Wednesday, June 6, 2018

Guatemala's Volcanic Eruption

The eruption of a volcano in Guatemala and its tragic consequences have drawn attention across the globe this week.  Some will blame the event on the random violence of nature while others will see the hand of God in the destruction and suffering.  But if you must accuse someone or something, blame the Atlantic Ocean.

During the Permian Period, some 250 million years ago (MYA), the Continents had merged to form Pangea.  By the Triassic, about 200 MYA, the Tethys Sea opened, separating Laurasia (the northern Continents) from Gondwanaland (the southern Continents).  Then, during the Jurassic Period (some 150 MYA), the Atlantic began to open and the American Continents were pushed westward, a process that continues today.  In concert, the oceanic Farallon Plate was forced to subduct beneath the advancing Continental Plates; today, the Juan de Fuca Plate (in the Pacific Northwest), the Cocos Plate (west of Mexico and Central America) and the Nazca Plate (west of South America) are the primary remnants of the Farallon Plate and all continue to subduct beneath the American Plates.

As these oceanic plates subduct, their leading edge melts when it approaches the Earth's mantle, triggering the formation of volcanoes (the Cascades, the western mountains of Mexico and Central America, and the Andes); earthquakes and tsunamis also result from this tectonic activity.  The current eruption in Guatemala, releasing volcanic ash, pyroclastic flows and lahars, is thus a secondary effect of the Atlantic's expansion.  Earth did not stop evolving when we humans appeared!