What is an Intraplate Earthquake?

Schematic of location of Nov 30 Anchorage earthquake. Image courtesy Temblor.net

 

Intro:  I wrote this some 12 months ago, a couple months after our M7.1 intraplate earthquake here in Anchorage.  This seems a good time to revisit what happened and why.  As usual, there are more questions afterwards than before.  Cheers –

Volcanoes of Io – Part 2 – The Volcanoes

Galileo 1998 image of Io. This one shows two active plumes. Pillan Patera plume is at the upper limb of the moon. It is 140 km tall. Second active plume is Prometheus Patera center bottom near the terminator between dark and light

Volcanoes of Io – Part 1 – Introduction

Io. Orange is plume deposit around Pele Patera. Multiple patera and plains are visible. Note lack of impact craters meaning the moon is regularly resurfaced. Image courtesy NASA JPL via Sen.com

Makushin Volcano, Alaska. The 9th Most Dangerous Volcano in the US?

Active fumaroles on Makushin Volcano from Dutch Harbor July 2018. Photo courtesy Abi Woodbridge, via AVO

2007 – 2014 Uplift Episode at Laguna del Maule

Laguna del Maule Volcanic Complex. Image courtesy Sernageomin

Usu, Nakajima and the Toya Caldera, Hokkaido, Japan (Hokkaido 1)

Panoramic photo of Lake Toya and Toya Caldera looking west. Nakajima Island(s) are located in the lake in the right portion of the image. Usu volcano is left of the lake straddling the land between the lake to the right and the ocean to the left. Image courtesy Toya-Usu UNESCO Global Geopark

Lago Ilopango – an El Salvador Caldera (updated and reposted)

Ilopango Caldera

 

Update, Aug. 2019:

In the five years since this was first posted, science continues to grind away, answering a few questions which in turn create a bunch more questions.  The Baillie tree ring / ice core team is increasingly of the opinion that the 535 – 540 AD global cooldown was caused by huge volcanic eruptions, at least two of them bracketing the period.  A team including Robert A Dull published a paper August 16 entitled “Radiocarbon and geologic evidence reveal ilopango volcano as the source of the colossal ‘mystery’ eruption of 539/40 CE” that appears to nicely define the most recent end of that bracket.

Shishaldin Volcano, Alaska – Neighbor to Fisher Caldera

Shishaldin from 11 km altitude. Note the steam from the ice-free crater. Image courtesy AVO, Jun 2015.

June 22 Eruption at Raikoke, Kuril Islands

 

NASA ISS photo of Raikoke in eruption taken June 22. Active plume with water vapor collar at the base. Water vapor collar at the base may be due to ambient air sucked upwards with the plume. Alternately, it may be due to interaction of pyroclastic flows with surrounding sea water. Image courtesy NASA Earth Observatory.

Simushir Island – Nested Calderas and Secret Sub Bases, Central Kuril Islands

Simushir Island. Volcanoes named on the image. Photo courtesy Japan Space ASTER, Oct. 2004.