|
Answers Prepared by Wm. D. Underwood, Ph.D., 2009, last updated 2022 This answer
sheet is intended for Geology Merit Badge counselors, parents and
Scouters who need help teaching this merit badge or need to
help struggling Scouts. This
mixture of answers and comments is a supplement to the Merit Badge Pamphlet,
and should not be used as a replacement. It is NOT
intended for Scouts earning the merit badge to use. If you are a Scout you
are on your honor not to use this to help yourself earn the Geology Merit
Badge. Using this is against the
Spirit of Scouting, the Scout Oath, the Scout Law, and the principles and
practice of earning Merit Badges. Resources for both Scouts and instructors are
available on the “Resources” page. Pictures of geologic and Scouting
interest may be found on the “Pictures” page. 1. Define
geology. Discuss how geologists learn about rock formations. In geology,
explain why the study of the present is important to understanding the past. The word “geology”
is derived from the Greek word for Earth (Geo) and story (logos). Geology is the story of Earth. Geology is the study of the
materials, processes and history of Earth. The materials involved are rocks, the
minerals that form rocks, and other materials which make up the planet we
live on, Earth. This includes
water, the atmosphere, and many other materials which, at first glance, may
not seem to be in the interest of geologists. Geologists also study the animals
(including humans) and plants that affect Earth. Generally, living things are only of
concern to geologists as they affect Earth or indicate Earth conditions. Fossils are the remains of life in the
geologic past. The processes of interest to
geologists are those that shape the Earth and form, modify, or destroy the
rocks and materials that make up the Earth. Geologists study not only such
processes as mountain building, plate tectonics, earthquakes, volcanism, rock
weathering, and sedimentation, but also other processes such as weather and
global warming which do not fit the layman's idea of geology. Although geology was originally
the study of Earth, it has been extended to other planets. Planetary geology is the study of the
materials, processes and history of extra-terrestrial planets. Since Man has not yet visited other
planets (except the Moon, where a geologist has been), planetary geology
relies heavily on remote sensing (indirect examination from a distance)
rather than on direct examination of geological evidence. 2. Pick
three resources that can be extracted or mined from earth for commercial use.
Discuss with your counselor how each product is discovered and processed. Many Earth resources are used in everyday life. Most people know that metals, whether industrial or precious, are mined and processed. Most Earth resources are not metallic, however. Wallboard is made from gypsum. Concrete requires aggregate and limestone. Bricks and pottery require clay. Although water not a resource that is generally extracted or mined, it is critical to life and required in almost all processes. There must be enough water to drink, bathe, wash our cars, water our lawns, etc. Large amounts of water are also used in industry and resource extraction. In some places there is enough rainfall and surface water for our needs, and we do not need to use significant amounts of underground water. Most wells in these areas draw their water from the ground water supply. This supply is replenished each time it rains, and never moves far from the rainfall area. Other areas require water to be extracted from aquifers far from their recharge areas. As an alternative water can be piped in from regions where water is more plentiful. Oceans cover 71% or Earth’s surface and contain about 97% of Earth’s water. However, this water is highly saline (about 3.5% salt) and cannot be used for most purposes until it is processed. Desalinating water is an expensive process, making sea water impractical to use for most purposes. Waste disposal and pollution are closely related to water supply. If waste is not disposed of correctly, it will get into the ground water and surface water. This water may then become dangerous and require treatment. The more treatment required, the more expensive the water. In the extreme case, the water may be so polluted that it cannot be treated. In this case no matter how much of it there is, it cannot be used, and is no longer part of the water supply. Land use planning is essential to maximize resources and minimize strain on the land and environment. Earth is tough, and recovers from most problems, but recovery takes time. It takes much longer to heal Earth than to disrupt the natural balance. 3. Review
a geologic map of your area with your counselor and discuss the different
rock types and ages of rocks represented. Determine whether the rocks are
horizontal, folded, or faulted, and explain how you arrived at your
conclusion. Sedimentary rocks are deposited horizontally, younger rocks on top of older. Each rock unit is called a formation. After deposition and lithification most rocks are tilted, and often folded and faulted. Then they are eroded to form the current land surface. Geologic maps show the type and age of rocks at the surface. The shape of the boundaries between formations are a combination of the attitude of rocks immediately under the surface and the surface topography. Most geologic maps (in fact most maps) have a legend describing the information portrayed. Rock types are discussed under requirement 5C. A geologic time scale is included at the end of this document. Geologic maps can be found at the National Geologic Map Database (https://ngmdb.usgs.gov). 4. Do
ONE of the following: a. With your parent’s and
counselor’s approval, visit with a geologist, land-use planner, or civil
engineer. Discuss this professional’s work and the tools required in
this line of work. Learn about a project that this person is now working on,
and ask to see reports and maps created for this project. Discuss with your
counselor what you have learned. Many cities have geological or engineering societies made up of professionals. Often local universities or colleges have geology or engineering departments. Most city and county governments have land-use planners. Any one of these groups can suggest a professional who would be willing to talk to one or more Boy Scouts about his or her profession. Your scout may watch this careers video. b. Find
