Plate Motion, Hot Plume Drifting and the Hawaiian-Emperor Volcanic Chain

[Hervé]

What caused the mysterious bend in the Hawaiian-Emperor chain?

GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre
Science Daily
Thu, 08 Jun 2017 00:00 UTC

This Hawaii-Emperor seamount chain.
Credit: University of Sydney

© T. Torsvik et al. (GFZ)

The Chain is an example of a hotspot track - a trail of volcanic islands and seamounts created on a lithospheric plate as the plate slowly shifts over a spot of localized melting sourced by a jet of hot material rising from the deep mantle (mantle plume).

The volcanic islands of Hawaii represent the youngest end of a 80 million years old and roughly 6,000 kilometres long mountain chain on the ground of the Pacific Ocean. The so-called Hawaiian-Emperor chain consisting of dozens of volcanoes is well known for its peculiar 60 degrees bend.

The cause for this bend has been heavily debated for decades. One explanation is an abrupt change in the motion of the Pacific tectonic plate, the opposite model states southward drift of the mantle plume that has sourced the chain since its beginning 80 million years ago. Apparently both processes play an important role, shows a new study in Nature Communications, published by a group of scientists from the University of Oslo, German Research Centre for Geosciences GFZ Potsdam, and Utrecht University.

Many volcanic ocean islands are created by columnar shaped hot upwellings called mantle plumes that originate near the ~3000 km deep base of Earth's mantle. Mantle plumes are not much influenced by surface motions of the tectonic plates that slowly move over them. Hence, long linear chains of plume-sourced volcanoes that get older and older with increasing distance from active hotspots can be tracked for hundreds to thousands of kilometres.

In the Hawaiian hotspot trail, the Hawaii islands are the youngest in the chain that stretches nearly 6,000 km to Detroit seamount in the northwest Pacific, where volcanism occurred about 80 million years ago. An unprecedented 60 degrees bend characterizes the Hawaiian-Emperor Chain, dividing it into the older Emperor Chain and the younger Hawaiian Chain. The bend has been dated to 47 Ma.

"The ultimate cause for the formation of the Hawaiian-Emperor Bend (HEB) was a prominent change in the Pacific plate motion at 47 Ma," says the lead author of the new study, Trond Torsvik from the University of Oslo and visiting researcher at GFZ at the moment. The team affirms a hypothesis by the US-geophysicist Jason Morgan who proposed that already in the early 1970s. "But it is not that simple as it was suggested forty years ago," says Torsvik.

Jason Morgan was the first to use hotspots as a reference frame for global plate motions. In his model mantle plumes -- which are manifested by hotspots at the surface -- were considered fixed in the mantle, and the Hawaiian-Emperor Bend was attributed to a simple directional change of the Pacific plate motion. But his plate model with fixed hotspots became challenged from the 1980s.

"Since the late 1990s it has become clear that hotspots are not totally fixed," says GFZ´s Bernhard Steinberger, one of the co-authors of the paper. That is now generally accepted, he adds, and mantle flow models predict that the Hawaiian hotspot has drifted slowly to the south. "But some recent studies have argued that rapid southward motion of the hotspot before 47 Ma can explain the formation of the bend without requiring Pacific plate motion change," he says. "Such a scenario has become attractive because the geology of the plates surrounding the Pacific shows no clear evidence for a Pacific plate motion change."

The new study shows clearly why this simply does not work. It would require an unrealistically high rate of hotspot motion of about 42 cm/year which would be much faster than the average speed of tectonic plates. Moreover, this would imply that the Emperor Chain was created in just five million years and Detroit Seamount should only be 52 million years old. This prediction is obviously falsified by the recorded Detroit Seamount island ages of about 80 Ma.

"Alternatively, a slower hotspot motion towards the WSW could explain both geometry and ages of the Emperor chain," says Steinberger. However, such a direction of motion is inconsistent with mantle convection models. "Our paper is a good example of how very simple simulations of plate and hotspot kinematics can be used to explore which geodynamic scenarios for the formation of the Hawaiian-Emperor Bend are possible, and which ones are not," says Pavel Doubrovine from the University of Oslo, another co-author on the paper.

"We cannot avoid the conclusion that the 60 degrees bend is predominantly caused by a directional change in the Pacific plate motion." Yet, some southward plume motion is required, otherwise the Hawaiian-Emperor Chain would be around 800 kilometres shorter.

"Explaining the geometry, length and age progression of the Hawaiian-Emperor Chain, requires both: the change in the direction of plate motion and the movement of the hotspot," states Torsvik. "If, after more than two decades of debating the end-member scenarios of plate motion change versus hotspot drift, geophysicists will be able to agree that neither of the two is satisfactory -- then we can move forward and address a more interesting question: what actually drove the Pacific plate motion to change at about 47 million years ago?" Hopefully, it will not take further 40 years to get an answer to this, he adds.

Fig. 2 a: Simulating the Hawaiian-Emperor Bend: A simulation that assumes that the Pacific plate moves with a constant angular velocity to the north-west (8 cm/year). To produce a 60o bend with the Pacific plate not changing its direction and velocity and purely southward hotspot drift (~19o of north-south motion) requires an extreme rate of hotspot motion (42 cm/year), which would imply that the Emperor Chain has been created in just five Myrs and Detroit Seamount is only 52 Myrs old. (b) The yellow line represents the actual track of the Hawaiian-Emperor Chain (as in Fig. 1) and the red line shows a track that would be produced by the motion of the Pacific plate, that changes at 47 Ma, if the hotspot were fixed relative to the mantle. You see that the red line is displaced southward compared with the Hawaiian-Emperor Chain, and that is the effect of southward hotspot drift for the past 80 million years (blue line), which has lengthened the Emperor Chain by about 800 km (blue line; ccby 4.0: Torsvik, T. H. et al. Pacific plate motion change caused the Hawaiian-Emperor Bend. Nat. Commun. 8, 15660 doi: 10.1038/ncomms15660 (2017).

