Plate Rifting

I promised to never talk about myself, but I guess after over three years of not writing anything, I should give some sort of pitiful excuse.  I was in my freshman year of college when I last wrote, and have been busy taking some horrifically difficult and time consuming classes.  Honestly, I've been writing so many papers and taking so many tests, I just haven't had the time to do it.  I'm currently at James Madison University and will graduate December 2017 with a BA in Dance, a BS in Geology, and minors in Geophysics, Math, and Italian.  I'm a TA in the geology and physics labs and have been doing research this past year.  Next year, I'm doing research to model Venusian mantle convections and volcanism, and I'm going to field camp in Iceland  with the South Dakota School of Mines and Technology to study volcanoes this summer.

Enough about me.  Let's talk about plate rifting.  This will be part of a two post series about the Wilson Cycle, which is a simplification of plate tectonics.  Information for this article comes from the past several long years of studying for Dr. Lynn S. Fichter's tests and his website (Wilson Cycle Dr. LS Fichter).

Beneath a stable content, rifting begins when mantle convections cause a buildup of heat and pressure.  The hotspots cause upwelling in the continent, which eventually cracks into a triple junction, or three rifts radiating from the hotspot.  An example of this is shown in the image below, where the Red Sea and the Gulf of Aden are two of the arms (the third being on land and not doing anything in particular) of the triple junction.

When rift arms of a series of triple junctions connect, rifting over the continent begins to occur.  Magma from the mantle continues welling up, pushing the continental crust upward, thinning and stretching it.  Eventually, the continents are entirely separated, with mafic igneous rock between them.  As the igneous rock cools, it sinks below the sea level, and water begins to fill the space between the continents, the beginnings of a new ocean.

The upwelling of the magma in the rift leads to a new convection cell within the mantle.  The hotter, less dense material is brought up towards the rift, as cooler, denser material farther from the rift sinks in order to fill in its place.  The convection cell carries the continents away from the rift as the magma rises up between them.

The Mid-Atlantic Ridge is a beautiful example of a rift.  Running down near the center of the Atlantic Ocean, the Mid-Atlantic Ridge is the point where upwelling is driving the European and North American plates away from each other.  The rift produces spectacular volcanoes, such as those found in Iceland, and an entire special suite of rocks called an Ophiolite Suite.

Rifting is one of the fundamental concepts of plate tectonic theory, and it's really cool to understand how oceans are born.  In my next post (which will be within the next three years), I'll talk about the closing of an ocean basin in order to provide a more complete understanding of plate tectonics.