Untitled Flashcards Set

Chapter Introduction

Introduction

The Zagros Mountains in western Iran consist of a series of anticlines and synclines, formed by compressive forces resulting from the collision between the Arabian and Eurasian plates.

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Imagine it is the day after Christmas, December 26, 2004, and you are vacationing on a beautiful beach in Thailand. You look up from the book you’re reading to see the sea suddenly retreat from the shoreline. Within minutes of this unusual event, a powerful tsunami will sweep over your resort and everything in its path for several kilometers inland. In the next few hours, the coasts of Indonesia, Sri Lanka, India, Thailand, Somalia, Myanmar, Malaysia, and the Maldives will be inundated by the deadliest tsunami in history and more than 280,000 people will die.

Seven years later, on March 11, 2011, a catastrophic 9.0-magnitude earthquake struck Japan, killing more than 13,000 people and leaving thousands injured and homeless. This destructive earthquake also generated a tsunami, one that sent walls of water crashing into the northeastern shores of the island, causing further damage and causalities.

Now go forward to June 2018, when the Fuego volcano, located approximately 44 km southwest of Guatemala City, Guatemala, erupted numerous times with devastating results. These eruptions sent dense ash plumes as high as 6 km into the atmosphere, blanketing the surrounding area with thick layers of volcanic ash. Heavy rains turned this ash into hot (as high as ), raging, volcanic mudflows, some as much as 40 m wide and 5 m deep, flowing down rivers and valleys, and burying everything in their paths. As a result of these mudflows, at least 110 people were killed and 12,578 people evacuated from areas around the volcano.

What do these three tragic events have in common? They are part of the dynamic interactions involving Earth’s plates. When two plates come together, one plate is pushed or pulled under the other plate, triggering large earthquakes such as the 7.0-magnitude earthquake that killed an estimated 223,000 people in Haiti in 2010 and the 7.1-magnitude earthquake in Mexico in 2017, resulting in 370 deaths, mostly from collapsing buildings. In fact, from 2000 to 2016, an estimated 802,000 people have died from 5.0- to >8.0-magnitude earthquakes.

As the descending plate moves downward and is assimilated into Earth’s interior, magma is generated. Being less dense than the surrounding material, the magma rises toward the surface, where it may erupt as a volcano. It therefore should not be surprising that the distribution of volcanoes and earthquakes closely follows plate boundaries.

If you are like most people, you probably have only a vague notion of what plate tectonic theory is. Yet, plate tectonics affects us all. Volcanic eruptions, earthquakes, and tsunami are the result of interactions between plates. Global weather patterns and oceanic currents are caused, in part, by the configuration of the continents and ocean basins. The formation and distribution of many natural resources are related to plate movement, and thus have an impact on the economic well-being and political decisions of nations. It is therefore important to understand this unifying theory, not only because it affects us as individuals, and as citizens of nation-states, but also because it ties together many aspects of geology.