Reading rock layers and the history of life

Grade 6 Science Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Use this

   Two rock columns, not to scale.

3. 1.

   Two sites far apart both have a shale layer with the same index trilobite. Which layer at Site 2 matches the trilobite shale at Site 1, by Esme's matching?

   • The shale with the same trilobite
   • The conglomerate at the bottom
   • The coal on top, since it is the youngest layer there
   • Whichever layer is thickest
4. 2.

   At Site 1, limestone lies above the trilobite shale. At Site 2, coal lies above the same shale. What can Jun say about the limestone and the coal?

   Use the picture in question 1.

   • They must be exactly the same age
   • The coal is older than the shale
   • Both are older than the shale, since they are higher up
   • Both are younger than the trilobite shale
5. 3.

   Why is a short-lived, widespread fossil so useful for matching layers at sites far apart, as Kira explains?

   • It lived a long time, so it turns up in many layers
   • It shows which layer is on top at each of the two sites
   • Rocks holding it formed in the same short span
   • It shows the two sites were once touching
6. 4.

   A post says the thick rock layers in a canyon wall formed in just a few years. Milo checks it. Which response is best?

   • Disagree: the top layers are the oldest
   • Agree: thick layers like these can form in one rainy season
   • Disagree: the layers built up over millions of years
   • Agree: sand piles up meters each year in canyons like this
7. 5.

   Noah's cousin says any fossil can tell the exact age of a rock. Which response is best?

   • Agree: bigger fossils are older, so their size tells the age
   • Disagree: fossils show nothing about age
   • Disagree: index fossils narrow the age; radioactive dating gives numbers
   • Agree: each fossil shows its own year
8. 6.

   Cross-section, not to scale. Layers A (bottom), B and C are cut by a dike. Layer D lies on top and is not cut. Which order of events, oldest first, does Pia choose?

   • Layers A, B, C, D, then the dike
   • Layers A, B, C, then the dike, then D
   • Layer D, then C, B, A, then the dike
   • The dike first, then layers A, B and C, then layer D
9. 7.

   A fault cuts layers A to C. Layer B holds an index fossil from about 300 million years ago. What can Ren say about the fault?

   • It is older than 300 million years, since it cuts deep
   • It is younger than about 300 million years
   • It formed this century
   • It is exactly 300 million years old
10. 8.

    The bottom layer has ichthyosaurs (sea reptiles) and ammonites, the middle layer has ammonites but no ichthyosaurs, and the top layer has neither. Which story fits, by Tala's reading?

    • The three layers formed in one year
    • Both groups still live in those seas
    • Ichthyosaurs became extinct first; ammonites lasted longer
    • Ammonites became extinct first; ichthyosaurs lasted much longer

11. A 24-hour clock face for Earth's history

    Midnight at the start is Earth forming; the next midnight is today.

12. 9.

    Squeeze Earth's 4.5 billion years into one 24-hour day. When does Zee find that dinosaurs (other than birds) became extinct?

    • At about 11:39 p.m.
    • At about 6 p.m.
    • At about noon
    • Seconds before midnight, alongside the first people
13. 10.

    On the same 24-hour day, when do modern people appear, about 300,000 years ago? Ari works it out.

    • In the very first hour, just as the Earth formed
    • At about noon, halfway through
    • About 6 seconds before midnight
    • At about 11:39 p.m., with the dinosaurs