Geology Merit Badge – Geology is the science of the movements and physical history of the earth, the rocks, and minerals of which it is composed. The word comes from the Greek geo, meaning earth or land, and logos, meaning speech or story.
The modern study of geology started more than 200 years ago, when James Hutton published Theory of the Earth, claiming that studying the present is the key to unlocking the mysteries of the past.
This principle of uniformitarianism states that physical processes at work today on Earth, like wind and water erosion, have always been active and are responsible for all the features seen on Earth today, including remnants from the distant past.
Geology includes the study of materials that make up Earth, the processes that change it, and the history of how things happened, including human civilization, which depends on natural materials for existence.
- Geology Merit Badge Requirements
- Earth Down Under
- A Geologist’s Tools
- Streams Carving Earth’s Surface
Geology Merit Badge Requirements
- Define geology. Discuss how geologists learn about rock formations. In geology, explain why the study of the present is important to understanding the past.
- 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.
- Review a geologic map of your area or an area selected by your counselor, and discuss the different rock types and estimated ages of rocks represented. Determine whether the rocks are horizontal, folded, or faulted, and explain how you arrived at your conclusion.
- Do ONE of the following:
- 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.
- Find out about three career opportunities available in geology. Pick one and find out the education, training, and experience required for this profession. Discuss this with your counselor, and explain why this profession might interest you.
- Do ONE of the following:
- Surface and Sedimentary Processes Option
- 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.
- 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.
- 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.
- 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.
- 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.
- Energy Resources Option
- List the top five Earth resources used to generate electricity in the United States.
- Discuss source rock, trap, and reservoir rock the three components necessary for the occurrence of oil and gas underground.
- Explain how each of the following items is used in subsurface exploration to locate oil or gas: reflection seismic, electric good logs, stratigraphic correlation, offshore platform, geologic map, subsurface structure map, subsurface isopach map, and core samples and cutting samples.
- 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.
- Do ONE of the following activities:
- Make a display or presentation 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.
- 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.
- Mineral Resources Option
- Define rock. Discuss the three classes of rocks including their origin and characteristics.
- 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.
- Do ONE of the following:
- 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.
- 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, and give the name of its class (if it is a rock) or list its identifying physical properties (if it is a mineral).
- 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.
- Do ONE of the following activities:
- 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.
- 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.
- 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.
- Earth History Option
- Create a chart showing suggested geological eras and periods. Determine which period the rocks in your region might have been formed.
- Explain the theory of plate tectonics.
- Explain to your counselor the processes of burial and fossilization, and discuss the concept of extinction.
- 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.
- Collect 10 different fossil plants or animals OR (with your counselor’s assistance) to identify 15 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.
- Do ONE of the following:
- 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.
- 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.
- Visit a rock outcrop that contains fossils. Determine what kind of rock contains the fossils, and tell your counselor the kinds of fossil evidence you found at the outcrop.
- Prepare a display or presentation on your state fossil. Include an image of the fossil, the age of the fossil, and its classification. 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). If your state does not have a state fossil, you may select a state fossil from a neighboring state.
- Surface and Sedimentary Processes Option
Earth Down Under
Earth is a complicated system of land, sea, air, plants, and animals in constant change. Many branches of science must come together for geologists to understand what factors have shaped the land, including:
- Meteorology, the study of weather, to explain the work done by rain, streams, oceans, rivers, wind, ice, and frost.
- Geomorphology to study present-day hills and valleys and make educated guesses about landforms that no longer exist.
- Biology to learn about living plants and animals and their environments.
- Paleontology to unlock the secrets that fossils and other evidence tell about the past.
- Chemistry and physics to understand the formation and composition of rocks, minerals, ores, and petroleum.
A Geologist’s Tools
Simply put, geologists answer the question, “What’s down there?” They study everything that lies below the surface of the ground, interpreting the story of Earth by studying its layers.
1.Geological and Topographic Maps
William Smith, an English civil engineer, developed the first geological map in the early 1800s, and the tool proved to be so important that it is still in use today.
Geological maps show where rocks and sediments of the same type and age exist on Earth’s surface. Each rock or soil type is represented by a different color or line pattern.
Rocks of different formation, but of the same age, commonly are represented by different shades of the same color.
Geological maps are important in showing the distribution of rocks of the same age and type.
For example, because different rock types have different characteristics and cause different construction problems, it is important for construction companies to know the type of bedrock before construction begins.
A geological map of the area where construction will take place will allow the construction company to plan accordingly.
