One of my favorite disaster movies has got to be ‘The Core.’ It has a suitably large amount of big visual scenes to get you in, some unfathomably – and thus probably inaccurate – science and the majority of the rescue crew die.
It’s the way these movies should be, and for once, it deals with something just a little off center.
Or, possibly, totally on center?
OK, that was bad, so I’ll apologize, but the point is, we don’t often hear much about the very center of our planet. As children we assume we can tunnel straight through to China (or your own regional opposite). But as we grow up, we normally just assume that it’s doing what it should be doing.
Well, whether its deactivation is near, or even remotely possible, we at least know what it is now.
“For many years, we have been like blind men touching different parts of an elephant,” said University of Illinois geologist Xiaodong Song. “Now, for the first time, we have a sense of the entire elephant, and see what the inner core of Earth really looks like.”
Being reported in a paper recently accepted for publication in the journal Earth and Planetary Science Letters, geologists from the U of I have confirmed just what Earth’s innermost core is, and its existence (apparently it was up for debate).
The team used both newly acquired data as well as legacy data from around the world to probe the shape of Earth’s core.
From the U of I release: In their analysis, Sun and Song used a three-dimensional tomography technique to invert the anisotropy of the inner core. They parameterized the anisotropy of the inner core in both radial and longitudinal directions. The researchers then used a three-dimensional ray tracing method to trace and retrace the seismic waves through the inner core iteratively.
What they found within the larger core was a distinct change in the inner core anisotropy, ie, the property of being directionally dependent. This change clearly marked the presence of an inner inner core with a diameter slightly less than half the diameter of the inner core; approximately 1,180 kilometers in diameter.
“To constrain the shape of the inner core anisotropy, we needed a uniform distribution of seismic waves traveling in all directions through the core,” Sun said. “Since the seismic waves we studied were generated by earthquakes, one challenge was acquiring enough seismic waves recorded at enough stations.”
The Earth’s core as a whole is composed primarily of iron. We have known that the core consisted of a solid inner core about 2,400 kilometers in diameter and a fluid outer core about 7,000 kilometers in diameter. In The Core, the rescue team was sent to the heart of our planet to revitalize the fluidic outer core. However, it is the solid inner core that is an integral part in the geodynamo that generates Earth’s magnetic field.
The solid inner core, though is elastically anisotropic. In other words, seismic waves travel at varying speeds depending upon which direction they travel. This anisotropy has previously been found to change with hemisphere and radius. However, in this latest work Song and postdoctoral research associate Xinlei Sun depict another anomaly; the inner inner core.
“Our results suggest the outer inner core is composed of iron crystals of a single phase with different degrees of preferred alignment along Earth’s spin axis,” Sun said. “The inner inner core may be composed of a different phase of crystalline iron or have a different pattern of alignment.”
Although the anisotropy of the inner core was proposed 20 years ago, “this is the first time we have been able to piece everything together to create a three-dimensional view,” Song said. “This view should help us better understand the character, mineral properties and evolution of Earth’s inner core.”
Reality is so much cooler than the movies, although, maybe not as sexy (blatant reference to Hilary Swank).
Joshua Hill, a Geek’s-Geek from Melbourne, Australia, Josh is an aspiring author with dreams of publishing his epic fantasy, currently in the works, sometime in the next 5 years. A techie, nerd, sci-fi nut and bookworm.
