The United States Geological Survey
recorded a Magnitude 4.7 Earthquake at a depth of 36.1 km, about 19 off the south coast of of Big Island, Hawaii, at about 6.05 am local time (about 4.05 pm GMT) on Monday 27 July 2020. This was a
large quake for Hawaii, and was felt across the entire of Big Island, as
well
as on the neighbouring islands of Maui, Kaho'olawe, Lāna'i, Moloka'i,
O'ahu, and Kaua'i, though there are no reports of any injuries or damage
associated with this event.
The approximate location of the 27 July 2020 Big Island Earthquake. USGS.
The islands of Hawaii have formed as a result of hotspot volcanism, with
the hotspot currently located under Big Island, Hawai'i, and each of
the other islands being the result of previous activity from the same
hotspot, with the oldest Islands in the northwest and newest in the
southeast. A volcanic hotspot is an area where magma from deep inside
the Earth is welling up through the overlying plate (in this case the
Pacific) to create volcanism at the surface. Volcanoes move as they
erupt, swelling as magma enters their chambers from bellow, then
shrinking as that magma is vented as lava. The movements of a group of
volcanoes close to one another can place considerable strain on layered
rocks, and the islands of Hawai'i, and in particular Big Island, are
very prone to Earthquakes, though these tend to be small and frequent
rather than large, rare and destructive.
he position of the Hawai'i Hotspot relative to the islands of Hawai'i. Joel Robinson/USGS/Wikimedia Commons.
Witness accounts of quakes can help geologists to understand these
events and the rock structures that cause them. If you felt this quake
(or if you were in the area but did not, which is also useful
information) you can report it to the USGS here.
See also...
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