out about three career opportunities available in geology. Pick one find out
the education and explain the education, training, and experience required
for the profession. Discuss this with your counselor and explain why this
profession interests you. College and university faculty are often good sources of information on career opportunities. Professional societies, particularly the national societies, usually have web pages and brochures related to careers in their fields. The American Association of Petroleum Geologists (http://www.aapg.org), the Geological Society of America (http://geosociety.org) and the Society of Exploration Geophysicists (http://www.seg.org) are excellent sources. Your scout may watch this projects video. 5. Do
ONE of the following (a OR b OR c OR c): 5a. Surface and Sedimentary Processes
Option 1. Conduct an experiment approved by
your counselor that demonstrates how sediments settle from suspension in
water. Explain to your counselor what the exercise shows and why it is
important. Several experiments show the settling of sediments in water. Perhaps the easiest is uses a mix of sediments of different sizes from clay through sand or small gravel. A handful of dirt, and handful of sand, and a handful of small gravel works well. Thoroughly mix the sediment in a quart jar full of water and watch the material settle. Note that the larger, heavier grains settle first and the finest grains are suspended for a very long time (days if the grains are small enough). The settling of sediments shows both the erosional and sediment transport capabilities of streams, and the stratification of sediments as they are deposited. The heavier grains, those that settle faster, require fast-moving water to be transported, and are easily dropped when moving water slows. Smaller grains can be transported by progressively slower water. The finest grains are suspended until the water is absolutely calm. 2. Using
topographical maps provided by your counselor, plot the stream gradients
(different elevations divided by distance) for four different stream types
(straight, meandering, dendritic, trellis). Explain which ones flow fastest
and why, and which ones will carry larger grains of sediment and why. (Hint: Use a piece of graph paper to plot stream gradients with distance on the x-axis and elevation on the y-axis.) Stream gradient is the slope of a stream, or the distance downward the water flows compared to the distance it flows horizontally. The steepest gradients produce the fastest streams that in turn carry the largest grains. As a stream’s flow slows it can carry only smaller and smaller sediments, until calm, sluggish water can carry only the finest sediments such as mud. As the term suggests straight streams have very few, gentle curves. Meandering streams have many sweeping curves. In the extreme they have large loops that are almost cut off. Many meandering rivers exhibit oxbow lakes or lunate features, former meanders that have been cut off and partly or completely filled with sediment. Water flow in meandering streams is much slower than in straight streams. Fast-flowing mountain streams become meandering when they hit flatter terrain. The extra length of the stream is needed to accommodate the fast inflow. Dendritic streams are branched, resembling trees. Trellis streams are also branched, but each branch is parallel like a rose trellis. A perpendicular branch usually connects the parallel branches, which enter at a right angle. Trellis streams generally indicate alternating layers of harder and softer rock that has been tilted or folded and eroded. The harder rock forms ridges; the softer rock forms valleys with streams. 3. On
a stream diagram, show areas where you will find the following features: cut
bank, fill bank, point bar, medial channel bars, lake delta. Describe the
relative sediment grain size found in each feature. Wherever a stream turns, particularly on the tight bend of a meander, the water on the outside of the bend flows faster and erodes the bank. This is the cut bank. On the inside of the bend and slightly downstream is the fill bank or point bar. Here sediments are deposited. Sediments in a point bar are usually relatively course-grained, often pebbles or gravel and sometimes sand. Finer-grained sediments continue to be carried downstream. Wherever a stream enters a lake
or the ocean water flow slows and cannot carry as much sediment. The dropped sediment piles up to form
a delta. Deltas generally form
with sand in the channel where the water flows faster and silt or mud at the
edges and at the distal portion where the water is deeper and the current
slows virtually to a stop. Medial channel bars form in the middle of the channel as water flow slows, perhaps when the gradient is reduced or the stream nears a lake or the ocean. Deltas often contain medial channel bars which may be seen as sandbars. Medial channel bars also occur where a stream widens or deepens to form a pool. They may form islands at low stream water levels. 4. Conduct
an experiment approved by your counselor that shows how some sedimentary
material carried by water may be too small for you to see without a
magnifier. This experiment can easily be combined with requirement 5A1. After the course grains have settled, scoop out a little of the murky water from the top of the jar and place it in a shallow dish. Use a magnifying glass to examine the water. What is causing the murky color? If available, a small microscope will give a better picture. Put a drop or two on a slide without a cover, and look at the sediment still suspended in the water. 5. Visit
a nearby stream. Find clues that show the direction of water flow, even if
the water is missing. Record your observations in a notebook, and sketch
those clues you observe. Discuss your observations with your counselor. Streams contain many clues that let a geologist determine the direction of water flow. The first clue is to look along the watercourse. Water comes from the direction that is higher and towards the direction that is lower. Other clues must be used where the watercourse is not steep enough to detect slope. One of the best clues is looking at the sediment patterns. Point bars point downstream. Another clue is the angle a tributary makes when it enters the main stream—the tributary usually enters pointing downstream. 5b. Energy Resources Option 1.
