Geology Merit Badge

 

1. Explain what geology means.

 

In simple terms, geology is the study of the earth. It comes from the Greek geo or earth/land and logos, which means speech or story of. Geology can be applied to numerous applications in geography and planning, engineering, biology, physics, and chemistry. Like any science, the field of geology can be focused into major categories of interest, such as paleontology which study fossils, environmental geology which looks at how the geologic processes affects people. In school, geology usually means studying different rocks and minerals and how they formed. These rocks can hold clues about how the earth formed and how it looked millions of years ago. Historical geologists piece together earth’s history through the small rock record that still exists on earth’s surface. Exciting topics in geology may include volcanoes, earthquakes, and landslides and there are geologists who focus on how to predict and/or help people better prepare for them by studying them very closely.

 

3. Define rock. Discuss and define three classes of rocks. List the characteristics of each class, how they are formed, and how they are named.

 

Rock: A naturally occurring combination of minerals or of other pre-existing fragments. They are inorganic, or non-living, but could have come from once living organisms. Rocks can be hard or soft, many different colors, and exist just about anywhere on earth.

 

Igneous Rocks: These are rocks that crystallize from molten material at the surface of the earth (volcanic) or deep within the earth (Plutonic). Igneous rocks usually contain two or more minerals and the type of magma/lava the rock forms from determines what minerals will reside in the rock. Plutonic Igneous rocks have visible crystals in them and traveled great distances from the deep to be exposed at earth’s surface. Volcanic rocks cooled to quickly to allow crystals to grow; therefore volcanic rocks have very fine grains in them. Igneous rocks are named based on the mineral content of the rock. For example, Granite (a Plutonic rock) always has Potassium Rich Feldspar (K-spar), Plagioclase, and Quartz in it. The rock may contain other accessory minerals, or secondary minerals that may form out of the rock forming process.

 

Sedimentary Rocks: Are fragments of pre-existing rocks deposited in layers from water, ice, or air and then lithified, (or compacted, cemented, and crystallized) into solid rock. Sedimentary rocks will usually have a layered look to them or have sedimentary structures on them, which can aid in identifying what kind of environment these rocks were deposited in. An obvious sedimentary structure includes fossils. There are different size clasts, or rock fragments in each type of sedimentary rock. Gravel-sized clasts will form Conglomerate, sand-sized clasts will form sandstone, silt-sized clasts will form siltstone, and clay-sized clasts will form shale or claystone. Limestone is another sedimentary rock that can form from a number of different methods. Putting acid on its surface can identify this rock since the acid will react with the Calcium Carbonate (CaCO3) in the rock and fizz.

 

Metamorphic Rocks: Preexisting rocks that have been altered by heat and/or pressure. These rocks are usually formed deep beneath earth’s surface or in mountain building events. A common metamorphic structure is foliation, which is a wavy structure that results when minerals grow/recrystallize flat during metamorphism. This feature often makes metamorphic rocks look wavy or folded. Still other metamorphic rocks look massive but if you look closely, the minerals of these rocks will look fused like they were pushed together. Marble will have a massive appearance with some impurities in the rock giving it wavy colors. These rocks can be named by either their foliation or by their mineral content. Gneiss is a common foliated rock that has alternating bands of light and dark minerals.

 

4. Define mineral. Tell how to identify minerals. Tell how rocks and minerals differ. List five of the most common rock forming minerals. Tell how they are identified. Tell how hardness, specific gravity, color, streak, cleavage, luster, and crystal form are useful in identifying minerals.

 

Mineral: A naturally occurring crystalline substance with well-defined physical properties and a definite range of chemical composition. They differ from rocks simply because rocks are usually made up of two or more minerals. But some rocks are a result of minerals breaking down due to weathering so some rocks may contain only one mineral.