[onawah]

That would be a good question for Dutchsinse, and he would probably answer it in pretty short order.

[wnlight]

Perhaps we need to know what happened to the Earth about 47 million years ago? That is a pretty sharp bend implying a catastrophic event. This would be another heavy blow to the uniformitarianism geologists.

[wnlight]

EDIT: I retract this post. I made an error in interpreting a date. - WNLight

I am going to weave a web of facts, along with some conjecture, into a cataclysmic event that happened some 40,000 years ago. If I am correct, then we may have a very rough and wild ride ahead of us in the next few years. My degree is not in Geology, but rather it is in Mathematics. But I am a student of Geology.

[Note: I lost all my footnotes when inserting this, so i now add them back enclosed in brackets.]

Let me start with the known facts.
“In the Hawaiian hotspot trail, the Hawaii islands are the youngest in the chain that stretches nearly 6,000 km to Detroit seamount in the northwest Pacific, where volcanism occurred about 80 million years ago. An unprecedented 60 degrees bend characterizes the Hawaiian-Emperor Chain, dividing it into the older Emperor Chain and the younger Hawaiian Chain. The bend has been dated to 47 Ma.” This is indication of a drastic change in the Pacific Plate movement. [Trond H. Torsvik, Pavel V. Doubrovine, Bernhard Steinberger, Carmen Gaina, Wim Spakman, Mathew Domeier. Pacific plate motion change caused the Hawaiian-Emperor Bend. Nature Communications, 2017; 8: 15660 DOI: 10.1038/ncomms15660]

“A temporary magnetic pole reversal, the Laschamp event, occurred around 41,000 years ago. It lasted less than 1,000 years with the actual change of polarity lasting around 250 years. The actual polarity changes lasted only 250 years. During this period, the field was even weaker, with only 5% of today's field strength. As a consequence, the Earth nearly completely lost its protection shield against hard cosmic rays, leading to a significantly increased radiation exposure." [Nowaczyk, N. R.; Arz, H. W.; Frank, U.; Kind, J.; Plessen, B. (2012): "Dynamics of the Laschamp geomagnetic excursion from Black Sea sediments" Earth and Planetary Science Letters, 351-352, 54-69. doi:10.1016/j.epsl.2012.06.050]

“The largest volcanic eruption on the Northern hemisphere in the past 100,000 years, namely the eruption of the super volcano 39400 years ago in the area of today's Phlegraean Fields near Naples, Italy, is also documented within the studied sediments from the Black Sea.” There is strong indication that it will soon erupt again. [Nature Communications 7, Article number: 13712 (2016). doi:10.1038/ncomms13712]

Now let's add some deductive reasoning.
1) The bend in the Hawaiian-Emperor chain took very little time. This is deduced by the very sharp angle of the bend. This must have happened during a huge cataclysmic event.
2) Timing of the Laschanp event could be off by 1000 years. If so, then perhaps this pole reversal even could have happened about the same time as the super volcano near Naples,
3) The timing of the bending of the Hawaiian hotspot is not very accurate and could easily be off six or seven thousand years. It could have happened about 40 Ma, or the same time as the other two events.

Conclusion
So, it may have happened that the drop in the Earth’s magnetosphere allowed enough hard cosmic rays to strike the Earth causing a drastic increase of vulcanism that included the strongest super volcano of the last 100,000 years. This could be an artifact of a cataclysmic event caused by a reaction in the Earth’s core, in turn, caused by the large increase of hard cosmic rays striking the Earth.

This conclusion of mine depends on some conjecture, but not enough to be dismissed out of hand. I suggest that this possible chain of events needs be studied in depth. We need to know. This study needs to be done because our Earth is now entering another period of magnetic pole reversal. We may be in for another cataclysmic event that could even be civilization destroying.

[Hervé]

Posted by wnlight (here)
[...]
1) The bend in the Hawaiian-Emperor chain took very little time. This is deduced by the very sharp angle of the bend. This must have happened during a huge cataclysmic event.
2) Timing of the Laschanp event could be off by 1000 years. If so, then perhaps this pole reversal even could have happened about the same time as the super volcano near Naples,
3) The timing of the bending of the Hawaiian hotspot is not very accurate and could easily be off six or seven thousand years. It could have happened about 40 Ma, or the same time as the other two events.
[...]

Warren, unless I missed something, it seems there is a mix-up of a few orders of magnitude in your data:

• age of the Hawaii bend ~ 47 Million years ago
• age of the Laschamp event ~ 40,000 + 1,000 years ago
• age of the Neapolitan super volcano eruption ~ 39,400 years ago

... so that your point # 3 ends up equating 7 million years with 7 thousand years and 40 Million years with 40,000 years to make all three events coeval.


You might want to re-check this thread: Mediterranean Yellowstone: Naples' Campi Flegrei Supervolcano

[wnlight]

Thanks for setting me straight, Hervé. I read 47 Ma as 47 thousand years, the "M" as thousand. Why, I am not sure. So, I have to look further for what else happened at 47 Million years ago to cause the bend.