What is the primary evidence that the Earth's outer cores is fluuid in nature?

In summary, the primary evidence for the fluid nature of the Earth's outer core is the Earth's magnetic field and the disruption of seismic waves when one side of the Earth experiences an earthquake.
  • #1
blueyellow

Homework Statement



What is the primary evidence that the Earth's outer core is fluid in nature? (2 marks)

The Attempt at a Solution



The Earth has a magnetic field which is created by molten iron that is moving. If there were a solid outer core, there would be no moving iron and no magnetic field.

Continental drift - all continents are still drifting and creating volcanoes - this includes the edges under the deep oceans.

Is this what one needs to say for two marks, do you think? So is the primary evidence just the Earth's magnetic field? Or can the speed that waves travel at through the outer core also be taken as primary evidence? But what is THE primary evidence? I tried to look this up, but there doesn't seem to be a simple straightfoward answer. Please help. Please do not say that this does not belong in Advanced Physics. This is a question from a third year course and I find it complicated.
 
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  • #2
Look up the difference between p and s waves in seismology.
 
  • #3
I have learned (currently taking an introductory Astrophysics class) that it is shown by measuring the discontinuity of seismic waves. An earthquake on one side of the Earth can be detected at various points on the other side of the Earth but on directly the opposite earthquake (as well as in a certain distance radially outward from that point), those detections are disrupted. P-type waves, which travel much slower through a liquid, are virtually the same as sound waves. From this we can deduce that there is something at least slowing the wave down in the core. That does not imply it is a liquid, however. S-waves, which deal with a shear force interaction (side to side like when you pull a card out of a deck of cards and others come out with it), are not present in the area on the opposite side of the Earth as I described, a property limited to liquids. By taking various measurements, one can basically isolate what the core looks like.

I also recently read an article saying that models aimed at replicating these effects have proven that our core is not as fully iron as we think. Based on the results of these models, there are theories that silicon or other lighter elements exist in non-negligible quantities inside the Earth's core.
 

FAQ: What is the primary evidence that the Earth's outer cores is fluuid in nature?

1. What is the primary evidence that the Earth's outer core is fluid in nature?

The primary evidence for the fluid nature of the Earth's outer core comes from the study of seismic waves. Seismic waves travel through the Earth and can be used to create images of its interior. These images have revealed that the outer core has a lower density than the solid inner core, indicating that it is likely composed of a liquid material.

2. How do scientists know that the Earth's outer core is not solid?

In addition to seismic evidence, scientists also use the Earth's magnetic field as evidence for the fluid nature of the outer core. The Earth's magnetic field is generated by the movement of liquid iron in the outer core, which is able to create a magnetic field due to its fluid nature. This is further supported by the fact that the Earth's magnetic field changes over time, which indicates that the outer core is constantly in motion.

3. Can the Earth's outer core solidify over time?

While the outer core is currently in a liquid state, it is possible for it to solidify over time. This process is known as core solidification and is believed to be happening gradually over billions of years. However, the exact rate and timing of this solidification process is still a topic of ongoing research.

4. What other evidence supports the idea of a fluid outer core?

In addition to seismic and magnetic evidence, there are other lines of evidence that support the idea of a fluid outer core. One example is the observation of Earth's rotation rate, which has been found to vary over time due to the movement of liquid in the outer core. Additionally, the distribution of elements within the Earth's layers also suggests a fluid outer core, as denser materials would sink to the bottom of a liquid layer.

5. Is there any other known planet with a fluid core?

Yes, there are other known planets with fluid cores, including Jupiter and Saturn. These gas giants have much larger and more massive fluid cores compared to Earth, which is why they are able to generate such strong magnetic fields. However, the exact composition and behavior of these fluid cores may differ from that of Earth's, as they are made up of different materials and exist in different environments.

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