List the top five earth
resources used to generate electricity in the United States.
In the 30 years between 1990 and 2020 the use of coal for electricity reduced from over 50% to under 20%. Meanwhile natural gas more than tripled its share from 12.3% to 40.3%. Recently renewables, hydro, solar and wind, have increased to almost 20% of the electricity generated in the US. Most of this increase is in wind and solar; hydropower has decreased by about 2%. Nuclear has shown little change in the last 30 years. Coal is the oldest industrial fuel. The ready availability of coal in England started the industrial revolution. Coal is one of the most abundant energy sources in the world today. Major deposits of coal are found on all continents. Coal is used in the US primarily in generating electricity and making steel. In the past it has been used to power trains and ships, and to heat homes and buildings. Coal is generally a dirty fuel, and much effort is needed to remove sulfur, ash and other pollutants from the smoke. Coal is a large contributor to climate change, producing more CO2 per BTU than other fossil fuels. 40% of the electricity in the US is now generated from natural gas. Natural gas is abundant and efficient. Coal-fired power plants use boilers to generate steam which turns turbines connected to generators. It takes a significant amount of time to start up a coal-fired power plant. Natural gas, on the other hand, runs turbines directly (like a jet engine). Therefore, they can be turned on or shut down quickly to meet demand. Also, natural gas produces far fewer emissions than coal, generally just CO2 and water. And natural gas produces far less CO2 per BTU than coal. Nuclear power is an important source of electricity in the US and around the world. In Europe, up to 80% of all electricity is generated by nuclear power plants. Nuclear power accounts for about 20% of electricity generated in the US. Nuclear is one of the most efficient fuel sources and could replace all fossil fuel power plants. However, there are significant problems with nuclear power plants. Currently there is no long-term facility in the world for the disposal of nuclear waste, a matter of significant concern. Also, some waste can be easily converted into nuclear weapons. As illustrated by Chernobyl, Three Mile Island, and Fukushima, human error can be very costly in terms of lives lost, environmental damage, and cost. Although no new nuclear power plant has been constructed in the US in over 20 years, several have recently been approved. Hydroelectricity is the cleanest of the major sources of energy and accounts for 7% of the electricity generated in the US. Hydropower uses the weight of water to turn turbines which generate electricity. The western US and Canada produce most of the hydro-electric power used in the US, but significant amounts are generated in the mountains of the east coast. Wind energy and solar power are renewable energy sources. Wind is one of the most popular forms of renewable energy; its use is expanding at an astounding rate. Both wind and solar energy depend on the vagaries of nature. The wind blows intermittently, and the sun can be used only during the day (and only when there are few clouds). However, there are places, such as Texas, Oklahoma, and Kansas, where the wind is reliable enough to generate significant amounts of energy. Although wind and solar account for only about 12% of electricity in the US, approximately 23% of electricity in Oklahoma comes from the wind. Renewable energy is limited by two factors: storage and availability. Unfortunately, electricity usage does not follow the same pattern as the sun or wind, requiring storage between generation and use. Both solar power and wind require a fair amount of land to build power plants. Although wind farms can be used for other purposes, such as agriculture, solar plants often cannot. Also, solar panels and wind turbines require earth materials, some of which are not easily extracted. So, although the wind and sun are free and environmentally clean, the hardware to convert them to electricity has an environmental cost that must be considered. In 2015 the US Department of Energy found that wind could provide 20% of US electricity by 2030 and 34% by 2050 (U.S. DOE (2015) Wind Vision Report.) Geothermal energy and tides are an insignificant part of the energy use in the US. In Iceland, however, geothermal energy (Iceland is on the mid-Atlantic ridge) is used to heat buildings and generate electricity. Because the energy source is free (like water) only the cost of the power plant is needed. Portugal is developing a project to use tidal currents to generate electricity. This project is in the development stage and is many years from realization. Both of these sources illustrate the work toward alternative energy sources to reduce our dependence on fossil fuels and the pollution they generate. The Energy Information Agency (http://eia.gov) is a good source of information on energy in the United States. 2. Discuss