Geologists create geological maps from information gathered from direct observation in the field, interpretations of aerial photographs, and satellite data.
In addition to helping locate faults and other surface information, direct field observations allow geologists to measure several surfaces and subsurface features, including:
- Attitude, or the direction the rocks tend to go.
- Strike, or the compass direction of the feature.
- Dip, or the angle that the structural surface makes with the ground surface; measured perpendicular to strike.
A geologist also needs a topographic overlay (or overprint) showing what is on “top” of the ground by indicating elevations with contour lines.
In the same way that the shape of contours on a topographic map indicate hills, valleys, and stream direction, much can be told about a sedimentary sequence by the shape of its surface expressions, or outcrops.
For instance, curved outcrops often indicate folds, or areas where the rock beds were bent under intense pressure into a series of folded layers, like modeling clay.
2. Principles of Geology
Geologists have found that rock and land formations tend to follow certain patterns. This information may be able to assist you in answering the requirements of the No. 1 geology merit badge.
By applying the principles of superposition, stratigraphy, and structural geology, they can make better-educated guesses on the age, formation, and changes underneath the Earth’s surface.
As rock grains drop out of suspension in water, either from a stream or from an ocean current, they generally are deposited in layers, much like a layer cake: The bottom layer must be put on the plate first, followed by the layers above it.
In the same way, each layer of sand or mud is covered by another layer, and so on. The law of superposition states that younger layers are on top of older layers.
Younger layers may be removed or eroded by streams or rivers, and then even younger layers may be added on top. Sometimes rocks show a break in the sequence of the layers. These unconformities can be caused by erosion or pressure.
Abrupt changes that cut across a series of rock layers generally indicate faults, or areas where the rock layers were broken and where the rocks on one side of the break move away from the rocks on the other side.
These three concepts superposition (younger layers on top), stratigraphy (how layers form), and structural geology (how layers change as in folding) combine to help geologists figure out what’s beneath Earth using information about Earth’s surface.
3. Other Tools of Geologist’s
Although geological maps are very important, they help a geologist read and interpret only what is on Earth’s surface. Geologists have many other tools and sources of information. An example is well information.
You might think of wells as pipes that bring water or petroleum to the surface, but they also can give us much information about Earth’s subsurface, including information about the sequence of beds and structural features many thousands of feet below the surface.
Measurements made in wells, using electrical graphs, or well logs, and actual rock samples like cores and cuttings retrieved during drilling, precisely show the rocks in that location.
One of the most common tools in the oil industry is reflection seismology, in which sound waves are sent into Earth to measure the reflections, or echoes, to the tops of various rock layers.
Seismic reflections give an indirect measure of subsurface rocks and give geologists clues as to what lies under the Earth’s surface.
Streams Carving Earth’s Surface
Geologists study rocks to learn the history of their formation. Rivers and streams carry small pieces of rock, called sediment, in their current, and those pieces settle when the current loses its energy.
1. Sedimentary Rock
Sedimentary (sed-uh-MEN-tar-ee) rock is formed from pieces of weathered or broken down rocks that are carried and deposited by forces like water, wind, or glaciers and then compressed in layers.
Understanding where the rock grains come from and how they become sorted into layers in their present location and thickness can lead geologists to water, oil, and natural gas.
Sedimentary geologists study how moving water erodes rock grains from their original position, sorts them by size, and redeposits them into their new location. After deposition in this new location, other processes cement the grains together into rock units.
Because round grains do not fit perfectly together when packed into volume, there are spaces between the grains (pores) where water, oil, natural gas, or other fluids can collect.
The new rock is like a giant sponge. Although it looks solid, it can hold a lot of fluid in its pores.
2. Sediments in Suspension
The force of water current provides the energy to hold particles of dirt and rock in suspension, from the point where they wash into the stream until they settle to the bottom.
The amount of stream energy determines how big a grain can be transported. Bigger grains require more energy or faster streamflow.
Steam energy also determines where the grain is dropped, or deposited. When a steam slows down, it loses energy, and the bigger or heavier grains are dropped.
The shape of a stream’s path, or its morphology, affects the stream energy. Every winding stream has places where the current is faster or slower.
Geologists study the pattern of fluid flow to help determine the flow pattern in ancient streams now represented by rock formations.
The following information can help in answering the fifth requirement of the geology merit badge.
3. Stream Gradient
A stream’s energy is determined by the speed of the water flow. Streams have higher overall energy in the sections with a steeper gradient or downhill slope.
