Key Idea: The outer layer of the earth – including the continents and the ocean basins - consists of separate plates.

Students are expected to know that:

  1. The rock layer beneath the surface of the earth is divided into massive sections of solid rock, called “plates.” The plates fit closely together such that all of the edges of a plate touch the plate next to it.
  2. Plates are miles thick.
  3. The continents and ocean basins are part of the plates. The exposed solid rock of mountains is an example of plate material that is visible when it is not covered by water, soil, or loose rock such as sand.
  4. There are about 12-15 very large plates, each of which encompasses large areas of the earth’s outer layer (e.g., an entire continent plus adjoining ocean floor, or a large part of an entire ocean basin). Together these very large plates make up most of the entire outer layer of the earth. The rest of the outer layer is made up some additional smaller plates.
  5. The boundaries of continents and oceans are not necessarily the same as the boundaries of plates. Some boundaries between plates are found on continents, some on ocean floors, and some in places where oceans and continents meet.

Boundaries:

  1. Students are not expected to know the terms bedrock, lithosphere, crust, or mantle.
  2. Students are not expected to know the names of specific plates, the size of the smaller plates, or how many small plates there are.
  3. Students are not expected to know that the term “plates” refers to the lithosphere, or that two components (crust and upper mantle) make up the plates.
  4. Students are not expected to know that the plates are not uniform in composition or thickness.
Frequency of selecting a misconception

Misconception
ID Number

Student Misconception

Grades
6–8

Grades
9–12

PTM104

Earth's plates are located deep within the earth and are not exposed at the earth's surface (AAAS Project 2061, n.d.).

53%

52%

PTM013

Plates are feet thick (AAAS Project 2061, n.d.).

49%

43%

PTM011

Plates are made of melted rock (AAAS Project 2061, n.d.).

40%

39%

PTM078

Earth's plates are separated by empty gaps (AAAS Project 2061, n.d.).

29%

40%

PTM103

The solid rock of a cliff is not a part of a plate (AAAS Project 2061, n.d.).

31%

30%

PTM096

The earth has seven plates (AAAS Project 2061, n.d.).

31%

28%

PTM010

There is one continent on each plate (AAAS Project 2061, n.d.).

31%

28%

PTM005

Plates are arranged like a stack of layers in the earth. (Libarkin et al., 2005; Marques and Thomson, 1997; Ford and Taylor, 2006; AAAS Project 2061, n.d.).

28%

N/A

PTM101

Earth's plates are piled on top of each other (AAAS Project 2061, n.d.).

27%

29%

PTM094

Ocean basins are not part of earth's plates (AAAS Project 2061, n.d.).

25%

23%

PTM110

Continents sit on top of a layer of water, and the water is above a plate (AAAS Project 2061, n.d.).

25%

21%

PTM015

The earth has about one hundred plates (AAAS Project 2061, n.d.).

23%

22%

PTM105

Plate boundaries only occur where continents meet ocean basins (AAAS Project 2061, n.d.).

22%

24%

PTM109

Continents are on top of plates but are not part of plates (AAAS Project 2061, n.d.).

22%

24%

PTM099

Earth's plates are not in contact with each other (AAAS Project 2061, n.d.).

24%

20%

PTM095

Continents are not part of earth's plates (Ford and Taylor, 2006; AAAS Project 2061, n.d.).

20%

18%

PTM098

Earth's plates are separated from each other by oceans (AAAS Project 2061, n.d.).

15%

16%

PTM106

Plate boundaries are always found in the middle of ocean basins (AAAS Project 2061, n.d.).

16%

12%

PTM100

Earth's plates are surrounded by melted rock so that the plates are not touching each other (AAAS Project 2061, n.d.).

15%

11%

PTM108

Continents are next to plates but are not part of plates (AAAS Project 2061, n.d.).

12%

11%

PTM012

Plates are several inches thick (AAAS Project 2061, n.d.).

12%

10%

PTM107

Plate boundaries cannot occur within a continent (AAAS Project 2061, n.d.).

11%

9%

PTM102

Earth's plates are made of sand (AAAS Project 2061, n.d.).

10%

8%

PTM097

The earth has one very large plate (AAAS Project 2061, n.d.).

7%

7%

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.