source rock, trap, and reservoir rock—the three components necessary
for the occurrence of oil and gas underground. Oil and natural gas (petroleum) are the most important energy sources in the world today. Petroleum is extremely portable and can be used directly to run engines of many kinds. Burned, it produces heat, either for direct use or to be converted into other forms of energy such as electricity. The oil industry started in the US. Much oil is still produced in the US. In fact, the US is the world’s second producer of petroleum (behind Russia and ahead of Saudi Arabia). The Caspian Sea basin of the former Soviet Union is thought to contain as much oil as the Middle East and will be a significant source for the world supply once transportation is available. The US has enough oil and natural gas to be used for transportation for about the foreseeable future. Natural gas is the cleanest fossil fuel, producing only water and CO2. Oil ranges from very clean to high-sulfur and can produce significant amounts of pollutants. However, both are a source of CO2, the primary cause of anthropogenic climate change. Although most oil and gas are found in reservoirs underground and pumped to the surface, significant amounts can be found in oil shale and oil sands. The Athabasca oil sands are currently the only commercial oil sands operation in the world. Oil sands in the US and Canada contain more oil than current reserves in the Middle East. Unfortunately extracting the bitumen in oil sands is expensive and can be harmful to the environment. Three components are necessary for accumulations of oil and/or gas: a source rock, a reservoir rock, and a trap. A migration pathway is necessary for the petroleum to move from the source to the reservoir. The timing is also critical, as oil and gas must be formed then migrate into the reservoir after the trap forms. Source rocks are rich in organic material which, with appropriate amounts of heat and time, can be converted to oil or gas. Source rocks are usually (although not always) shales. Organic matter content as little as 2 or 3% by weight is sufficient to produce significant amounts of hydrocarbons. Once formed, oil and gas must migrate into a reservoir rock. The reservoir rock must be porous to hold the petroleum as it accumulates. In the same way a sponge holds water, a reservoir rock hold oil and gas in its pores, the spaces between the grains. Imaging a jar full of marbles. It still contains enough space among the individual marbles to be filled with water. A source rock and a reservoir are not sufficient to make an oil or gas field. The reservoir rock must be shaped into a form that holds the petroleum, the trap. A trap can be as simple as a dome, like an inverted bowl, or can be more complex in shape. As long as it has closure in all directions and can trap fluids (hydrocarbons) migrating upward it is a trap. Recent advances in exploration, horizontal drilling, and hydraulic fracturing have led to a large increase in oil and gas production in the US. These tight sands and shales often do not follow the classical source—migration—trap sequence stated above. Often the reservoir is also the source. Regardless of the geometry of the reservoir, the US is on its way to becoming, once again, the world’s largest producer of oil and gas, possibly as early as 2020. 3. Explain how each of the following
items is used in subsurface exploration to locate oil or gas: reflection seismic, electric well
logs, stratigraphic correlation, offshore platform, geologic map, subsurface
structure map, subsurface isopach map, and core samples and cutting samples. Reflection seismic is, essentially, sending sound waves into the ground, recording the returning energy (“echoes”) and interpreting the results. The results give a 2D or 3D picture of the subsurface in enough detail to determine structure and, often, stratigraphy. Lithology is extremely difficult to deduce from seismic alone. Once lithology is determined by well logs, however, seismic is an excellent tool to correlate between wells. Velocities are a critical property in determining the effectiveness of seismic. Electric well logs are geophysical measurements made in a well after it is drilled. Logs measure hole size quite accurately. Other logs are used to determine lithology and the presence of oil and gas with varying amounts of success, depending on the log used, the condition of the hole, and on the physical properties of the rocks surveyed. Cuttings are always generated when wells are drilled. As the bit grinds through the rock, it