Down, Down, Down into a Burning Ring of Fire... Volcanoes, Earthquakes, and Tsunamis, Oh My! (Photo Credit: Mega Documentários Blogspot)

A powerful 7.8 magnitude earthquake sent many Alaskans staggering out of bed at 1230 am last week and triggering a tsunami warning shortly thereafter, a common occurrence for locations along the Ring of Fire. The Ring of Fire is a long string of volcanoes and seismic activity along the Pacific Ocean, stretching from New Zealand, Japan, Russia, Alaska, and down the coast of North and South America. About 90% of the world’s earthquakes occur along this semicircular ring. The Ring of Fire is made up of huge tectonic plates (or slabs of the Earth’s crust) that fit together like pieces of a puzzle. The plates are constantly moving atop a layer of solid and molten rock (called Earth’s mantle) and may crash into each other or move one on top of the other. As the pressure builds, the fault ruptures as the plates snap back to their original place and release that energy in the form of an earthquake.

The epicenter of this particular earthquake occurred 175 miles southeast of Kodiak, Alaska on January 23, 2018. At least 60 aftershocks and the sounds of warning sirens prompted communities in Kodiak, Seward, and Sitka to evacuate amidst a tsunami warning. Coastal areas along Washington, Oregon, California and Hawaii were under a tsunami watch.  After about 4 hours, all tsunami warnings and watches were canceled due to smaller wave heights than expected. The highest recorded waves were about half a foot near Old Bay Harbor.

But, why didn’t this earthquake trigger a bigger tsunami? When an earthquake ruptures, the displacement of the seafloor causes the water above it to also become displaced. The movement causes waves to travel in all directions at the speed of a jet plane, just as ripples are created when a rock is thrown into a pond. This earthquake was a strike-slip event near the Aleutian Trench, where the Pacific Plate and North American Plate slid past each other horizontally with no large vertical displacement of the seafloor.  Although a strong earthquake like this one has the potential to cause a large tsunami, the amount of water displaced by horizontal movement of the crust is limited and the chance of a larger tsunami in this case less likely

It is thought that in a changing climate, earthquakes and tsunamis might become more frequent. Small changes in the mass of the Earth’s surface and even weather patterns may have an effect on volcanic activity due to the recession of ice. With the weight of the ice pushing down on the crust, taking that ice off could trigger earthquakes as the crust bounces back up and releases that pressure. Even over the last 100 years, faults in Alaska have become more active with the loss of ice and moving as the accumulated strain is lifted.

To learn more about the Ring of Fire and central/ eastern Pacific Ocean, please click here!

© 2018 Meteorologist Sharon Sullivan