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

   • The coal is older than the shale
   • Both are younger than the trilobite shale
   • They must be exactly the same age
   • Both are older than the shale, since they are higher up
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
   • Rocks holding it formed in the same short span
   • It shows the two sites were once touching
   • It shows which layer is on top at each of the two sites
6. 4.

   Luz's friend says early people and dinosaurs lived at the same time. Which response is best?

   • Disagree: those dinosaurs were extinct about 66 million years before people
   • Agree: cartoons and movies often show them living together
   • Disagree: dinosaurs lived after people
   • Agree: their fossils are in the same layers
7. 5.

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

   • Agree: sand piles up meters each year in canyons like this
   • Disagree: the layers built up over millions of years
   • Agree: thick layers like these can form in one rainy season
   • Disagree: the top layers are the oldest
8. 6.

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

   • Disagree: index fossils narrow the age; radioactive dating gives numbers
   • Agree: bigger fossils are older, so their size tells the age
   • Agree: each fossil shows its own year
   • Disagree: fossils show nothing about age
9. 7.

   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
10. 8.

    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 younger than about 300 million years
    • It is older than 300 million years, since it cuts deep
    • It formed this century
    • It is exactly 300 million years old
11. 9.

    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?

    • Ammonites became extinct first; ichthyosaurs lasted much longer
    • Both groups still live in those seas
    • Ichthyosaurs became extinct first; ammonites lasted longer
    • The three layers formed in one year
12. 10.

    Midnight at the start is Earth forming; the next midnight is today. On the same 24-hour day, when do modern people appear, about 300,000 years ago? Ari works it out.

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