AAAS Science Assessment ^beta

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.

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.

Students are expected to know that:

1. The earth’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.

Students are expected to know that:

1. Continental plate material makes up continents, oceanic plate material makes up ocean basins, and the top part of any plate can be made of either oceanic or continental plate material or continental plate material in some places and oceanic plate material in other places.
2. Continental plate material is made of rock that is less dense and much thicker than oceanic plate material.
3. When two plates press together, if one plate has plate material at its edge that is less dense than the edge of the other plate, the less dense plate material will crumple upward, creating a bend or fold in the plate material but not causing the plate to break into smaller pieces of rock. If the plate material is approximately the same density on both edges, the edges of both will crumple upward.
4. When continental plate material from one plate presses against oceanic plate material from another plate, the continental plate material crumples up over the oceanic plate material.
5. As continental plate material from one plate presses against continental plate material from another plate, the edges of both plates crumple up, creating a bend or fold in the plate material but not causing the plate to break into smaller pieces of rock.
6. The result of a plate crumpling up is mountains, which are composed of the continental plate material that has been folded upward.
7. The crumpling up of plate material reduces the area of the earth’s surface covered by a plate.
8. New mountains have formed throughout earth’s history, and mountains continue to develop as plates move and press together.

Boundaries:

1. Students are not expected to know that continental plate material from one plate can sink under other continental plate material from another plate.
2. Students are not expected to know that when two plates press together, plate material breaks (e.g., faults occur) as well as bends.

Students are expected to know that:

1. When two plates pull apart from each other, melted rock rises up between the plates.This rock solidifies as it cools, adding new oceanic plate material to the edges of both plates so that the plates are always in contact with each other and no space forms between them.
2. The process of melted rock rising up between the plates can be gradual, with the melted rock material slowly welling up between the plates, and it can be sudden, with melted rock material suddenly projecting out from between the plates in volcanic eruptions.
3. Melted rock can well up or erupt anywhere along the boundary where two plates are pulling apart.As the melted rock cools, it begins to form a row of mountains along the edges of both plates where they are pulling apart.
4. When two plates move apart and split a continent in two, an ocean basin forms between them that widens over time.The ocean basin grows as new plate material is continuously added to the edge of the separating plates.
5. At the same time that new plate material is being added as plates pull apart, other plate material is being folded upward or recycled into the interior of the earth so that the plate material that is lost in one place is balanced by the new plate material that is gained in another.

Boundaries:

1. Students are not expected to know why some oceanic plate material is denser than other oceanic plate material.

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