This archived article was written by: Carlie Miller
The news has been filled with disasters from around to world. Earthquakes, tsunamis, floods, tornadoes, cyclones etc. What takes place after all disasters is the relief and reconstruction and donations of time and money go out to the affected persons. After a period of time, the disaster is forgotten by the rest of the world unless it affected the international economy or took place in a world power country. But did you know that some disasters can permanently affect the world? Even the time you go to bed?
On Feb. 27, an 8.8 magnitude earthquake rattled Central Chile around 3:34. This quake was not the first, nor was it unexpected. Seismic stresses had been building for decades. The temblor was caused by the friction between the Nazca oceanic plate and the South American continental plate. These plates constantly push against one another but the Nazca plate is denser than the South American plate so the result is a convergent plate boundary called a subduction zone (where one plate is pushed under the other into the Earth’s mantle).
This Nazca is being subducted at the Peru-Chile trench which created and continues to build the Andes Mountains. To sound more scientific (and to add more professional words to the article): a subduction zone that increases earthquake occurrences is called a Benioff zone or Wadati-Benioff zone. Chile has a Benioff zone.
Jian Lin, a geophysicist at Woods Hole Oceanographic Institution (WHOI) in Massachusetts, says that the two plates slipped past each other by about seven to 11 meters (approx. 23 to 36 feet). These plates are hitting each other at about three inches every year, “this is one of the fastest plate convergence rates on Earth,” Lin says. Though the plates are moving against each other at a fast rate, they tend to lock together for long periods of time and then release the pressure in short, powerful bursts.
The seism that occurred two weeks ago is one of the strongest earthquakes ever recorded. Since 1900, only four, including the strongest quake (9.5 magnitude in 1960) – which also occurred in Chile – have been more powerful. The 1960 quake caused the tectonic stress to shift to a part of the zone where it locked, building greater pressure. Lin explains that this shifting of stress is probably the cause for the February quake’s early timing (scientists knew it was coming, but thought it would not happen for a while).
Though the Haitian quake was deadlier (due to building collapses) the Chilean quake was 500 times more powerful. In a short six days, the Chile temblor ensued in more than 180 aftershocks (or “after-quakes”) with some above 6.0 magnitude and one 6.9 aftershock was almost as powerful as the Haitian main quake (7.0).
The first part of this article was to give a little history and information behind the Chilean earthquake. Now for the part of the article all have been waiting for – how the Chilean disaster affects our bedtime.
The sudden release of pressure caused a large-scale movement (very large) which shifted an unimaginable amount of rock mass a few feet closer to our Earth’s core. This triggered an increase in the tilt of the planet’s figure axis (the axis on which the planet aligns its mass, not the north-south axis) and thus shortened the day.
Richard Gross, a geophysicist working at NASA’s Jet Propulsion Laboratory in California, says the super subduction caused the Earth’s mass to shift and “just like a spinning ice skater, as she pulls her arms closer to her body, this earthquake moved the Earth’s mass a bit closer to the Earth’s rotation axis and made the Earth rotate a bit faster, just like the ice skater rotates a bit faster.” Because the seism took place in the Southern Hemisphere, the Earth permanently “wobbled” off-balance by approximately three inches.
Just so no one will lose sleep over the fact that Earth has shorter days, the Chilean quake only caused the days to be shorter by 1.26 microseconds (a microsecond is one millionth of a second) so the loss of time isn’t noticeable. For those who think this is anticlimactic, the Sumatran temblor of 2004 (a 9.1 magnitude) shortened our days by 6.8 microseconds, meaning that after time, our bedtimes will truly be affected. So cherish these days by doing something worthwhile – for they are getting shorter and shorter.