Thread: Dividing the earth by physical properties?

I am learning earth science and part of my notes say:

The earth, by physical properties, is divided into 3 key regions:
-lithosphere
-asthenosphere
-core

Is the above correct?

I don't understand why the earth is divided into lithosphere, asthenosphere, and core.
And where does the mesosphere go? (lithosphere + asthenosphere + core isn't the "whole" earth)

This might help:

http://pubs.usgs.gov/publications/text/inside.html

Some other references that I found on the internet says the earth's interior (by physical properties) is divided into 5 regions (lithosphere, asthenosphere, mesosphere, outer core, and inner core) and some says 2 regions (lithosphere, asthenosphere)!

However, the one in my notes says 3 regions (lithosphere, asthenosphere, core), I feel quite strange, and also the mesosphere is missing...

With resepct Kingwinner, could you perhaps be confusing the earths layers with the layers of the atmosphere? Here is an additional link:

csep10.phys.utk.edu/astr161/lect/earth/atmosphere.html

Compositionally the Earth has three distinct zones:
Core - Iron-nickel
Mantle - Basic silicate comparable with the igneous rock peridotite
Crust - a 'scum' of mixed composition, but simply divided into a discontinuous upper portion, generally granitic, (forming the continents) and a globe spanning lower portion, generally basaltic, (forming the ocean floor).

Structurally the Earth has five zones.
Solid - inner core
Liquid - outer core
Solid - lower mantle - mesosphere
Plastic - upper, but not uppermost, mantle - aesthenosphere
Solid - Uppermost mantle and crust- lithosphere

As CyndiLoo points out the mesosphere is part of the atmosphere, but it is also used to describe the lower mantle.

Remember that all classifications are artificial: they are used to help us understand relationships between things. They are not real in themselves.

Edited to correct the fact that I can't tell the difference between five and six,when the time is between 1 and 2.

For the mesosphere part that I have mentioned, please see the figure:
http://faculty.weber.edu/bdattilo/sh...s/cmpstrct.htm

The earth, by physical properties, is divided into 3 key regions:
-lithosphere
-asthenosphere
-core

I don't get how these 3 regions have different physical properties...

Thanks Ophiolite! You are very good at organizinag information in a manner that makes it exceptionally understandable and functionable!

Originally Posted by kingwinner

I don't get how these 3 regions have different physical properties...

When you say "how" do you mean "in what way", or "why", or both, or something else? Thanks.

Thank you for your comments CindiLoo. Inasmuch as they are true any skill probably arises from trying to teach intelligent, well educated, alpha males that they are actually quite ignorant. :wink:

I mean "in what way"

According to you, structurally the Earth has only five zones, as you have listed, right?

Thanks!

Please allow me to slide in another question:

Some websites says that the inner core is 1228km thick while other says the inner core's radius is 1228km, which one is correct? The word "thick" kind of confuses me...
Does 1228km thick simply means the diameter of the inner core (sphere) is 1228km?

Originally Posted by kingwinner

According to you, structurally the Earth has only five zones, as you have listed, right?

Quite right. I incorrectly wrote six. I've edited my original post. Thanks.

Originally Posted by kingwinner

I mean "in what way"

The core is pretty uniform in its composition, and, as we have seen, is a mixture of iron with some nickel. There will be a scattering of other minor elements also, and probably a little sulphur. So, you have this largely elemental mass that is liquid in it outer portion (because of the high temperature) and solid in the inner portion (because of the high pressure).
Its two major influences on the Earth are:
a) a significant contribution to its mass [if it were smaller we would be lighter]
b) generation of the magnetic field by a dynamo effect from currents moving in the outer, liquid core

Moving right up to the crust, it is composed of lighter minerals that have migrated there via volcanic eruptions over the last four billion years. The bulk of this is composed of various kinds of silicate minerals. Because it is cool it is also fairly rigid.

Between the crust and the core is main bulk of the Earth, the mantle - this is also composed mainly of silicate minerals, but they are more basic than the crust (they have less silica, the same material most sand grains are made from).
Now the upper part of the mantle is still cold enough to be quite rigid, so it is 'attached' to the crust. These together (upper mantle and crust) make up the lithosphere.
Go a little deeper and the temperature is high enough that the rock becomes semi-molten. The lithosphere 'floats' on this and the blocks it is divided into, the lithospheric plates, move around on this semi-molten mantle. It is the aethenosphere.[Plate tectonics.]
Go deeper still, and although it is getting hotter the pressures are such that the mantle becomes properly solid again.

Hope that helps.

Edit: Just seen your added question. Think about the thickness of the crust - it is the distance from the bottom of the crust to the top of the crust. Same for the mantle. Same for the core. But in the case of the inner core the 'bottom' of the core is the centre of the Earth. Consequently, thickness and radius, in this instance, are the same.

Thanks for the smile!

Thanks a lot! :wink:

"Because the earth rotates, the outer core spins around the inner core and that causes the earth's magnetism."

How come the spinning of the OUTER core gives earth's magnetic field? And why not the INNER core? Does the INNER core spin, too? If so, why?

I don't know where you got that quote, but it is faulty. Both the inner and outer cores spin at almost the same rate as the rest of the planet. A very slight difference in rotation rates exists between the inner and outer cores, but this was confirmed only in the last couple of weeks.
The inner core is solid, the outer core is liquid. Both are predominantly iron, with nickel and a handful of other elements. The Earth's magnetic field is generated by convection currents in the outer core.

Edited to correct errant typography.

Originally Posted by Ophiolite

I don't know where you got that quote, but it is faulty. Both the inner and outer cores spin at almost the same rate as the rest of the planet. A very slight difference in rotation rates exists between the inner and outer cores, but this was confirmed only in the last couple of weeks.
The inner core is solid, the outer core is liquid. Both are predominantly iron, with nickel and a handful of other elements. The Earth's magnetic field is generated by convection currents in the outer core.

Edited to correct errant typography.

Then, what caused the inner core the spin?
Why the spinning of the inner core does not generate earth's magnetic field? (but the outer core does generate)

Originally Posted by kingwinner

Then, what caused the inner core the spin?
Why the spinning of the inner core does not generate earth's magnetic field? (but the outer core does generate)

The inner core is spinning at the same rate (or almost so) as the rest of the planet. The magnetic field is being generated by convection currents in the outer, liquid core.
Kingwinner, I do not intend to be rude, but you are asking a series of related questions that could readily be answered by consulting any of the hundreds (probably thousands) of sites that deal with plate tectonics, magnetism, etc. I can understand asking for clarification of certain points, but you do not appear to referring to other sources at all. It is not my intention to stop you asking questions, but rather to ensure you are pursuing the best of study practices - which appears not to be the case.

I did visit a tons of sites for definitions and explanations, but most of them have no diagrams so I sometimes don't understand. But anyway, I will visit more web sites for information before posting questions next time! Apologies!

Please don't apologise. I don't want you to stop asking questions. Answering them helps me clarify some issues in my own mind and often leads me to turning up something new to me. I just wanted to be sure you were trying the orthodox approaches first.

Originally Posted by kingwinner

Please allow me to slide in another question:

I see you got a nice discussion going on, I hate to interrupt, but I have an important thing to say - I think its a load of BS. Please dont delete my post, but I really think you havnt thought this through... PM me if you think I am wrong about this.