Geocentric Science

By the 1960s, there was enough evidence to support seafloor spreading (refer to Evidence of Ocean Floor Spreading). However, scientists also knew that the entire crust was not capable moving in all directions at once if it was a solid shell. The Theory of Plate Tectonics was born in order to explain the movement of the lithosphere and scientists determined that the lithosphere must consist of tectonic plates.

1. What is the evidence that supports the Theory of Plate Tectonics?

   Answer:

   A. The oceanic crust is significantly younger than the continental crust (therefore, the oceanic crust is created and destroyed more quickly than the continental crust).

   B. Earth’s magnetic field has been preserved in the oceanic rock. The rock shows that there have been many magnetic field reversals throughout Earth’s history.

   C. There are three types of plate boundaries: convergent, divergent, and transform. New seafloor is created at divergent plate boundaries (the mid-ocean ridges) and destroyed at convergent plate boundaries (trenches). Therefore, Earth is not getting bigger or smaller (crust is being created at the same rate that it’s being destroyed).

   D. Volcanic activity is associated with plate boundaries, and the Ring of Fire is the result of the plate boundaries that surround the Pacific Ocean. Image from Wikipedia

   E. Convection currents (rising and sinking of magma due to density differences) in the mantle provide the driving force that cause the plates to move.

   F. Convection currents produce hot spots

2. What are tectonic plates?

   Answer: The lithosphere (the Earth’s surface) is broken into large, rigid slabs (or plates) of rock. (There are approximately six large slabs and several smaller pieces.) The plates move independently of one another as a result of convection currents within the asthenosphere.

3. What are hot spots and how do they form?

   Answer: A plume of magma rises from deep within the mantle through the lithosphere. The plume creates a volcano, and as the lithospheric plate moves over the plume of magma, a chain of islands can form. Hot spots are observed in the center of a tectonic plate (away from a plate boundary).

4. What are examples of hot spots?

   Answer: The Hawaiian Islands, the Galapagos Islands, and Yellowstone National Park, formed as a result of a plume of magma rising up from the mantle.