generates chips (cuttings) which are brought to the surface by the drilling mud. These cuttings allow a geologist to directly view the rocks the drill is penetrating, thus determining exact lithology. Although the lithology can easily be determined, the depth is only approximate. When a well penetrates a zone of particular interest, the geologist may request a core sample. Core is a round section of the rock taken inside the drilling pipe and brought to the surface for detailed examination. Unlike cuttings, the exact depth of a core sample is known. Core samples are large enough to perform laboratory tests such as for porosity and permeability, which cannot be done on cutting (they are too small). Correlation, connecting rock units from well to well or across a portion of the subsurface allows the geoscientist to interpret the geology of an area where there may be no direct data, or incomplete data. Correlation requires interpretation between wells to determine the depth, disappearance, and appearance of rock units or sub-units. Seismic, particularly 3D seismic, is an invaluable tool for correlation between (or among) known points, particularly wells. A geologic map is a graphic representation of the rocks exposed at the surface. Historically surface highs were drilled to find oil. Modern surface geological maps are of far less use in exploration than previously. Subsurface geologic maps, however, such as structural maps and isopach maps, are extremely useful. Subsurface maps are graphic displays of information about subsurface rocks or other items of interest to the geoscientist. In the same way topographic maps show elevation, the contours of a structural maps give the depth to the surface of a formation of interest. The contours of an isopach map show lines of equal thickness. Much exploration is now performed offshore. And offshore platform is a stable base from which to drill wells, produce oil and gas, and perform the myriad other tasks needed for successful exploration and production. Now oil field is discovered until the first successful well is drilled. In the ocean this may be from a drillship or floating platform. Once a field is discovered, a permanent platform is installed and more wells drilled both to produce the oil and gas and to determine the extent of the field. 4. Using
at least 20 data points provided by your counselor, create a subsurface
structure map and use it to explain how subsurface geology maps are used to
find oil, gas, or coal resources. (Note: Data points and instructions for
contouring can be found at http://www.geologymeritbadge.org , an answer is at the end of this
document.) Contour maps show lines of common value to indicate a surface. The common values may be elevation (topographic map), air pressure (weather isobar map), thickness (isopach map), or depth to the top of a horizon (subsurface structure map). A subsurface structure map is nothing more than a topographic map of a horizon or formation boundary in the subsurface. To construct a contour map, annotate each depth at the appropriate x- and y-coordinate. Select an appropriate contour interval based on your data. Select one level and interpolate its location between each pair of points. Remember, any individual contour may not appear between any give pair of points. Plot the points for each contour level. Draw a smooth line connecting all points of the same value. Remember that contours are generally parallel to each other unless there is evidence to the contrary and cannot cross. 5. Do
ONE of the following activities: a. Make
a tabletop display showing how oil and gas or coal is found, extracted, and
processed. You may use maps, books, articles from periodicals, and research
found on the Internet (with your parent’s permission). Share the
display with your counselor or a small group (such as your class at school)
in a five-minute presentation. b. With
your parent’s and counselor’s permission and assistance, arrange
for a visit to an operating drilling rig. While there, talk with a geologist
and ask to see what the geologist does onsite. Ask to see cutting samples
taken at the site. A tabletop display is best done as a poster such as used for science fairs. Use pictures, diagrams and words to explain the exploration, development, and production of petroleum or coal. PowerPoint slide shows are available on the SEG, AAPG, and GSA websites (see reference list). It is often difficult to get permission to visit a drilling rig. Remember that a rig can be dangerous—comply with all safety procedures. Remember to thank the geologist for his time. It is also good to thank his boss! A mailed, handwritten thankyou is always appreciated. 5c. Mineral Resources Option 1. Define “rock.”
Discuss the three classes of rocks including their origin and
characteristics.
