Dots show seismic activity along the Mid-Atlantic ridge (thin red line), including today’s two instances (orange dots) | Map courtesy of

The west African country of Liberia monitored (in consultation with the U.S) an earthquake measuring 6.8 on the Richter scale. The event occurred approximately 880 kilometers off the coast of Liberia, early August 18, 2017 at 2:59 a.m., according to the Government of Liberia, though the Ministry of Information, Cultural Affairs and Tourism (MICAT). The second incident took place this afternoon further away into the coastal sea.

MICAT notes that the earthquake incident poses no immediate threat of a tsunami occurring, but cautions that citizens should remain alert.
According to the US Geological Survey today’s early-morning earthquake is the 5th closest occurring off the coast of Liberia, but has the highest magnitude (6.6, according to USGS) among the closest.  Also, five of the closest seven earthquakes offshore Liberia occurred in 2016 alone.  The following earthquakes were recorded by USGS, in order of proximity (closest first):
  • April 14, 2016, at 16:44:33, 5.2 magnitude
  • July 4, 2016, at 10:52:52, 4.9 magnitude 
  • December 12, 2016, at 20:53:46, 4.7 magnitude 
  • November 5, 2015, at 03:19:27, 4.2 magnitude
  • August 18, 2017, at 02:59:21, 6.6 magnitude
  • September 14, 2016, at 09:18:25, 4.8 magnitude  
  • August 20, 2016, at 20:11:43, 4.6 magnitude
According to the Liberian Observer, apart from these seven, at least another 22 earthquakes have occurred offshore Liberia in the same vicinity, all taking place as early as 2015. The second earthquake today in the same vicinity, at 4.8 magnitude, which occurred this afternoon at 15:35:55 (3:35 p.m.), is the ninth in proximity to Liberia.
The Mid-Atlantic ridge is an extensive underground mountain range that runs between three main plates on the ocean floor.
“The Earth’s crust continuously forms along a network of oceanic spreading centers that circle the globe,” explains the University of California, San Diego website. “As new seafloor forms, the earth’s tectonic plates move apart in opposite directions at these spreading centers. As the tectonic plates move apart, rock is pulled up from depth at the spreading axis and melts as it depressurizes. The molten rock rises to the seafloor and cools to form the layer of crust that paves the ocean floor.”
The tectonic plates moving apart on the Atlantic ocean floor are the North American plate (moving westward), and the Eurasian and African plates (moving eastward). The result is a big scar down the center of the Atlantic Ocean where magma is rising up from the mantle to fill in the gap that is being created.


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