Geocentric Science

The Earth’s plates move as a result of convection currents within the mantle. The moving plates create earthquakes where the plates meet and where they are ripped apart. (Refer to the Earthquakes article).

There are three types of plate boundaries. These include:

1. Convergent Plate Boundaries

   • Two or more tectonic plates come together (the plates converge). Crust is destroyed and earthquakes occur.

   • What are the different types of convergent boundaries?

     Answer:

     A. Continental Crust and Oceanic Crust converge. Since continental crust has a lower density than oceanic crust, the continental crust is forced upwards in the collision and the oceanic crust subducts (is forced downwards). An oceanic trench is created. As the oceanic crust is forced downwards into the mantle it begins to melt. The melted rock (magma) will rise to the Earth’s surface to create volcanoes. The continental crust buckles and crunches as it collides with the oceanic crust and is forced upwards to create mountains. The highest mountains in the world are created this way.

     B. Oceanic Crust and Oceanic Crust converge. Since both slabs of crust are equal in density, both slabs of crust subduct. This plate boundary creates some of the deepest trenches known. As the subducting crust is forced into the mantle, it will melt. The hot plum of magma will rise towards the Earth’s surface (due to the lower density), and create a volcano. The continental crust crunches and buckles as it collides with the oceanic crust. The continental crust is forced upwards to create mountains.

     C. Continental Crust and Continental Crust converge. Since both slabs of continental crust are equal in density, and both are relatively light, neither slab subducts. Instead, both are forced upwards. This type of plate boundary creates extremely high mountains.

   • What are examples of convergent boundaries?

     Answer:

     A. South American Plate is colliding with the Nazca Plate (Continental Oceanic Plate Boundary)

     B. The Philippine Plate is colliding with the Pacific Plate (Oceanic Oceanic Plate Boundary)

     C. The Eurasian Plate is colliding with the Indian-Australian Plate to create the Himalayas (Continental Continental Plate Boundary)

2. Divergent Plate Boundaries

   • Two tectonic plates are pulled apart (the plates diverge). Crust is created and earthquakes occur.

   • What are examples of a divergent plate boundary?

     Answer: The Pacific Plate is moving away from the Nazca Plate to create the East Pacific Ridge.

     Indian-Australian Plate is moving away from the Antarctic Plate to create the Southeast Indian Ridge.

     The Eurasian Plate is moving away from the North American Plate to create the Mid-Atlantic Ridge. Iceland was formed as a result of volcanic eruptions along the plate boundary. In April 2010, there were a series of significant volcanic eruptions. The volcanic eruptions caused air traffic problems, and airplanes were not allowed to fly due to the huge amount of ash and volcanic debris in the air traffic lanes. The Boston Globe has some great images of the eruption.

3. Transform Plate Boundaries

   • Two tectonic plates grind past one another (they become offset). Crust is not created and not destroyed. Relative shallow and larger magnitude earthquakes occur.

   • What are examples of a transform plate boundary?

     Answer: The San Andreas Fault (west coast of the United States), and the Enriquillo Fault in the Caribbean (created the Earthquakes in Haiti in January 2010 Haiti Earthquake)