1 / 23

The Rock and Fossil Record

The Rock and Fossil Record. Chapter 6. Relative Dating. What is it? Figuring out whether an object or event is older or younger than other objects or events is called relative dating. Comparing the age of a rock to the rocks around it.

alair
Télécharger la présentation

The Rock and Fossil Record

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. The Rock and Fossil Record Chapter 6

  2. Relative Dating • What is it? • Figuring out whether an object or event is older or younger than other objects or events is called relative dating. • Comparing the age of a rock to the rocks around it. • In other words, you are estimating the age of a rock in relation to other rocks.

  3. The Principle of Superposition • Younger rocks on top and Older rocks on bottom!

  4. It is not just that easy…. • Not all rock sequences are arranges with the oldest layers on the bottom and the youngest layers on the top… • There are disturbances! • The forces with in Earth can push other rocks into sequences • Tilt or fold rock layers! • Break sequences into parts that move! • Some sequences are even upside down! • There is a valuable tool to help us with this confusion…

  5. … The Geologic Column! • What is it? • An arrangement of rock layers in which the oldest rocks are at the bottom • Geologists rely on the geologic column to interpret the order of rocks So, is there a place on Earth that has a continuous sequence of all the rocks formed throughout history?

  6. NO!

  7. NO… ??? • There is no single location on Earth that has a continuous sequence of all the rocks in order • Scientists have put different rock layers in order to form the Geologic Column to determine the relative age of rocks and other objects!

  8. Let’s Talk about the Disturbances! • Read P. 158 – 159

  9. Missing Evidence • Missing rock layers create breaks in rock-layer sequences = unconformities! • Unconformity is a break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time • In other words, a rock layer that is partially missing due to erosion and is always younger than the rock layers beneath it! You just look for what is missing!

  10. Try this one!

  11.  Did you get it?  12 11 10 9 8 5 4 7 3 6 2 1

  12. Absolute dating • The process of establishing the age of an object by determining the number of years it has existed is called absolute dating • You can figure out the absolute age of a rock if you know the rate of decay for one of the elements in the rock • Determining that age is called radiometric dating • A half-life is the time it takes one-half of a radioactive sample to decay

  13. Petrified Remains • Hard and rock like • Original material replaced by minerals • Ex. bones, wood

  14. Carbonaceous Films • Burial forces gases and liquid out • Forms thin film of carbon residue • Outline of organism • Ex. plants

  15. Mold & Cast • Organism is buried • Outside decays leaves a cavity = mold • Sediment fills in mold and hardens to rock = cast The cast looks like the organism!

  16. Original Remains • actual or part of organism • trapped in Amber – insects • frozen – woolly mammoth • tar pits

  17. Los Angeles La Brea Tar Pits This is a recreation of a tar pit that illustrates how animals would get trapped in tar pits. • What is a tar pit???

  18. Trace Fossils • evidence of animal activity • tells how organism lives • Ex. tracks, worm holes Worm tracks! ↓ These are dinosaur foot prints!!

  19. ScienceDo Now: 10-20 HW: COMPLETE THE FOSSIL RECORD ACTIVITY W/QUESTIONS ON THE BACK 1.Clear your table TODAY ~ Fossil Record activity ~ candy update

  20. Index Fossils • Used to date other fossils and rock layers. • Fossils of animals that • Existed for a short period of time • Were abundant, there were many of them • Lived all over the world EUOMPHALUS But wait…. There’s more…. TRILOBITE

More Related