1. 1. The nature of the earth\'s interior has been determined by both direct (i.
ID: 803267 • Letter: 1
Question
1. 1. The nature of the earth's interior has been determined by both direct (i.e., direct observation of rocks) and indirect (i.e., geophysical) observations.
Direct:
A. (5 pts) One direct observation is a deep drill hole. Where is the deepest drill hole ever drilled (so far) and how deep into the earth did it go?
B. (5 pts) Another direct observation is a deep mine. Where is the deepest mine dug by humans into the earth, how deep is it, and what were they mining to make it so valuable to dig so deep?
C. (5 pts) Another direct observation is the study of fragments of deeper earth materials (xenoliths) brought to the surface through volcanic eruptions and diatremes. What is a diatreme and how deep in the earth do the diamonds come from that they sometimes contain?
Indirect:
D. (5 pts) From Newton’s laws of gravity, we can demonstrate that the ‘average’ density of the earth (i.e., if the entire earth was one density of material) is about 5.52 g/cm3 but the average density of rocks of the continents we see at the surface is about 2.7 g/cm3. What does this tell us about the density of materials that must exist in the earth’s interior in relation to what we see at the surface?
E. (10 pts) The earth has a significant magnetic field that approximates a dipole (N and S magnetic poles like a bar magnet). This magnetic field protects life from damaging solar radiation, and provides an amazing light show (the aurora) when charged particles from the sun are directed along the magnetic field toward the magnetic poles. What about the composition and behavior of the earth’s core, especially the liquid outer core, that helps amplify this magnetic field.
F. Arguably the most informative geophysical method for studying the earth’s interior uses seismic waves, which are manifest as P waves, S waves and surface waves (Rayleigh and Love waves).
a. (10 pts) What is the particle motion of each of these waves (i.e. describe or show a diagram of the way each wave moves through a material), and for what or whom are each of these 4 seismic waves named?
b. (10 pts) S waves do not travel or propagate through a liquid because it has no rigidity. How is this significant for the occurrence of the S wave shadow zone, and over what distances from an earthquake does the S wave shadow zone occur?
c. (10 pts) Both P and W waves refract or bend as they pass across a boundary from one velocity of material to another. How is this related to the P wave shadow zone and over what distances from an earthquake does the P wave shadow zone occur?
Explanation / Answer
A.(5 pts) One direct observation is a deep drill hole. Where is the deepest drill hole ever drilled (so far) and how deep into the earth did it go?
Answer: Kola superdeep Borehole with drill depth 12 kilometers, this is deepest hole on earth.
B.(5 pts) Another direct observation is a deep mine. Where is the deepest mine dug by humans into the earth, how deep is it, and what were they mining to make it so valuable to dig so deep?
Answer:MPoneng Gold Mine in south Africa, depth ranges from between 2.4 km to 3.9 km, they have been mining the gold.
C.(5 pts) Another direct observation is the study of fragments of deeper earth materials (xenoliths) brought to the surface through volcanic eruptions and diatremes. What is a diatreme and how deep in the earth do the diamonds come from that they sometimes contain?
Answer : Diatreme is a long vertical volcanic pipe.Diamonds may formed around 150 km in depth of earth interior and they come by xenoliths
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