ESRT Page 5 - Tectonic Plates

The locations of plate boundaries are shown on the map above. There are 3 kinds of boundaries:
1) Divergent - Plates are moving apart.
2) Convergent - Plates are coming together.
3) Transform - Plates are sliding past one another.

Dotted lines are used to indicate boundaries that do not fall neatly into a single category.


3 kinds of plate boundaries


Convergent plates


Divergent plates

Where plates converge (red boundaries on map) one plate subducts, dives back down into the mantle, while the other, the overriding plate, moves up and over.

Look for several important features at convergent boundaries:
1) Deep sea trenches:  On the map above you will find trenches at many convergent boundaries: The Peru-Chile trench, the Mariana trench, and the Tonga trench for example.

2) Volcanoes: As the subducting plate enters the mantle it melts. The magma produced is hot and less dense than the rock above so it gradually rises and forms long arcs of volcanic mountains for hundreds of miles along coastlines. Volcanoes can be found at most convergent and divergent plate boundaries. This includes the entire perimeter of the Pacific Ocean known as the 'Ring of Fire'

3) Earthquakes: All plate boundaries are associated with earthquakes. 

Mid-Ocean Ridges: These are under-sea mountain ranges that are formed by rising magma at divergent plate boundaries. The Mid-Atlantic, East Pacific ridge, and Southeast Indian ridge are examples.

REMEMBER: Convergent boundaries = Trenches.
                      Divergent boundaries = Mid-Ocean Ridges

Hot spots are points on the Earth's surface located directly over plumes of magma rising from deep within the mantle. The location of the plumes does not change but over time the plates above the plumes move. A line of volcanoes is created as the plate moves over the plume. One by one volcanoes are created and then become extinct as the plate moves (see video).  Over time this process creates island chains, long lines of extinct volcanoes. Today the island of Hawaii is above a hot plume. Eventually it will  become extinct and a new Hawaiian island will form.
QUESTION: What is the location, latitude and longitude, of the Tasman hot spot? Since the Tectonic Plate map comes complete with latitudes and longitudes it can be used to locate this geologic feature. On the map in your ESRT draw the lines of latitude and longitude that intersect at the Tasman hot spot (see lines drawn on map above). The answer: 37S, 160E.

Practice Questions

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