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9.5 Option - Geophysics: 5. The information benefits humans
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5. Geophysics provides information that is of
economic and social benefit
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Students learn to:
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Students: |
Extract from Physics Stage 6 Syllabus
(Amended October 2002) © Board of Studies, NSW.
[Edit 30 June 09]
Prior learning: Preliminary modules 8.2, 8.3, 8.4.
Background: The science of geophysics has enabled the discovery of some of the world's largest ore bodies that were hidden under deep cover of sediments and would otherwise have remained forever undetected. In addition to that use, the network of seismological stations developed during the Cold War has enabled the monitoring of the testing of nuclear weapons because of their unique seismic signature. Environmental monitoring is now routinely performed using remote sensing tools. The scale of that monitoring can vary from the local to regional and even national scale with instruments as simple as hand held spectrometers to as high tech as inferometers on satellites.
identify data sources, plan choose equipment or resources for, and perform an investigation to demonstrate the use of a geophysical method in the field
- You are required to attempt an experiment using a
geophysical technique to discover something about the
subsurface environment.
- You need to identify data sources so
that you are aware of the range of investigations that
could be done.
- You may use electrical resistivity methods, a seismic
refraction method, or something as simple as the use of a
commercial metal detector.
- When you have decided which investigation you are going
to do, you will need to plan the
investigation. The one chosen will largely be
determined by the equipment available to you. Since metal
detectors can be purchased for under $30 this is a cheap
way to satisfy the requirements of this aspect of the
syllabus.
- When you have chosen the equipment and planned the investigation, perform the investigation, carefully recording the results, for example in a table.
explain the benefits of geophysical methods in mineral exploration and environmental monitoring
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Geophysical methods are of benefit because:
- they cost less than conventional exploration or monitoring methods
- they can often be used remotely from the air. This means they have greater area coverage than conventional methods do
- they can be used from satellites hence providing long term and continuous data collection
- the techniques are often non-invasive hence causing no damage to the environment
- the techniques are such that the data collected is readily stored in a digital format so it can be reprocessed by computers to extract additional information with appropriate algorithms
- they can see through cover of either vegetation or sediment to provide data on the subsurface.
describe the role that geophysicists have played in one of the following:
- monitoring nuclear test ban treaties
- natural hazard reduction
Monitoring nuclear test ban treaties
- Seismologists are able to determine when a blast comes
from an explosion and are also able to gauge the size of an
explosion by studying the size and shake directions of the
seismic disturbance caused by the explosion.
- The same data can also serve to pinpoint the location
of any explosion because the shake produced by an explosion
is different from that produced by natural earthquakes.
- Explosions generate seismic waves in all directions
equally whereas earthquakes generate seismic waves that are
predominantly in one plane. A world wide
seismological network of stations has been established by
geophysicists and they are strategically located to
give as much monitoring cover as is possible. Should a
nation choose to break the nuclear test ban treaty it would
be detected almost immediately. This is so even if the
nation attempted to hide the test underground. The Geoscience
Australia (GA)
website reports explosions and you can
check any country's record since 1945.
You can go to the site describing the contribution
of seismology to the Comprehensive nuclear test ban
treaty, Lawrence Livermore Laboratories, Science and
Technology Review, 1998.
Natural hazard reduction
- Because geophysical techniques can often be operated
continuously and remotely the techniques are used in
monitoring situations where there is a danger of landslide
or volcanic eruption. The idea is to use geophysical
monitoring equipment such as sensitive geophones remotely
connected to centralised computer systems to give early
warning of earth movements and potential danger. Remote
sensing satellites can give early warning of potential
weather related hazards.
- See a volcano hazard site that has links to real time
geophysical monitoring of a volcanic natural hazard site at
Long Valley Observatory
US Geological Survey, California,
USA
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