How do we know what the Earth's interior is made from?

Answer 1

Every now and then portions of the Earth's interior come out onto the surface. This phenomenon is called a volcano.

Each volcano also puts out as much pollution in a few hours as humans have produced in 500 years.

I think the government should ban volcano pollution and tax all volcanos to buy carbon offsets.

Answer 2

The correct answer to your question is: We do not know with any level of certainty what makes up the earths' core. We have in place, a scientific theory that it is composed of Nickel and Iron (Ni and Fe). And until a new scientific theory disproves this, it is generally accepted to be true.

Periodically we are lucky enough to find material that has been forcefully ejected or risen to the surface. The problem comes in when you try to work backwords from the sample that you have at the surface.

The components of the earth are inner core, outer core, asthenosphere, mantle, and crust. Our deepest probes (usually by exploration for oil) only go 5.5 miles into the crust and we are still miles short of reaching the asthenosphere. The asthenophere is composed of liquid rock. It is this liquid foundation and thermal convection in this layer that drives the theory of plate tectonics.

Our best evidence of the composition of the interior of the earth is generated by seismic exploration (shooting sound waves into the earth and timing how long it takes to return to a sensor on the surface, and volcanism. The volcanism in the Northwest of the US is a fantastic indicator of what the interior of the earth is composed of, but this has extreme limitations. The geologic process that bring material from deep in the earth to the surface is called "subduction zone volcanics" We can analyze magma or lava and break it down into components (oxides) and work back to try to identify the parent source, but during the entire process that produces the volcano the material is subject to assimilation, melting, cooling, temperature changes, etc. that the best chemical work to identify the material is a educated guess, at best.

The lowest point on earth, Marianas Trench in the ocean is still located in the crust and mantle of the earth and does not penetrate the inner core. Without physically going to the bottom of the ocean, then drilling in excess of 5 miles further down and taking a sample, we can only make educated guesses as to the composition of the earth's interior.

Hope this was not to wordy and it helps you....

Answer 3

In addition to some excellent answers on earthquakes or using seismic waves (by the way, radar only penetrates a couple of meters into the ground and sonar is used in the oceans), volcanic xenoliths only show us what the upper mantle (at best) looks like. A common method used to determine the Earth's composition is to look at meteorites, which are presumed to have similar compositions. Meteorites fall into a few categories, with the majority of them being iron-nickel (like the Earth's core) or stony (like the Earth's mantle).

Answer 4

we use mostly seismic studies. when an earthquake occurs the waves from it permeate through the earths mantle. when the waves encounter areas of differing density like the core they get deflected and bounce back in certain ways and become detectable in different areas than they would if earth were the same density throughout. the deflected waves are detected by seismographs, and the results are compared with results from other seismographs around the world. from that information seismologists can determine the angle of the deflected wave and compare that with the waves coming from a known source and figure out where they were deflected and that gives them a pretty good idea where the core is.

Answer 5

Volcanoes erupt material from the interior of the earth, by studying this we can infer the makeup of the deeper layers of earth.

By using radar and sonar to map the interior we can extrapolate the make up down there based on the readings, different substances will effect the signal in different ways.

Answer 6

We were able to find out the interior of earth only after studying the pattern of seismograph recorded during earthquakes.Different layers behaves differently.The reflection ,refraction ,amplification ,change in frequency all helps to determine the earth interiors.See my slide show
My Community in Orkut
http://www.orkut.com/Community.aspx?cmm=26068261
Presentation slides
http://asia.pg.photos.yahoo.com/ph/quake