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.

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

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

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

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

   • Agree: cartoons and movies often show them living together
   • Agree: their fossils are in the same layers
   • Disagree: those dinosaurs were extinct about 66 million years before people
   • Disagree: dinosaurs lived after people
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
   • Disagree: the top layers are the oldest
   • Agree: thick layers like these can form in one rainy season
8. 6.

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

   • Agree: each fossil shows its own year
   • Agree: bigger fossils are older, so their size tells the age
   • Disagree: index fossils narrow the age; radioactive dating gives numbers
   • 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?

   • Layer D, then C, B, A, then the dike
   • The dike first, then layers A, B and C, then layer D
   • Layers A, B, C, D, then the dike
   • Layers A, B, C, then the dike, then D
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
    • Ammonites became extinct first; ichthyosaurs lasted much longer
    • Both groups still live in those seas
    • Ichthyosaurs became extinct first; ammonites lasted longer
11. 9.

    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.

    • In the very first hour, just as the Earth formed
    • About 6 seconds before midnight
    • At about 11:39 p.m., with the dinosaurs
    • At about noon, halfway through
12. 10.

    On the 24-hour day, animals with hard shells appear around 9 p.m., about 539 million years ago. What does that show Bo about life on Earth?

    • People appeared right after them
    • Most of Earth's history passed before shelled animals
    • Life has been the same since midnight
    • Shelled animals were there from the very start of the day