Moving plates, and the clues that they move

Grade 6 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   2.5 cm each year = about 25 km each million years; 10 million years. At about 2.5 cm a year, how much wider could the Atlantic be in 10 million years? Esme uses the USGS figure of 25 km per million years.

   • About 250 km
   • About 2,500 km
   • About 25 km
   • No wider; continents are fixed
2. 2.

   Along the San Andreas Fault, two plates slide past each other. Over millions of years, what does Kira predict for towns on opposite sides?

   • They crash together into mountains
   • They swap sides of the fault within one lifetime
   • They slowly shift far apart, sideways
   • They stay exactly where they are
3. 3.

   Luz's friend says Mesosaurus swam across the ocean between Africa and South America. Which response is best?

   • Agree: reptiles can swim great distances
   • Disagree: it walked over a land bridge
   • Disagree: it lived in fresh water; the lands were joined then
   • Agree: the continents have stayed right where they are today, so it swam
4. 4.

   A video says continents race around at kilometers per year. Milo checks USGS. Which response is best?

   • Disagree: plates move a few centimeters a year
   • Disagree: plates do not move
   • Agree: you can watch coastlines move from one year to the next
   • Agree: plates surf fast on liquid lava
5. 5.

   “Cross-section, not to scale:” Noah's cousin says the oldest seafloor is found at the mid-ocean ridges. Which response is best?

   • Disagree: seafloor is one age everywhere
   • Disagree: the youngest is at ridges; it gets older outward
   • Agree: ridges are where the oldest rock slowly piles up in heaps
   • Agree: ridges are where plates crash
6. 6.

   Map of South America and Africa fitted together along their coasts. Which set of clues best supports the idea that South America and Africa were once joined, by Pia's judgment?

   • Both continents have deserts today
   • Animals today can still travel easily between the two of them
   • Both continents have tall mountains
   • Matching coastlines, fossils and rock layers
7. 7.

   “Cross-section, not to scale:” Ren looks for evidence that the seafloor spreads. Which observation is the best evidence?

   • Rock gets older moving away from the ridge on both sides
   • Ridges have no earthquakes
   • The ocean is deepest near the coasts
   • The ridge sits mid-ocean, so its rock must be the oldest there
8. 8.

   Map of a coast with the sea floor offshore unlabeled. Which clue tells Tala that a convergent boundary lies just off a coast?

   • A deep trench with a chain of volcanoes beside it
   • Flat, quiet seafloor with no earthquakes or volcanoes nearby
   • A straight fault with sideways offsets
   • A ridge with brand-new seafloor
9. 9.

   “(teacher only)” The teacher gently warms one side of a pan of thick, gooey liquid with cracker pieces on top, and the pieces drift. What do the pieces stand for, says Ari?

   • Earthquakes shaking the crust
   • Continents floating along on top of a liquid lava ocean
   • Plates that stay fixed
   • Plates riding on slowly moving mantle rock
10. 10.

    Bo pushes two stacks of paper together on a table, and they buckle upward where they meet. Which feature does this model?

    • A transform fault
    • A ridge at a divergent boundary
    • Mountains at a convergent boundary
    • A trench from plates pulling apart