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  1. DO NOW: Please get out your chapter 1 unit sheet and notes

  2. Unit 2: GeologyThe Earth

  3. History of the Earth

  4. History of Earth • Geologists believe the earth to be 4.6 billion years old. • This belief has been formed after dating layers of rock formations on the Earth.

  5. Three Major Types of Rock • Igneous Rock • Sedimentary Rock • Metamorphic Rock

  6. Igneous Rock • “From Fire” • Created when magma cools and hardens • Example: Rhyolite Note: magma is called lava if it cooks at the earth’s surface

  7. Sedimentary Rock • Sediment: rocks, minerals and organic material that have been broken into fragments from wind, waves, erosion etc. • When sediment deposits harden after being compressed, you have sedimentary rock • Example: Sandstone

  8. Metamorphic Rock • “changed form” • Existing rock can be changed by tremendous pressure, extreme heat or chemical processes • Example: Marble

  9. The Rock Cycle

  10. Age of the Earth How do geologists determine how old rocks are? • Relative dating -- determine whether the rock is older or younger than other rocks 2. Absolute dating -- use radiometric dating (carbon dating) techniques to determine how long ago the rock formed in the exact number of years *Not all rocks can be dated absolutely, so combinations of techniques are used.

  11. Relative Dating • The Law of Superposition: states that the rocks layers above are younger than the layers below

  12. Example of Relative Age Dating

  13. Absolute Dating Absolute Dating: • Use naturally-occurring radioactive isotopes to determine radioactive decay and half-life. • Isotope -- form of an element that has additional neutrons

  14. Rate of Radioactive Decay • Isotopes decay at a constant rate. • Rate of decay is measured by half-life • Half-life -- time it takes for one-half of the radioactive material to decay.

  15. Example: • A rock has 0.5 (one-half) of the original carbon 14 material in it. One can deduce that knowing the half-life of carbon 14 is 5730 years, the rock must have decayed (lost) 50% of its original carbon 14 material and is now 5730 years old. In a period of 5730 years from now, the rock will contain .25 (25%) of its original carbon 14 material. Theoretically, there will always be some trace of carbon 14 present in the rock…it will never decay totally.

  16. Why does this matter to us? • Scientists date the age of rocks and fossils by examining the amount of radioactive decay. • We have been able to determine the age of various rocks and fossils leading us closer to finding a more detailed history of our earth.

  17. Why does this matter to us? • In 2008 scientists dated the oldest rock currently know. The oldest rock is 4.28 billion years old.

  18. Why does this matter to us? • Although active geologic processes, such as plate tectonics and erosion, have destroyed or altered most of the very early rock record on Earth, some still exist and other objects in the solar system, such as lunar rocks, asteroids, and meteorites, have changed little over billions of years. • Studying these objects can provide information about Earth’s formation, early history, and a timeline for Earth’s creation.

  19. Why does this matter to us? • With the various forms of evidence (fossils, rocks, etc.) scientists have developed a geographic time scale to chart the history of our planet.

  20. Other theories about the history of our Earth More History…

  21. History of Earth’s Continents • Land masses have changed positions nearly continuously throughout the earth’s history. • According to the theory of continental drift, the earth’s surface is divided up into a dozen or so massive, rigid plates that rest on the earth’s more fluid mantle. These plates "float" on the mantle like oil floats on water.

  22. History of Earth’s Continents • Convection currents move the plates at roughly 2.5 centimeters per year • Convection Currents are caused by the very hot material at the deepest part of the mantle rising, then cooling, sinking again and then heating, rising and repeating the cycle over and over. These currents drive plate tectonics

  23. History of Continents • Alfred Wegner’s Theory of Continental Drift suggests that the supercontinent Pangaea began to break up about 225-200 million years ago, eventually fragmenting into the continents as we know them today.

  24. History of Continents • Plate tectonics (movement/ shifting of Earth’s plates) is the unifying theory that explains the past and current movements of the rocks at Earth’s surface and provides a framework for understanding its geologic history.

  25. Continental Drift • Evidence for the Theory of Continental Drift: • Remarkable fit of the continents • Large-scale geological features on separated continents match very closely when the continents were brought together (Ex: The Appalachian mountains of eastern North America matched with the Scottish Highlands) • Identical Fossil evidence: plant and animal fossils found on the matching coastlines of South America and Africa

  26. Additional Resources • • • Animation of Continental Drift •

  27. Earth Today

  28. You were each given a fact about Earth. Your goal is to discover all of the facts in a five minute period. FACTS ABOUT EARTH

  29. Fast facts about Earth • The Earth is spinning along an axis that goes from the North to South pole • It takes the Earth 23 hours and 57 minutes to make 1 full rotation on its axis. This is why we have 24 hours in a day. • A year on Earth It’s actually 365.25 days. It’s this extra .25 days that creates the need for leap years.

  30. More Facts • The deepest part of the ocean is almost 7 miles down, known as the Mariana Trench. • 90% of volcanoes occur under the ocean • The temperature of the Earth’s core is 9900 degrees Fahrenheit; as hot as the surface of the sun • The hottest recorded temperature on the surface of the Earth is 134 degrees Fahrenheit in California; The coldest recorded temperature on the surface of the Earth is -129.6 degrees Fahrenheit in Antarctica.

  31. More Facts • The Earth is 71% covered by water and 29% land. • Of all the water on Earth, 97% of water is salt water and 3% is fresh water. • Water on Earth is called the hydrosphere

  32. More Facts • There are 7 continents on Earth and they are constantly moving; this movement is known as continental drift.

  33. Structure of Earth Today

  34. Zones of the Earth

  35. Zones of the Earth • The Earth consists of three zones: • The Core • The Mantle • The Crust

  36. The Core • The core consists mostly of iron, with some nickel. The inner core is solid whereas the outer core is liquid (i.e., molten).

  37. The Mantle • The mantle is the largest zone; it is composed primarily of iron and magnesium. • The upper layer of the mantle is solid and rigid while the inner layer is partly molten and plastic.

  38. The Crust • The crust forms a thin skin over the earth’s surface. It has two parts: • Oceanic crust: plates under the sea floor, • Continental crust: plates under the continents

  39. 7 Continents on Earth’s Surface

  40. Oceans on Earth’s Surface

  41. MAPS

  42. Earth’s Hemispheres • The line that splits the Earth into two hemispheres is called the equator. • The lines that splits each hemisphere are called: • Tropic of Cancer • Tropic of Capricorn

  43. Latitude vs. Longitude • Latitude: circles that run east and west around the world parallel to the equator; called parallels • North of the equator are labeled N • South of the equator are labeled S

  44. Meridians • Split the Earth from North Pole to South Pole

  45. Latitude vs. Longitude • Longitude: circles that run from pole to pole; called meridians • West of the prime meridian are labeled W • East of the prime meridian are labeled E

  46. Latitude and Longitude