Water rushing from a higher elevation to lower elevation is never stopped, but it can be slowed down by local rock formations or by traps and dams.
Remember that fast-moving water transports larger and heavier grains while slower-moving water begins to drop the larger and heavier grains.
One way to estimate how fast water will flow is to calculate the stream gradient, or the ratio of vertical versus horizontal distance, in equal units.
In other words, if the elevation of a stream drops 10 feet for every 100 feet that it flows, you say that the gradient is 10 to 100 (or 1 to 10). A stream with this high gradient will have a great deal of energy in its water flow.
A slow stream might be one that flows 10 miles (or 52,800 feet) for every drop of 10 feet. In this case, the ratio will be 10 feet to 52,800 feet (or 1 to 5,280). This would be a low gradient representing low energy and a slow-moving stream.
4. Stream Patterns
The shape of a stream channel, or shape of the stream flow, also can determine the strength of a stream’s energy.
A geologist can predict the range of stream gradient and stream energy by looking at a map or an aerial photograph.
a. Straight Streams
When a stream flows in a channel without significant bends, geologists say it flows straight. Most commonly a straight stream is one that has so much energy and flows so fast that it manages to erode its own channel regardless of rock type.
Straight streams tend to have steep sides and the most energy. They can push large rocks and even boulders downhill.
Straight streams demonstrate the fastest stream velocity and usually indicate that the stream is dropping fast from a higher elevation to a lower elevation.
The stream shows you the direction of the downhill slope even if you do not have a topographic map.
b. Meandering Streams
Meandering streams are those that seem to twist and turn in a snakelike pattern. Geologists tend to find them in wide, flat areas. When a stream gradient is low, the stream slows down.
Then external factors, like friction between the water and the bank or channel bottom, also can affect streamflow.
Meandering, curving streams occur where the water current is not strong enough to force its way directly to base level, but only plays back and forth across a (mostly) flat area.
Meandering streams are often close to a larger body of water (base level) like a
lake, ocean, or a larger river. In time, this action is exaggerated.
The slower zone in the stream begins to drop grains of sediment, which makes the channel shallower as it fills the channel bottom.
In a shallow channel, the water flow spreads across more areas and creates more friction, which slows the water even more, and so on.
Another cause for a stream to meander might be an obstacle in the channel; perhaps the stream flows to a large boulder or a different kind of rock formation and does not have the energy (stream energy) to move it out of the way or wash it downstream.
The low-energy stream will flow around it. Meandering streams tend to have the slowest flow and the lowest stream gradient (energy level).
c. Dendritic Streams
Streams that have a dendritic pattern, resembling the veins in a leaf, tend to be made up of both straight and meandering stream segments. This pattern is most common in areas of varying elevation as in hilly or mountainous terrains.
Water from one side of a ravine will run to the bottom and join with water from the other side of the ravine. The combined stream will flow down the valley until it joins another runoff stream from a neighboring valley.
Because water always runs downhill, the intersection of two streams makes a south-pointing arrow pattern on a map.
Dendritic streams occupy the middle ground between straight streams and meandering streams, where the stream is still dropping from high ground to low ground, but where the drop is not as steep. There is still enough energy to show a primary direction of flow.
d. Trellis Streams
Trellis stream patterns are not as common as other patterns. They display a stream pattern influenced entirely by the underlying rocks. In an area where the rocks have been folded or thrust-faulted, the surface rocks occur in a pattern of parallel ridges.
Water will flow along the valley between these ridges until it finds a gap that allows it to escape and flow down to the next level.
Although these streams don’t flow in a straight line, they flow in very straight segments and their valley walls probably are steep-sided.
Trellis streams may have very high energy and very fast water. The softer rocks, which erode more easily than others, erode from between the harder layers and leave behind ridges of higher ground.
These parallel ridges print their pattern into the stream pattern because the water always runs downhill through the eroded valleys and flows around the higher ridges.
Envision a lake as a very wide, slow part of a stream. A stream usually fills the lake at one end, and the overflow spills through a low spot somewhere on the edge of the lake, allowing the stream to continue its flow downhill. Lakes are quiet, still water.
The base level occurs where the stream gradient becomes zero and the stream drops all the remaining grains from suspension.
There usually is very little current associated with a lake unless storm water is flowing into the upper end, so the very finest grains can settle from suspension. The cloudiness you see in a lake is mostly due to algae and other lake life.
Common minerals include calcite, quartz, feldspar, mica, pyrite, and gypsum. Because these chemical elements combine to form minerals, geologists know that the most common minerals are those composed of the most common elements.
The most abundant elements in Earth’s crust are oxygen and silicon (about 74 percent of Earth’s crust), so it should be no surprise that the most abundant minerals are silicates compounds of oxygen and silicon.
These common minerals may be unfamiliar to you because many people are fascinated with the less common minerals,such as metallic, silvery gray, and cubic galena.
But identifying minerals is an important step in recognizing the potential economic value of a substance, or even in identifying rocks you find on vacation or in your own back yard.
Geologists did not have sophisticated electronic equipment when the first mineralogists were identifying minerals, so they developed a series of comparative scales to determine a mineral’s physical properties and then to identify the minerals.
A comparative scale compares a single property among specimens. For example, one kind of mineral may be a darker red than other red minerals in the same rock. So you suspect it is a different mineral from the others.
When you compare it to a rock color scale, you can see its color tone is between two values on the scale. Geologists record this scale value in their notes because later it might be important information.
Most minerals can be identified using a combination of two or three of the following eight physical properties: hardness, specific gravity, color, cleavage, fracture, luster, crystal form, and streak.
You can also read the complete mineral information in the following link.
You wouldn’t rub your sunglasses across concrete because you know the concrete is harder and will scratch them. In the same way, a mineral is said to be harder than another material if it can scratch, or cut into, it.
The hardness test is a scratching test. Scratch one mineral against another to determine if it will scratch the other. Harder minerals will scratch softer ones.
Mineralogists have determined a numerical scale, based on the relative hardness of common minerals. This is called the Mohs’ scale.
|Mineral||Scale of Hardness||Common Use of Mineral||Common Materials With Similar Hardness|
|Gypsum||2||Plaster of parts||Fingernail 2.5|
|Calcite||3||Cement||Copper penny (pre-1973) 3.5|
|Fluorite||4||Fluoride in tootpaste|
|Apaite||5||Fertilizer||Steel nail 5|
|Orthoclase||6||Artificial teeth||Knife blade 5.5|
|Quartz||7||Quartz watch, Quartz sand in porcelain||Glass 6 to 7, Streak plate 6.5 to 7, Hardened steel file 7+|
|Corundurn (ruby, sapphire)||9||Ruby or sapphire for jewelry or lasers|
|Diamond||10||Jewelry and cutting tools|
2. Specific Gravity
Specific gravity is the weight of a substance compared with the weight of an equal amount of water. A heavy material like lead will have a high specific gravity. A lighter material like aluminum has a lower specific gravity.
A geologist uses this relative weight to quickly sort through a collection of minerals, placing heavier ones in one category and lighter ones in another.
Minerals all have a color, and the color is possibly the most common yet least reliable mineral test. Minerals can have impurities, or elements not normally in its crystal structure, that change its color appearance.
The purple amethyst is actually a milky or clear quartz crystal with traces of lithium.
Because the color can be misleading, geologists use color as a first-pass comparison before performing other tests.
4. Fracture and Cleavage
A mineral is said to fracture if, when struck against a hard object, the mineral breaks with uneven, or irregular, surfaces. Some different types of fractures are hackly, uneven, and conchoidal.
A mineral is said to cleave if it breaks along smooth surfaces and in regular directions. Minerals that chemically bond to form layers will cleave when broken apart, leaving smoother surfaces.
Cleavage can be a definite indicator of mineral identification. Fracture is the apparent lack of cleavage, and that information also is a definite indicator.
Luster refers to the appearance of the mineral in normal light. Minerals that look like glass are said to have a glassy luster.
Minerals with a dull, dirty appearance are said to have an earthy luster. Minerals also can appear waxy, oily, silky, or metallic.
6. Crystal Form
When a mineral solution is allowed to cool slowly, crystals can grow. A mineral takes a crystal form if it is allowed to grow without constraint, but the lack of a crystal shape does not rule out any particular mineral.
Geologists can identify certain minerals by their characteristic crystal shape.
For example, quartz may form in a volcanic steam vent, where the quartz is deposited one molecule at a time on the sides of the vent opening, allowing time for the quartz to form into crystals.
Granite forming underground contains quartz, but this quartz is crowded by other minerals and does not form larger crystals.
Streak is the powdery residue left when a mineral is dragged across a piece of rough porcelain. Such a piece of porcelain, which has a hardness of about 7, is called a streak plate and is carried in the field or used in the lab.
Sometimes a mineral’s streak is surprising because its color is different from the rock color. For example, the iron mineral limonite is yellow, but its streak is dark brown, typical of any iron mineral.