how do we know what is inside the earths structure when the total depth we have drill is only 12 miles?

Answer 1

The heart of our planet is largely a mystery because scientists can't go there or see what's inside. Geologists have just one tool, seismology, with which to probe the inner Earth.

The contents of the tool bag just doubled.

For the first time, researchers have detected tiny particles called geoneutrinos coming from deep within the Earth. The discovery is expected to shed light, almost literally, on the contents and processes of the planet's insides.

''There are still lots of theories about what's really inside the Earth,'' said Giorgio Gratta, a physics professor at Stanford University and part of the 87-member team that made the discovery. ''We're doubling the number of tools suddenly that we have, going from using only seismic waves to the point where we're doing essentially simple-minded chemical analysis.''

The findings are detailed in the July 28 issue of the journal Nature.

The hidden core

Earth's core is incredibly hot and dense. The outer part of the core is thought to be liquid, while intense pressure forces the inner core of iron to be solid. The exact composition of the core and the lower reaches of the mantle, which surround the core, are not known.

Peering Inside

Geoneutrinos detected by KamLAND (left) and the Earth's structure (right).




"We only know essentially the crust of our planet," Gratta explained. "Beyond a few kilometers, you simply don't have access.''

For years, Gratta and others have sought to see deep inside Earth by watching what comes out. Scientists know the planet is heated in two ways. Leftover heat from the planet's formation is stored in the core and released gradually. Second, the radioactive decay of rocks releases heat. Scientists do not know how much heat each process contributes.

But they know how important the question is. The inner heat drives volcanic activity and the shifting crust, which leads to earthquakes. Heat sculpts the planet.

Here's what turned out to be useful: When rocks decay radioactively, subatomic particles called geoneutrinos are released.

Particles representing the decay of uranium and thorium, specifically, were detected in the new experiments by a Japanese apparatus called KamLAND.

Deep impact

Neutrinos are invisible and nearly weightless, so they penetrate deeply through nearly all material. Spotting them is incredibly difficult.

The detector used in the new study is buried under a mountain, to shield it from other neutrinos that arrive from space. It consists of 2,000 specialized light sensors inside a 59-foot (18-meter) balloon filled with, in lay terms, baby oil, benzene and a fluorescent stuff. When a geoneutrino interacts with the cocktail, it emits little flash of light.

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Over the past two years, the setup spotted about one of the elusive geoneutrinos a month. Each geoneutrino carries a signature of its chemical origin.

Larger detectors, which might be built in future decades, could pick up a geoneutrino every day and help scientists pin down the planet's deepest activity.

"The first detection of geoneutrinos from beneath our feet is a landmark result," University of Maryland researcher William McDonough writes in an analysis of the discovery for the journal. "It will allow better estimation of the abundances and distributions of radioactive elements in the Earth, and of the Earth’s overall heat budget."

While the new tool could revolutionize our understanding of Earth, textbooks won't be rewritten overnight.

"Before the revolution really comes to fruition, I think it'll take some time," Gratta cautioned, "I would imagine one or two decades, before we have more of those detectors and maybe larger ones built in the appropriate place for geophysics.''

source: http://www.livescience.com/forcesofnature/050727_earth_neutrinos.html

Answer 2

A good question. Most of the info we've got about the mantle and outer and inner core is from seismic (earthquake) waves. For instance, a quake produces both p waves (compression waves like sound vibrations, which can travel through liquids and gases as well as solids) and s waves (shear waves, like wiggling a rope from side to side, which can only travel through solids). When there's a quake, seismographs on the opposite side of the world only record the p waves, demonstrating that there must be a liquid core blocking off the s waves. We know there's a solid inner core because of subtle effects that occur when p waves cross solid/liquid interfaces. The way shock waves are refracted (bent) as they travel through the Earth tells us about the density and rigidity of the mantle and core. Experiments with high-pressure tools like the diamond anvil pressure cell, and at high temperatures tell us how materials must behave in the conditions deep inside the Earth. The Earth's magnetic field is generated deep underground, and it gives us information about conditions down there.

Answer 3

The way sound waves travel through the earth depends on the structure of the earth itself. We can tell that the center of the earth must be liquid based on the type of waves that pass through it and the type of waves that get reflected by it.

Answer 4

Seismology. We know how quickly waves travel through various materials, so we can extrapolate timed waves through the Earth to determine the structure.

Answer 5

1. the effects of gravity can be calculated which tell us how dense the earth must be given it's known size;
2. the behavior of seismic waves through the earth indicate the presence and apparent densities of various layers

Answer 6

they use a seismograph to measure sound.. we also know that as depth increases so does temperature... if we do drill through the crust of the earth and it is hollow there go the oceans...

Answer 7

Check this out!

http://earth.usc.edu/geol125/EarthStructure.pdf#search='what%20is%20inside%20earth'

Answer 8

lol good point