A rock is a naturally occurring, solid substance composed of one mineral or a mixture of minerals that form an essential part of Earth's crust. Most rocks are inorganic but may contain significant amounts of organic matter. Coal and some limestones are the only rocks derived mostly or entirely from organic matter. There are three general types of rocks, sedimentary, igneous, and metamorphic, which may be further classified in groups. Sedimentary rocks are formed by the action of water, wind, or ice. About 75% of sedimentary rocks are clastic or detrital in origin. These rocks are composed of the fragments of previous rocks which have been eroded, transported, and deposited in a new location. Clastic rocks are mostly sandstone and shale (and their variations). Carbonates, which comprise almost 25% of sedimentary rocks, are composed primarily of calcium carbonate (calcite/aragonite -> limestone) or calcium-magnesium carbonate (dolomite -> dolostone). Most carbonates started as lime mud, composed of carbonate particles precipitated by organisms. These organisms range from the tiniest algae, to large organisms such as oysters, clams, and corals. Some carbonates are made entirely of shell fragments (coquina), tiny shells (chalk), or carbonate "BB's" (ooids). Evaporites, such as salt and gypsum (and anhydrite), make up a tiny fraction of sedimentary rocks, but can be economically very important. Salt, for example, can be found on any dinner table in the country, and much of it comes from salt mines. Gypsum is used to make sheet rock, used in constructing houses. Evaporites are formed by direct precipitation from sea water, and can form very thick layers. Evaporites are called chemical rocks. Igneous rocks are formed by the cooling and solidification of molten rock material (magma or lava). When the Earth began to cool, igneous rocks were the first formed, making them the oldest rocks on Earth. The oldest known igneous rock is 4.5 billion (4.5 ´ 109) years old, indicating that the Earth is at least that old. The youngest rocks on Earth are also igneous, and form from volcanic eruptions in Hawaii, Iceland, along the mid-ocean ridges, and at many other spots around the world. For example, Kilauea has been forming new rock on the island of Hawaii continuously since 1982. Igneous rocks can be either intrusive or extrusive. Extrusive rocks form as lava (magma at the surface) flows from the mouths (vents) of volcanoes, or from cracks in their sides, called fissures or is blown out of vents as ash, or pyroclastic (literally, thrown from the fire) material. Pumice (used in lava soap), scoria, and tuff are extrusive. Extrusive rocks are generally fine-grained or glassy in texture, although, especially if crystals have begun to form before extrusion, they may be porphyritic. Porphyritic rocks are fine-grained or glassy with embedded phenocrysts (larger crystals). Intrusive rocks are formed under the surface, when magma flows into cracks in existing rocks, between layers of rocks, or makes caverns in rocks (by melting or cracking the rocks). Because they cooled slower than extrusive rocks, intrusive rocks are generally courser-grained in texture. Intrusive rocks may also be porphyritic. Granite is a common intrusive rock. Metamorphic rocks are formed when pre-existing rocks are altered by heat and/or pressure. Although minor changes are common in rocks, the term metamorphic is reserved for those whose original structure has been destroyed, or whose mineral composition or character has been significantly altered. The distinction between high-end metamorphism (not quite melted) and low-end igneous (just barely melted) can be very hard to determine. Most metamorphic rocks studied by geologists start as sedimentary rocks. Because igneous rocks form from molten material, often at high temperatures and pressures, they are usually unaltered by processes that affect sedimentary rocks. Further, because of their nature, the early stages of metamorphism are often not readily detected in igneous rocks, and later stages may be indistinguishable from igneous rocks anyway. Some common metamorphic rocks are marble (meta-carbonates), slate (from shale), gneiss, and schist. 2. Define
“mineral.” Discuss the origin of minerals and their chemical
composition and identification properties, including hardness, specific
gravity, color, streak, cleavage, luster, and crystal form. A mineral is a naturally occurring, inorganic, homogeneous crystalline solid with a definite composition and structure. Each mineral has a distinctive set of physical and chemical properties. The important elements of the definition are: 1. Naturally occurring. Minerals occur in nature and are not created in a laboratory. Cubic zirconium, used as an inexpensive diamond substitute for jewelry, is not a mineral. Synthetic minerals, made in laboratories or factories, are often indistinguishable from natural minerals. As long as natural analogs exist, many mineralogists classify these synthetics as minerals, while others use a stricter definition. Care must be taken not to confuse a jeweler’s definition with the geologic definition, particularly when dealing with gems. For a jeweler, a cubic zirconium is a synthetic diamond; for a geologist it is an imitation. All diamonds, whether made in a laboratory or dug from the ground are natural to a jeweler; those made in a lab are synthetic to a geologist. 2. Inorganic. Minerals must not be formed by living organisms. Some rock-forming material, such as calcite, is originally formed organically. However, especially if they are partially recrystallized, they are considered minerals. (If they are completely recrystallized, they are no longer organically formed.) Bituminous coal is usually not considered a mineral (although it is a rock) due to its organic origin. Anthracite, metamorphic coal, usually is considered a mineral. 3. Homogeneous. While a single mineral must have the same composition throughout, many show zoning (bands of slightly different composition) or solid-solution (gradually changing composition) within a well-defined pair or group of end members. Because the compositions are well defined, and (generally) well understood, these are still minerals. 