The Earth's Inner Core has an Inner Core!

image credit: NASA Goddard Space Flight Center

     Do you teach Earth Science or have you ever built a model of the layers of the Earth? You might want to rethink your lessons and layers! Research published today in Nature Geoscience indicates that there might be more to the core of the Earth than we once thought. It turns out that the inner core of our planet might actually have an inner core of its own!  
     Researchers at the University of Illinois and the Nanjing University in China used seismic waves from earthquakes to analyze what is actually far below the Earth's surface. Seismic waves are the vibrations made when an earthquake or explosion occurs. Studying the way the waves move and resonate as they travel through the Earth is a good way to understand the material that the wave passes through. As we can't actually travel inside the Earth, scientists have been using seismic waves to understand the Earth's interior for quite some time. Until now it was thought that the inner core was a solid ball of iron. In this recent study, researchers saw that there was a distinct inner core within what we've known as the inner core. The difference of the two regions of the inner core is that the iron crystals in the outer portion are oriented north-south, while some of the iron crystals in the innermost portion are oriented roughly east-west. This is significant because it might shed some light on how the Earth was formed and how it is evolving.

     This new information about the Earth's core follows research published last December concerning the inner core. University of Michigan researchers theorized a new model that would resolve some long unanswered questions about the chemical make-up of the core. The model indicates that two-thirds of the Earth's carbon might be stored within the inner core, essentially making it the biggest carbon sink on the planet! The researchers will indeed need to do further testing to determine how accurate the model is. Just like the inner-inner core study, their testing will involve analysis of seismic waves that help to indicate the materials of the interior parts of the Earth. This discovery would also shed some light on the early development of the planet.

     Are you ready to shift your thinking and include an inner-inner core in your Earth models? Let's hope they find a less confusing name for it! This is a great way to study how scientists must make inferences to learn about things they cannot actually observe. I could see inferences and shifting theories being an interesting future discussion topic in your classroom and at home.

Read more:

• EurekAlert!: "Earth's surprise inside: Geologists unlock mysteries of the planet's inner core"
• Phys.org: "Most of Earth's carbon may be hidden in the planet's inner core, new model suggests"

Earth's Core Activities and Resources:

• Edible Earth Model (Your challenge is to add the new "inner, inner core"!)
• Exploratorium: Model Seismic Waves with a Slinky
• Shake it Up with Seismographs- Build a simple seismograph
• Annenberg Learner- A Closer Look: Mapping Earth's Interior
• NeoK12- Earth games and activities for kids

Good books for discussing observations vs. inferences, click for more info: