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?

   • Whichever layer is thickest
   • The coal on top, since it is the youngest layer there
   • The shale with the same trilobite
   • The conglomerate at the bottom
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
   • 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
5. 3.

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

   • Rocks holding it formed in the same short span
   • It shows which layer is on top at each of the two sites
   • It shows the two sites were once touching
   • 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?

   • Disagree: dinosaurs lived after people
   • Agree: cartoons and movies often show them living together
   • Disagree: those dinosaurs were extinct about 66 million years before 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?

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

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

   • Disagree: fossils show nothing about age
   • 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
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, then the dike, then D
   • Layers A, B, C, D, then the dike
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 exactly 300 million years old
    • It is older than 300 million years, since it cuts deep
    • It is younger than about 300 million years
    • It formed this century
11. 9.

    Midnight at the start is Earth forming; the next midnight is today. Squeeze Earth's 4.5 billion years into one 24-hour day. When does Zee find that dinosaurs (other than birds) became extinct?

    • Seconds before midnight, alongside the first people
    • At about 6 p.m.
    • At about 11:39 p.m.
    • At about noon
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
    • Shelled animals were there from the very start of the day
    • Life has been the same since midnight