Chapter 28.1 modern geology
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  • 1. Chapter 28.1Understanding Earth CPO Science Neistadt
  • 2. Integrated Science Unit 10, Chapter 28
  • 3. 28.1 Understanding Earth *Geologyis the study of rocks and materials that make up Earth and the processes that shape it. In1666, Nicholas Steno (1638-87) noticed that shark’s teeth resembled mysterious stones called “tonguestones” that were found in local rocks.
  • 4. 28.1 Understanding Earth Steno’sexplanation helped him develop ideas about how rocks and fossils form. These ideas are used in a technique called relative dating. *Relative dating is a way to put events in the order in What happened here and in what order? which they happened.
  • 5. 28.1 Understanding Earth *The approximate age of each layer of a rock formation can be determined by applying Steno’s idea called superposition.  A stack of newspapers illustrates superposition.  *Superposition means that the bottom layers of rock are older than the layers on the top.
  • 6. 28.1 Understanding Earth *Original horizontality states that sediment particles fall to the bottom of a basin, such as a riverbed, in response to gravity and result in horizontal layers.
  • 7. 28.1 Understanding Earth *Lateral continuity is the idea that layers of sediment extend in all directions when they form and before they become rock layers. The idea of lateral continuity states that layers of rock are continuous unless a geologic event like a river interrupts the layers or an earthquake them.
  • 8. Superposition Lateral Continuity OriginalHorizontality
  • 9. 28.1 Understanding Earth Anotherimportant idea, developed by Scottish geologist James Hutton (1726-97), is that the "present explains the past." *The idea of cross- cutting relationships states that a vein of vein rock is younger than the rock that surrounds a vein.
  • 10. 28.1 Understanding Earth Sometimes rock pieces called inclusions are contained in another rock. *During the formation of a rock with inclusions, sediments or melted rock surrounded the inclusion and then solidified. *Therefore, the inclusions are older than the surrounding rock.
  • 11. 28.1 Understanding Earth *Over geologic history, many animals and plants have lived and become extinct. *Their remains have become fossils. *The idea of faunal succession states that fossils can be used to identify the relative age of layers of a rock formation.
  • 12. 28.1 Calculating Earths Age  William Thompson Kelvin (1824-1907), known for proposing the absolute temperature scale that came to be named after him, meticulously calculated Earth’s age to be between 10 million and 100 million years.  Lord Kelvin’s calculation was not accurate because he did not realize that Earth has internal heat from the core and radioactive decay.
  • 13. 28.1 Calculating Earths Age  Earth’s age was estimated by measuring the radioactive decay of uranium to lead.  With improved techniques and evidence from tree rings and glaciers:  *The age of Earth is estimated to be about 4.6 billion years.
  • 14. 28.1 The Layers of the Earth Earth’s surface is covered with a thin crust. There are two kinds of crust: — continental — oceanic
  • 15. 28.1 Convection inside Earth  The rocky material of the mantle moves in very slow convection currents.  This movement is related to density and temperature differences in the mantle.  Hot material is less dense and rises.  Cold material is denser and sinks.
  • 16. Structure of the Earth:
  • 17. 28.1 Understanding EarthKey Question: What story is hidden here?*Read text section 28.1 BEFOREInvestigation 28.1