4. Crystalline. Minerals show a definite crystalline structure. That is, the atoms or molecules are arranged in a distinct pattern, which repeats throughout the mineral in all directions. A true glass, therefore, is not a mineral. 5. Solid. Minerals must be solid. Ice (solid) is a mineral, but water (liquid) is not. The only allowable exception is native mercury, which is liquid. 6. Definite composition. The composition of a given mineral is constant, or varies between two (or, sometimes among three) end members. The properties of the intermediate forms are not significantly different from those of the end members. Also, the intermediate members usually form regularly, with the pure end members often uncommon. Finally, trace impurities, which often determine the color to minerals but do not change other physical properties, are ignored. Six minerals form 96.5% of Earth's crust. Most rocks are composed of these in varying amounts. Any geologist who can identify these six minerals can identify most rocks. Calcite and dolomite, generally formed by organic processes, are also important in rock identification. The six most common minerals are: 1. Feldspars 64.0% 2. Quartz 18.0% 3. Amphibole 5.0% 4. Pyroxene 4.0% 5. Mica 4.0% 6. Olivine 1.5% Total 96.5% Identification of minerals is done using a hand lens, microscope, or higher technology (like a scanning electron microprobe). Some minerals are easily distinguished (halite, rock salt, tastes salty). Other minerals require laboratories to distinguish with certainty. Spinel, a relatively common mineral, is virtually indistinguishable from ruby, a gemstone, without proper instrumentation. Once such instruments became common, many ruby jewels were discovered to be spinel. Since then, spinel has become known as balas (false) ruby among jewelers. Some of the rubies in some of the crowns of European kings turned out to be spinel. Most common minerals, however, can be identified using their physical properties. Hardness, specific gravity (density), color and streak, luster, fracture and cleavage, and habit (crystal form and occurrence) are all important which, when taken together, give a very good indication of the mineral under consideration. By comparing a mineral’s physical properties with the ranges expected, as described in a book, even the inexperienced geologist or rock hound can identify most minerals. 3. Do
ONE of the following: a. Collect
10 different rocks or minerals. Record in a notebook where you obtained
(found, bought, traded) each one. Label each specimen, identify its class and
origin, determine its chemical composition, and list its physical properties.
Share your collection with your counselor. b. With
your counselor’s assistance, identify 15 different rocks and minerals.
List the name of each specimen, tell whether it is a rock or mineral, give
the name of its class (if it is a rock) or list its identifying physical
properties (if it is a mineral). Geologists collect related specimens to study the geology of a particular area. By identifying the rocks, fossils, or other materials geologists can determine the history of a particular region, the processes that have been active in the past or are active currently, and identify any features of scientific, economic, political or environmental interest. 4. List
three of the most common road-building materials used in your area. Explain
how each material is produced and how each is used in road building. Whether graveled, paved, or concrete, roads are built using Earth materials. Usually a bed of dirt, gravel, and/or crushed rock is laid down to smooth the ground and provide a base for the road. If the road is gravel, this base may be the entire road surface. Usually, however, the base is covered in pavement or cement. Pavement is essentially crushed rock (or large gravel) with tar to hold it together. Concrete requires sand, crushed rock (or large gravel), and cement (made from limestone). In all cases the specific materials used will depend on the local geology. In most portions of the mid-continent crushed limestone is used as aggregate. In mountainous regions of the Appalachians and the western US metamorphic rock may be used as limestone may be rare or absent. Sandstone, which crumbles relatively easily, is seldom used in road building. 5. Do
ONE of the following activities: a. With
your parent’s and counselor’s approval, visit an active mining
site, quarry, or sand and gravel pit. Tell your counselor what you learned
about the resources extracted from this location and how these resources are
used by society. b. With
your counselor, choose two examples of rocks and two examples of minerals.
Discuss the mining of these materials and describe how each is used by
society. c. With
your parent’s and counselor’s approval, visit the office of a
civil engineer and learn how geology is used in construction. Discuss what
you learned with your counselor. 5d. Earth History Option 1. Create
a chart showing suggested geological eras and periods. Determine which period
the rocks in your region were formed. Requirement 3 (above) describes how to read a geologic map to determine rock types and their ages. A time scale can be found at the end of this document. 2. Explain
to your counselor the processes of burial and fossilization, and discuss the
concept of extinction. Identify three plants or animals on the threatened or
