## Key Idea: The earth's plates move very slowly, pressing against one another in some places and pulling apart in other places.

Students are expected to know that:

1. The earthâ€™s plates move continuously and very slowly (several inches per year) along with the slightly softened layer of rock beneath them.
2. The motion of the plates results in the motion of all things that are part of the plates (e.g., continents, ocean basins, mountain ranges) and all things that sit on top of the plates (e.g., soil, ocean sediment, living things, and buildings).
3. Because the slow motion of plates is continuous, it can result in plates moving great distances across the surface of the earth over very long periods of time.
4. The direction of motion is different for different plates, and the direction of motion of a plate can change over time so that where a plate once pushed into another plate, it can later pull away from that plate.
5. Because different plates move in different directions, plates can press together, move away from each other, and move alongside (parallel to) each other.
6. It is possible to measure the rate of motion and direction of motion of a plate.

Boundaries:

1. Students are not expected to know the terms that describe the different ways plates interact with each other at plate boundaries (e.g., convergent, divergent, transform).
2. Students are not expected to know the forces that act on plates to cause them to move in one direction or another or that plates do not always move as a uniform block (i.e., that different parts of a single plate can move at different rates and in different directions).
3. Students are not expected to know how the rate of motion of plates is measured.
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number
6–8
9–12
Select This Item for My Item Bank

66%

75%

62%

68%

50%

51%

42%

47%

40%

41%

38%

38%

38%

36%

Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

6–8

9–12

PTM123

Continents only move inches over hundreds of years, not feet or miles (AAAS Project 2061, n.d.).

34%

39%

PTM084

Continents and ocean basins move, but so slowly that they will barely have moved after hundreds of years (AAAS Project 2061, n.d.).

34%

39%

PTM128

Earth's plates move by floating on a layer of melted rock (AAAS Project 2061, n.d.).

33%

38%

PTM127

Continents would only move inches over millions of years, not feet or miles (AAAS Project 2061, n.d.).

31%

33%

PTM083

Ocean basins do not move (AAAS Project 2061, n.d.).

29%

30%

PTM122

Ocean basins move separately from earth's plates (AAAS Project 2061, n.d.).

27%

25%

PTM032

Plates move when the layer below them temporarily melts and moves (AAAS Project 2061, n.d.).

22%

21%

PTM126

Continents move so slowly that even after millions of years the distance they moved cannot be measured (AAAS Project 2061, n.d.).

17%

17%

PTM117

Earth's plates move several feet per year (AAAS Project 2061, n.d.).

18%

14%

PTM124

Continents move miles over hundreds of years (AAAS Project 2061, n.d.).

19%

14%

PTM119

Continents move separately from earth's plates (AAAS Project 2061, n.d.).

15%

14%

PTM031

Continents do not move (Ford and Taylor, 2006; AAAS Project 2061, n.d.).

13%

10%

PTM118

Earth's plates move several miles per year (AAAS Project 2061, n.d.).

11%

10%

PTM125

A continent would not move at all over 100 years (AAAS Project 2061, n.d.).

10%

9%

PTM120

Continents moved in the past, but they are no longer moving (AAAS Project 2061, n.d.).

11%

5%

PTM121

Ocean basins moved in the past, but they are no longer moving (AAAS Project 2061, n.d.).

10%

6%

PTM082

Earth's plates do not move (AAAS Project 2061, n.d.).

8%

8%

PTM035

The plates do not move because they sit on a layer of solid rock (AAAS Project 2061, n.d.).

6%

5%

Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.