Learn It
To read a scientific text successfully, it is important that you do the following:
- Always read more than once – first to get the main idea and then again to identify and record important details.
- Take notes so you can identify important details and revisit them later.
- Look for parts of the text where the quantitative information is needed to support or further explain what is being conveyed by the qualitative information.
Read the following excerpt from the IRIS article “Plate Boundaries”opens in new window. As you read, pay attention to both the qualitative and quantitative details that are bolded. Then, view the “Schematic Cross Section of Plate Tectonics” diagram on page 1 (created by USGS.gov) and answer the questions that follow.
Plate Tectonics
Plate tectonics theory describes how the lithosphere of the Earth is broken into various plates. These plates drift on the asthenosphere at very slow rates. As plates move away from each other the lithosphere thins and tears. At these divergent plate boundaries new oceanic lithosphere is created in the gaps from upwelling magma from the mantle. This upwelling magma forms mid-ocean ridges, long mountain chains that mark the boundaries between diverging plates.
The static size of the Earth implies that crust must be destroyed at about the same rate it is being created. Plate tectonics provides the mechanism to recycle the Earth’s crust. Destruction (recycling) of crust takes place along convergent boundaries where plates are moving toward each other, and sometimes one plate sinks (is subducted) beneath another. The location where the sinking of a plate occurs is called a subduction zone. A transform boundary is where plates slide past each other with no creation or destruction of lithosphere.
Plate Margin Examples
There are three general types of plate boundaries: divergent, convergent, and transform. Each general type has multiple ‘species’: divergent boundaries can be spreading ocean ridges or continental rift zones; convergent boundaries can occur between two oceanic plates, an oceanic and continental plate, or between two continental plates.
Now, go to the article and view the diagram titled “Schematic Cross Section of Plate Tectonics”opens in new window (created by USGS.gov) and answer the questions below.
