Plate Tectonics

What I Learned About Plate Tectonics

Plate Tectonics Blog Post

The link below is related to the article Duarte, Joao & Schellart, Wouter. (2016). Introduction to Plate Boundaries and Natural Hazards. 10.1002/9781119054146.ch1.:

This link is the AGU book where the article is found. It can be accessed as an ebook:

This is the link to an informative video from Sci Show:

I found this article, which aggregates the two topics of plate tectonics and geological hazards neatly. I also found this video from my favorite YouTube channel called SciShow, which I found it relevant to share. This channel has other informative and straightforward videos from other science courses too.

First, I learned that the association of tsunamis with earthquakes was brought by the Greek philosopher Thucydides, but it was forgotten time by time. It was after the great Lisbon earthquake in 1755 that many philosophers started to suspect the distinguishable relationship of natural causes and God’s punishment to humanity. The magnitude (Mw) of this earthquake was estimated to be around 8.5 to 9, which also produced a tsunami. I found it interested that the Portuguese authorities at that time ordered a survey to the population, and centuries later it was important to the birth of seismology. However, according to the article, it was after 200 years of this event that the plate tectonics theory emerged. Also, I learned that initially, it was believed that there would be twelve lithospheric plates instead of seven.

Second, I learned that plate boundary has an essential relationship with the magnitude of causing natural hazards like earthquakes, volcanic eruptions, and tsunamis. Divergent plate boundaries are characterized by two plate tectonics moving apart and by regions where lithospheric material is created. Convergent place boundaries are more likely to occur high magnitude of earthquakes, thrust faults, and volcanism due to the collision of continental plates or when the oceanic plate is subducted below another plate. A great example is the 2004 Sumatra Earthquake. Transform plate boundaries happen when two plate boundaries slip against each other horizontally. This can produce small to large earthquakes, for example, the 8.4 magnitude earthquake in 1941 in Azores-Gibraltar. Also, megathrust earthquakes like the 1964 Alaska earthquake are the most powerful, and it occurs at subduction zones. This earthquake had a magnitude of 9.2 and produced gigantic tsunamis. I also learned that tsunamis are more correlate with subduction zones where the convergence of two plates happens, and a vertical uplift of the seafloor can cause water displacement. Importantly, as shown in the video, “plate boundaries are just one type of fault or fracture in the crust, and earthquakes can occur far from plate margins.”

Third, I learned that geological hazards are divided into two categories — geophysical hazards, which include earthquakes, tsunamis, hurricanes, floods, and fires. A second category is biological hazards where usually happen after a geophysical event and comprises pandemic spreading of viruses or the contamination of watercourses. A good example is the spreading of diseases after a tsunami.

A final consideration of these resources is the number of geological hazards events that I did not know before reading the article. A good example is the 1755 great Lisbon earthquake, the megathrust magnitude 9.5 Valdivia earthquake in Chile, and the eruption of the Lake Toba supervolcano Indonesia!

Tectonics and Geo-Hazards

I found this following article from the USGS. It’s from 1999 but still interesting and there were a few things I learned.

Three interesting things I found:

  1. Many people believe that the next earthquake on the San Andreas Fault will cause part of California to sink into the ocean or split off into an island or something else ridiculous. But, this region is only a strike-slip boundary. I didn’t realize though that the fault only penetrates 15km through the crust here. I would have thought, since it’s a boundary between two plates, this fault would extend all the way through the lithosphere. Perhaps its too ductile below this point and the plate boundary becomes less defined.
  2. Tsunamis are commonly generated by earthquakes along subduction zones. Caused by the seismic displacement of water, they can travel as fast a jetliner at around 800km per hour! Volcanic eruptions in areas like subduction zones can also cause tsunamis as in the case of Krakatau in 1883. The tsunami the eruption caused alone killed more than 36,000 people and reached 7000km away.
  3. Volcanoes (a common feature along subduction zones and divergent boundaries) are responsible for nearly 300,000 deaths since 1600. They can also have global impacts on climate. The 1991 eruption of Mount Pintubo cooled some areas by up to .5 degrees C due to the large volume of material delivered into the atmosphere. In 1815, Indonesia’s Tambora volcano caused a 3 degree drop in global temperature.


Three things I learned about plate tectonics and hazards

1) I learned that the Red Sea was made because of the African plate splitting. I thought it was because there was a divergent boundary
between the African and Arabian plate, but I suppose it could be caused by both the divergent boundry and the African plate splitting. On that note, I also didn’t know that the lakes made from splitting plates are called “Linear Lakes.”

2) I learned that there is a difference between a hazard, a disaster and a catastrophe and that they are not synonyms.
-A hazard is a natural process that poses a threat to human life or property. The event itself is not a hazard; but becomes a hazard when it threatens human interests. So if an earthquake occured no where near human property and no lives were lost, it’s just that: an earthquake.
-A disaster is the effect the hazard has on society. “Disaster” is used when the interaction between humans and a natural process results in property damage, injuries, or loss of life. An earthquake results in some property damage, some lives lost, so that earthquake is now a disaster.
-A catastrophe is a massive disaster with significant deaths, injury, and economic loss. An earthquake totaled a city, millions of dollars of damage and hundreds of lives lost. It’s now a catastrophe.

3) I learned that natural disasters are getting worse and that is a combination of climate change and because of human growth. The example they give demonstrating the later, is the 7.0 Haitian earthquake in 2010 vs the 9.1 Japanese 2011 earthquake. The Haitian earthquake was a catastrophe (100,000-300,000 deaths) because of poor living conditions and building codes but while the Japanese earthquake was also a catastrophe (<16,000 deaths), but not on the same level as the Haitian earthquake. The example given in regards to the climate change is the desertification that caused the famine in Somolia from 2010-2012 that killed 260,000.