endangered list of the U.S. Fish and Wildlife Service. Fossils are the remains of plants and animals preserved in rock. When an animal dies it may be buried. If burial occurs quickly, before the animal’s body is destroyed by other animals or surface processes, it may be preserved. As the sediment hardens around the animal it protects it. Eventually the animal becomes a part of the rock and is a fossil. Generally only the hard parts (bones, shells) are preserved, but soft parts can also be preserved in some cases. Many plants leave bark or leaf impressions in coal. Recently scientists found what they think is the preserved heart of a dinosaur. They did a CAT scan of a dinosaur skeleton, the rib cage still encased in rock, and found what looks like a heart inside. True fossils are the shells or bones themselves, preserved in rock. These are usually recrystallized or replaced with other minerals, making exact copies. These are not the original remains, but have the same outward shape and detail. Occasionally the shell will dissolve out and leave a hole in the rock. This “negative fossil” is called a mold (just like a mold in making plaster-of-Paris or clay objects). Finally, we have trace fossils. These are not direct fossils, but evidence of animals. Trace fossils include dinosaur tracks, worm burrows, and the like. Extinction occurs when an entire species disappears from Earth. This is a natural process that happens through time as species evolve and are replaced by others. Fossil evidence shows the extinction of innumerable species throughout geologic time, most replaced by others. Occasionally a mass extinction, the disappearance of many species at once, is seen. One well-known example is the extinction of dinosaurs at the end of the Cretaceous period about 65 million (65 ´ 106) years ago. There are many theories about this extinction; the most widely accepted is “nuclear” winter caused by a meteorite striking near the present Yucatan Peninsula in Mexico. Over the past 10,000 years or so the human race has led to the extinction of many species. Some species, such as the Passenger Pigeon, were hunted to extinction. Others were driven to extinction by loss of habitat and by careless use of land. Still others have been destroyed by changes to a fragile environment. More recently, people have worked to preserve species that are in danger. One of the most spectacular efforts involved the American Bald Eagle, which, while still protected, is no longer on the endangered species list. 3. Explain
to your counselor how fossils provide information about ancient life,
environment, climate, and geography. Discuss the following terms and explain
how animals from each habitat obtain food: Benthonic, pelagic, littoral, lacustrine,
open marine, brackish, fluvial, eolian, protected reef. Fossils can tell paleontologists a great deal about ancient life including environment, climate and geography. Fossil brachiopods and clams lived in shallow marine or lacustrine environments much as their modern counterparts. Fish, whether fossil or modern, live in water. The types of plants show whether the environment was hot or cold, wet or dry. Environments can be classified in many ways. Just as in the modern world, water in the geologic past was fresh, marine (the oceans) or brackish (a mix of marine and fresh water). Brackish water is usually found in swamps, lakes, and estuaries along the ocean shore. Fresh water is found on land in rivers, streams, and lakes. The marine environment is usually divided into the littoral, or near-shore environment, and the open marine environment away from shore. The boundary is usually defined as the approximate depth to which sunlight penetrates. The littoral environment includes many benthonic animals which live at the bottom of the ocean. The open marine environment includes many pelagic organisms and relatively few benthonic forms. Pelagic organisms generally float or swim near the surface of the ocean, although some may swim at great depths. A special case of the littoral environment is the protected reef. Reefs are living rock composed mostly of coral which protect a lagoon and shore from most of the wave action of the open sea. Some places on land, such as the Sahara Desert and the Arabian Peninsula are so dry that little vegetation exists to protect the surface. Wind often blows sand to form dunes and other features. These wind-blown sediments are eolian deposits. 4. Collect
10 different fossil plants or animals. Record in a notebook where you
obtained (found, bought, traded) each one. Classify each specimen to the best
of your ability, and explain how each one might have survived and obtained
food. Tell what else you can learn from these fossils. Fossils can tell a paleontologist much about the environment in which they lived, died, and were buried. To correlate this information to rocks, however, it is important to know where the fossils are found. The association of fossils, that is, which fossils are found together, can also be important. Fossils contain many clues. Aside from the environment they lived in, their burial location can often tell if they were transported after death, if the environment is changing, and how wide-spread a species is. All this helps the paleontologist diagnose the environment and conditions of a past time. 5. Do
ONE of the following: a. Visit
a science museum or the geology department of a local university that has
fossils on display. With your parent’s and counselor’s approval,
before you go, make an appointment with a curator or guide who can show you
how the fossils are preserved and prepared for display. b. Visit
a structure in your area that was built using fossiliferous rocks. Determine
what kind of rock was used and tell your counselor the kinds of fossil
evidence you found there. Many museums have docents who can answer questions. Most museums offer guided tours to groups of Scouts or a class or club. Many colleges and university geology departments have cabinets with fossils and rocks. One of the faculty members or graduate students is usually happy to give a brief guided tour. Again, a small group of Scouts may elicit a better reception than an individual Scout. Often they will show you the parts of the collection that are not on display. Remember to call first to make an appointment. Also, remember that we are Scouts. Be polite, attentive, and don’t touch unless explicitly permitted. Finally remember to say “Thank you!”—a hand-written note is really appreciated! Geologic Time Scale
From: GSA at https://www.geosociety.org/documents/gsa/timescale/timescl.pdf This website is NOT affiliated with or sponsored by the Boys Scouts of America. Any questions should be addressed to webmaster@geologymeritbadge.com. |