Friday Headlines, September 20, 2013
THE LATEST IN THE GEOSCIENCES
The biggest volcano on Earth!
A mantle hotspot could explain the New Madrid seismic zone.
Nanotyrannus might just be a juvenile Tyrannosaurus rex.
Shatsky Rise is a mountain range on the Pacific Ocean floor close to Japan. It’s height is due to a series of huge volcanoes that erupted between 130 and 145 million years ago. One of the largest and tallest features along the Shatsky Rise is called the Tamu Massif. Until recently, it was unclear if the Tamu Massif was the product of several smaller volcanoes or one huge one.
This new research shows that the Tamu Massif is, in fact, one huge volcano that rivals Olympus Mons, Mars’ largest volcano, in size.
Tamu Massif (and Olympus Mons, and other, more familiar volcanoes like those of the Hawaiian islands) is a massive shield volcano, so named for their resemblance to the round shields used on the battlefield in days of yore.
Shield volcanoes are broad and flat, formed by eruptions of low-viscosity lava that is able to travel a great distance from the vent.
From December 1811 to February 1812, the region near New Madrid Missouri with hit with four devastating magnitude 7 or greater earthquakes.
The middles of continents are strange places for there to be earthquakes, the vast majority occurring along plate tectonic boundaries. There are no active plate tectonic boundaries in the New Madrid area.
So why were there these earthquakes? Why were they so powerful?
Some have hypothesized that there is an ancient fracture zone there, where once there was a plate boundary. About 750 million years ago, a rift existed in this area. North America was being torn in two. Since then, the two pieces of North America have sutured back together, but the weak part remains.
Even though it is no longer an active plate boundary, the old faults that remain still occasionally slip. This is because the entire continent continues to be under stress. The old faults are a weak spot that allows the stress to be relieved.
According to the headline above, a newly discovered hot spot in the Earth’s mantle could explain earthquake activity in the New Madrid seismic zone.
Hot spots are upwelling heated rocks that come from somewhere low within the Earth’s mantle. This heated rock often finds its way to the surface, forming volcanoes. The Hawaiian Island chain is thought to be the result of a hot spot, as is all the activity in Yellowstone National Park.
Unfortunately, the headline is a little misleading, because the original paper explains how a hot spot that passed under the New Madrid area some 100 million years ago might explain renewed seismic activity back then, not in the modern scenario. But the hot spot, in its passage, did leave behind thinner, weaker, and warmer crust that is more prone to fracture, and thus earthquakes.
Nevertheless, it is interesting that a 750 million-year-old closed rift can be re-activated some 600 million years later and then left weak and prone to earthquakes in the modern era.
Ok. I admit dinosaurs isn’t my thing, but this is cool, and an illustration of how the science of paleontology works.
You’ve all heard of Tyrannosaurus rex, the tyrant lizard king. Well, there’s this other dinosaur called Nanotyrannus, which lived at the same time as Tyrannosaurus, and looks a lot like Tyrannosaurus, but is a lot smaller.
When Bakker and others in 1988 named Nanotyrannus, one of their main distinguishing characteristics was its much smaller size. They also observed that the bones of the skull were fused together, indicating that the animal was an adult – basically a very small Tyrannosaurus. There were a few other differences as well, but they decided to call it a new species because of its distinctive size.
The specimen of Nanotryannus was re-described by Carr in 1999. After careful scrutiny, Carr showed that the bones of the skull are not fused, and thus the specimen is a juvenile.
When Carr went into great detail comparing the skull of Nanotyrannus to that of Tyrannosaurus, showing that Nanotyrannus is in fact a juvenile Tyrannosaurus.
Thus, Nanotyrannus isn’t a real animal and it never was. The name is invalid.
You can read all the details over on Thomas Carr’s own website, here.