Page 24 - Laboratory Manual in Physical Geology

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logical possibilities, or working hypotheses (tentative (300,000,000 meters/ second, or 3 * 10 m>s ). The spec-

ideas to investigate, test). It is always best to have more trum is subdivided into bands —parts of the EM spectrum
than one working hypothesis. that are defined and named according to their wavelength
(distance between two adjacent wave crests or troughs).

1. Chalcopyrite may be a pure substance, or chemical
element . What investigating and gathering of evidence Instruments aboard satellites scan information from
could we do to reasonably determine if this is true not only the visible bands of the electromagnetic spectrum,
or false? but also parts of the spectrum that are not visible to humans
(e.g., infrared).The ASTER instrument scans 14 bands
2. Chalcopyrite may be a compound composed of two or of electromagnetic radiation. Bands 1, 2, and 3 are visible

more elements. What investigating and gathering of (blue-green, red) bands (left side, FIGURE 1.1). Bands 4–9
evidence could we do to reasonably determine if this are short wave infrared bands (SWIR) that are invisible to

is true or false? If true, then how could we find out humans (right side, FIGURE 1.1). Bands 10–14 are thermal
which elements make up chalcopyrite? infrared (TIR) bands that are also invisible to humans.
Let us conduct two investigations (activities planned True Color and False Color Images. Data from
and conducted to test hypotheses, gather and record data, environmental satellite instruments must be rendered into
make measurements, or control and explore variables). In an image that humans can see, either by giving objects
Investigation 1, the chalcopyrite is ground to a powder and in the image their true color or a false color. True color
heated. This investigation reveals the presence of sulfur photographs and satellite images show objects in the colors
and at least one other substance. The remaining substance that they would appear to be if viewed by the human
is attracted to a magnet, so it may be iron or a compound eye However, since many bands of radiation detected by
containing iron. When the powder is leached (dissolved in satellites are not visible to humans, the bands are given a
acidic water) and subjected to electrolysis (Investigation 2), false color in satellite images (right side of FIGURE 1.1 ).
copper separates from the powder. The remaining powder
is attracted to a magnet, indicating the presence of iron.
Analysis of the results of these two investigations leads us ACTIVITY
to the logical conclusion that Hypothesis 2 was correct
(chalcopyrite is a compound). The results are also evidence 1.2 Spheres of Matter, Energy,
that chalcopyrite is composed of three different elements:
sulfur (S), iron (Fe), and copper (Cu). Chemists call and Change

chalcopyrite copper-iron sulfide (CuFeS ) . Since chalcopyrite
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contains a significant proportion of copper, it is also a copper THINK | What materials, energies, and processes
ore (natural material from which copper can be extracted at a About It of change do geologists study?
reasonable profit).
This same laboratory procedure is applied on a massive OBJECTIVE Analyze and describe the materials,

scale at copper mines. Because most copper-bearing rock energies, and processes of change within and among
contains only a small percentage of chalcopyrite or another Earth’s spheres.
copper-bearing mineral, the rock is mined, crushed, and
powdered. It is then mixed with water, detergents, and air PROCEDURES
bubbles that float the chalcopyrite grains to the surface of 1. Before you begin , read the following background
the water. When these grains are removed, they are smelted information on matter and spheres, energy
(roasted and then melted) to separate impure copper from sources and sinks, and processes and cycles of
the other parts of the melted chalcopyrite (that cool to form change. This is what you will need :
slag ). The impure copper is then leached in sulfuric acid and ___ Activity 1.2 Worksheets (pp. 27 – 29 ) and pencil
subjected to electrolysis, whereupon the copper is deposited with eraser
as a mass of pure copper on the positive electrode (cathode). 2. Then, follow your instructor’s directions for
completing the worksheets.
Satellite Remote Sensing of Geology
There are times when geologists cannot make
direct observations of Earth and must rely on a technology
to acquire and record information remotely (from a Matter and Spheres
distance, without direct contact). This is called remote Everything on Earth is made of matter and energy.
sensing . One of the most common kinds of remote sensing Matter is anything that takes up space and has a
used by geologists is satellite remote sensing. mass that can be weighed. It is tangible materials and
substances. At the global scale of observation, geologists
Electromagnetic (EM) Radiation. The electromagnetic conceptualize Earth as a dynamic planetary system
(EM) spectrum of radiation is a spectrum of electric composed of interacting spheres (subsystems) of living
and magnetic waves that travel at the speed of light and nonliving materials.

Thinking Like a Geologist ■ 9