Deep Earthquakes, Part 2

Last week we started talking about the recent earthquake that occurred bellow the Sea of Okhotsk (950 miles north of Japan).  What was incredibly striking about this earthquake was how deep it was.  Usually earthquakes only go to a certain depth and then stop because of the tremendous pressure of the earth above it pushing down on the lower layers.

Remember that this earthquake is happening because an oceanic plate (the Pacific plate in this instance) is sinking below another plate.  Of course, where you have oceans you have water that gets involved in whatever is going on and plate tectonics under the ocean is no exception.  Water the most awesome substance I know of (water is actually the topic of the latest issue of CCK which will be released shortly, Lord willing).   If magma inside of a volcano is exposed to water it can make the eruption much more explosive.  This happens because water turns to steam at a relatively low temperature compared to other substances.  Similarly, if water gets trapped in the sediments of an ocean plate as it is getting subducted under another plate, the water turns to steam because of both heat in the mantle and heat from the friction of the sinking plate.  Try to picture this: a huge hunk of rock is being forced down below the surface while a surge of steam is trying to work its way up and out of the heat.  This actually causes the plate to sink down faster.

This idea applies mostly to more shallow earthquakes, so scientists still don’t know exactly how earthquakes as deep as the one below the Sea of Okhotsk  get that deep.  Scientists think that maybe heat from the friction caused when a subduting plate slides under another plate makes some of the plate melt (it has to get pretty hot to melt rock -we are talking about hundreds of degrees F).  Like the water, this would make the subduucting plate sink down faster, resulting in what we call “runaway subduction”.   Dr. John Baumgardner and others have used the idea of runaway subduction as it would apply to the global flood of Genesis.

According to the journal “Science”, the already subducted part of the plate being relatively cold (as compared to surrounding mantle) could be the main reason why this earthquake was able to get so deep.  With this idea of a “cold” subducted plate, the earthquake would act more like a shallow earthquake as we see.  A “cold” plate also brings up an important point.  Plates don’t stay “cold” for very long when surrounded by the hot mantle.  If the plate had really begun subducting millions of years ago, we would expect the subducted plate’s temperature to be closer to the surrounding mantle’s temperature.  This fits the Biblical model of a young earth much better.  There will be more on this incredible earthquake next week before we talk about a more tropical subject.

Reference: Clarey, Tim.  (2014, January). Runaway Subduction and Deep Catastropic Earthquakes.  Acts & Facts 43(1), 18-19.  Institute for Creation Research.  Dallas, TX.