Key Idea: The earth's plates sit on a hot, slightly softened layer of the earth.

Students are expected to know that:

  1. Rocks can be solid, liquid, or in a slightly softened form.
  2. The layer beneath earth’s plates is made of rock that is hotter and less rigid than the plates.
  3. The layer beneath earth’s plates is just slightly softened (just as wax and metal become softened when heated but not yet melted).
  4. The layer beneath earth’s plates moves very slowly and in different directions in different locations around the earth.

Boundaries:

  1. Students are not expected to know that the layer beneath the plates is called the asthenosphere, or that this layer has the properties it does because of pressure being applied to it in addition to the high temperature inside the earth.
  2. Students are not expected to know that the asthenosphere is not uniform and that liquid magma flows through parts of the asthenosphere.
  3. Students are not expected to know how the earth behaves beneath this layer.
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number
Knowledge Being Assessed Grades
6–8
Grades
9–12
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PT017001

The layer beneath earth's plates slowly moves in different directions in different places around the earth.

47%

53%

PT018001

Rocks can be solid, liquid, or in a slightly softened form.

27%

31%

PT016001

The layer beneath earth's plates mostly consists of slightly softened rock.

17%

13%