Download Open file

School of Forensic and Investigative Sciences
Assessment Coversheet
Module Code
Module Title
Student’s name
Student ID Number
Course/ Subject
Assignment
Title/
Number
FZC010
Module Tutor Tina Gornall
Physics
Rosie Bowers
G 2
0
6
2
5
2
Foundation Applied Science
9
How does the analysis of P-waves and S-waves in the inner core,
outer-core, mantle and crust allow scientist to determine how the
Earth’s interior is structured?
‘I confirm that this piece of work which I have submitted is all my own work and that all
references and quotations from both primary and secondary sources have been fully identified
and properly acknowledged in footnotes and bibliography.’
Signature:
RBowers
Extension
Agreed date:
Date:
23/3/15
Submission
Deadline
Double line-spaced, on A4 paper
In Arial or Times New Roman font in black ink
Learning Outcomes To be completed by the
student
An ability to describe and apply key physics
principles necessary for study on university
level programmes
An ability to present and analyse scientific
data and formulate conclusions
General comments:
27/2/15
Extension
Agreed by:
Work submitted should be presented in the following format:


7
Module Tutor Feedback
Grade*
Rosie Bowers
Strengths:
Areas for improvement:
If there is something you do not understand or some aspect on which you want further information, and
you have not yet had the opportunity, you must make an appointment with your tutor to discuss this
assessment and the feedback given. You may be asked to use this feedback to reflect upon your personal
development (PDP). Upon receipt of the feedback from your module tutor, please complete below your
reflections on this assessment for your future action.
1
1st Marker Signature
Moderation signature**
Date
Date
Word Count: 755
Rosie Bowers
How does the analysis of P-waves and S-waves in the inner core, outer-core,
mantle and crust allow scientist to determine how the Earth’s interior is structured?
(1) The earth is made up of 4 aligned layers: The inner and outer core, mantle
and crust. The crust is the solid surface layer that is made up of tectonic plates.
These plates can move and when this occurs pressure is release causing an
earthquake. Earthquakes produce P (primary) and S (secondary) seismic waves
called as a result. These waves pass through the earth.
(2) The P and S wave movement is recorded by a seismometer. A weight with a
pen or other writing device is suspended above a sheet of paper. When the
earthquakes occurs the seismometer will pick up the tremors and the pen will
write to produce a seismograph. In a professional seismometer a lever is used to
magnify the signal so that even the smallest earthquake can be recorded. The
seismograph will give an indication of the severity of an earthquake. (3) P waves
are longitudinal and will reach the seismograph station first and the s waves will
be detected second as they are transverse.
https://www.sciencenews.org/sites/default/files/images/quakes_followthewave_bottom.png
Scientists can also use P and S waves to determine the medium of the earth’s
interior layers. (4) As P waves are longitudinal they are the faster of the two
seismic waves. They travel by compression and rarefaction of the particles in the
earth. As a result they can travel through both the solid and liquid mediums but
travel a lot slower through solids than liquids. (2) P waves travel through the
mantle at less than 6km h-1 where as they travel at up to 13km h-1 in the core. (3)
P waves are also slightly refracted when the medium changes due to this scientist
are able to determine that there is a change of medium from the mantle to the
inner core.
2
Word Count: 755
Rosie Bowers
(3) S waves on the other hand, are transverse. They travel by movement of
particles and so are the slower of the two. They do not transmit through liquid
medium and so the inner core cannot be penetrated by S waves. S waves will
however pass through the mantle this provides scientist with evidence to suggest
that the outer core is not a solid structure. As S waves cannot pass through the
liquid outer core a ‘shadow zone’ is formed. This is sections of the earth surface
in which S waves aren’t detected. This was used to determine the radius of the
core of 3470m.
Both types of seismic waves, P and S will pass through the mantle and crust
layers suggesting that these two structures are very similar in medium. The crust
is a solid structure. It is the basis of the earth’s surface and therefore P and S
waves will pass through. The mantle is a molten formation that is seen when
volcano erupt. It has properties of a liquid and a solid. Due to the solid properties
of the mantle S waves can pass through it. The inner core however cannot be
penetrated by S waves but P waves can pass through.
(4)
http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/Images_specific02/p_rays.gif
(4) The speed and refraction of the P waves allows scientist to see the changes
of state from solid to liquid throughout the earth’s interior but they cannot tell
scientists much about the state in which it passing through. It merely tell the
scientist that as the depth increase and the P waves travel further into the earth,
the velocity of the wave is alters. As shown by the graph below. And so by
observation of volcanos and the lava they spew, scientist were able to determine
that the structure of the mantle was molten. The graph also show that beyond the
outer mantle the S waves cannot go any further. As it is known transverse waves
3
Word Count: 755
Rosie Bowers
cannot travel through a liquid and so outer core must be a liquid structure. The
graph also suggest that the inner core structure is in fact a solid structure due to
the change in velocity from the outer to the inner core.
(4)
http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/Images_specific02/prem.gif
To conclude, using P waves alone cannot tell a scientist much about the earth’s
structure as they pass through the crust to inner core. It simply tells them that it
is made up of more than one state. The use of S waves in the determination of
the structure tell us a little more about the states that the layers consist of due to
the impenetrable outer core.
4
Word Count: 755
Rosie Bowers
Bibliography.
(1)
BBC
(2014) P
and
S
waves, Available
at:http://www.bbc.co.uk/schools/gcsebitesize/science/21c/earth_universe/seismi
c_wavesrev1.shtml(Accessed: 23rd March 2015).
(2)
USGS
(Sept
2014) Seismometers, Available
at:http://earthquake.usgs.gov/learn/topics/seismology/keeping_track.php (Acces
sed: 23rd March 2015).
(3) The Royal Society Of Chemistry (1996) Structure of the Earth, Available
at:http://www.rsc.org/Education/Teachers/Resources/jesei/waves/home.htm (Ac
cessed: 23rd March 2015).
(4) CJ Ammon (Jan 2010) Seismic Waves and the Earth's Interior, Available
at:http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/ (A
ccessed: 23rd March 2015).
5
Word Count: 755