Earth’s early life forms • The strata (layers) help determine relative age of rock Clay sediment makes shale Sand sediment makes sandstone Mineral deposits in water make limestone Dead plants & animals make fossil fuels Gravel, shell, & fossils make conglomerate
- 37. HOW OLD IS THE EARTH? • Age of the Earth has been debated for Centuries TRADITIONAL VIEW: • At first scientists thought that the Earth was formed & has been cooling ever since (not true)… led to wrong numbers • They thought the earth was static & that only catastrophes led to changes • We now know earth has a heating mechanism inside causing changes in the shape of the crust!
- 38. Despite these incorrect numbers, geologists had some correct ideas too: • Nicolas Steno 1660’s studied sedimentary rocks Relative Dating • Law of Superposition: said that sediment layers (strata) are deposited in a time sequence: oldest on bottom, youngest on top http://www.angelfire.com/az3/mohgameil/physical.html
- 39. • Unconformity places where no sediments were preserved (erosion) for a time; separates different ages Angular unconformity
- 41. • Principle of original horizontality: said that layers of sediment are originally deposited horizontally • (therefore if they aren’t, something moved them after they were laid down) • Principle of cross-cutting relationships: says that a feature is younger than the feature it cuts across
- 42. • William Smith 1790’s • Hypothesized that if two layers of rock at different locations contain similar fossils, then rocks must be the same age • Index fossils: fossils used to determine relative age of rocks
- 43. NEW CONTROVERSIAL IDEAS: 1800’s • Charles Lyell 1830 • geologist who said the Earth’s features were constantly changing & therefore Earth was much older than previously thought • (PEOPLE DID NOT LIKE IT) • Uniformitarians: changes were constant and uniform: processes at work in the past are still occurring today
- 45. MODERN DATING METHODS 1900 Radioactivity discovered (unstable atoms) Absolute Dating • Radiometric dating using radioactive forms of elements in rock to determine the age of the rock or fossil
- 46. How it works: • Atoms in an element have the SAME number of protons • Sometimes their number of neutrons is different: isotopes • Radioactive: unstable isotopes break down (decay) over time • Decay happens at steady rate for each element • Half-life: time it takes for ½ of the sample to decay (scientists know for each element) • Compare amount of parent isotope to daughter isotope to know age of rock/fossil Amount Parent isotope Amount Daughter isotope AGE OF ROCK/FOSSIL
- 47. 50 % 25 % 25 % 25 % 50 % 100 % 50 % PERCENTAGES 1/2 25 % 1/4 1/4 1/2 1 whole 1/2 FRACTIONS RADIOACIVE DECAY
- 48. Common types: Potassium-Argon (> 1000,000 ya) Uranium-Lead (> 10 million ya) Rubidium-Stronium (>10 million ya) Carbon-14 (in fossils) VIDEO: Radiometric Dating (5 min)
- 49. VIDEO 3: Radiometric dating Geologic Time 5 min
- 50. Magnetic reversals: evidence is left in the seafloor along divergent boundaries that the Earth’s poles have reversed randomly many times in Earth’s past • New igneous rock, if it has metal in it will magnetize • There are places in the seafloor’s ‘record’ that are opposite to Earth’s current field • This pattern is also seen in seafloor core samples • Important means of dating for metamorphic & igneous rock samples (no fossils)
- 51. • If rock becomes molten, radioactivity escapes & we can’t determine age • Rock Cycle??? • How old is the Earth? • We use- • Samples from Earth (oldest Zircon crystal found so far in Australia) • Samples from meteorites that hit Earth • Samples from the moon • Date the Sun based upon luminosity & Energy as compared to other stars • Ice core data…
- 52. … So most scientists agree that with current technology, the Earth is… 4.5 billion years old VIDEO: COSOMOS- The Clean Room (45 min) VIDEO 1: Big Idea Age of the Earth 5 min VIDEO 2: History of Earth in 5 ½ minutes 5.5 min VIDEO 3: World’s Most Asked Questions-How old is the Earth? (2:50)