 

Five most common rock-forming minerals:

Mineral

% In crust

Rock examples

Plagioclase Group

39

Many Igneous rocks

Quartz

12

Sandstones, Granite

Orthoclase Feldspar

12

Granites, Sandstones

Pyroxene Group

11

Dark Igneous rocks

Micas

5

All rocks, accessory mineral

Others:

Amphibole Group

5

Granites, Gneiss

Clay minerals

5

Shales, slates

Olivine

3

Basalt, Dark Igneous rocks

Calcium Carbonate

?

Limestone

Gypsum

<1

 

 

The identification of minerals can be done one of two ways. There are simple field techniques that geologists employ on a daily basis when doing field research. Also, a geologist can take samples back to their laboratory to run more complex tests on the sample to identify it further. A mass spectrometer or X-ray diffraction machines are two examples of laboratory means of identification. Most geologists tend to use field methods to simply id a mineral.

 

Hardness: Measures how difficult a mineral can be to scratch. The Moh’s hardness scale classifies hardness on a scale of 1 to 10 with one being the most soft and 10 being the hardest:

 

Hardness

Mineral

What will scratch it?

1

Talc

Fingernail

2

Gypsum

Fingernail

3

Calcite

Penny

4

Fluorite

Knife Blade

5

Apatite

Glass

6

Orthoclase

Steel File (Non-stainless)

7

Quartz

Corundum

8

Topaz

Corundum

9

Corundum

Diamond

10

Diamond

---

This is always a good property to test. Check a field guide in rocks and minerals for the hardness of other minerals.

 

Specific Gravity: or more commonly know as density. It is measured by testing its mass against how much an equal amount of water it will displace. Heavy minerals have a high density (like Galena) and light minerals have a low density (like Calcite)

 

Color: A very easy, yet sometimes misleading property. Some minerals (like Native Sulfur) will always have a distinct color (Yellow). Other minerals may have many different colors depending on many factors (Quartz is a good example).

 

Streak: This is the color of a mineral when it is powdered. In order to do this test you need a piece of porcelain tile (which only has a hardness of 6 so it wont work on anything above quartz). The mineral Sphalerite that is dark in color will always leave a distinct yellow streak.

 

Cleavage: Is a very important identifying feature. Cleavage is the ability of the mineral to break along even planes of weakness. Minerals can have one (Basal cleavage) or many planes of cleavage. Some common types are cubic (3 planes at 90 degrees) and rhombic cleavage (3 planes not at 90 degrees). Halite (Rock salt) and Galena are common minerals with cubic cleavage. Calcite has rhombic cleavage. Fluorite and Diamond have four cleavage planes, which gives them both a common octahedral crystal.

 

Luster: Is the mineral’s ability to reflect light. Many iron-bearing minerals have a metallic luster. Glassy and pearly lusters are other common types.

 

Crystal Form: Is different from cleavage since when you break a crystal form, the mineral will not display that form again. When you break along a cleavage plane, the mineral will take the form again. Quartz is an excellent example. Quartz has no cleavage but it does have a distinct crystalline form. Quartz crystals usually form 6-sided hexagonal prisms. But when you break these prisms, they do not form again.

 

6. Draw a diagram of the hydrologic cycle and discuss it and its effects with your counselor.

 

Click here for a picture of the hydrologic cycle.

 

7a. Tell about the occurrence of volcanoes on land and in the ocean. Describe the difference between intrusive and extrusive igneous rocks.

 

Volcanoes that occur on the land arise from two different plate settings. The first types are the volcanoes like Mount St. Helens or Mt. Rainier in the Cascade Mountains. These volcanoes formed from a process called subduction. Subduction is a part of the plate tectonic theory when the denser ocean crust plunges beneath continental crust. As the crust descends into the mantle, the rocks begin to melt and form magma. The magma is lighter than the surrounding rock and starts to rise up toward the surface. The magma builds and builds until it explosively erupts onto the surface of the earth. A composite volcano is formed. Sometimes the magma does not erupt at it cools beneath the surface of the earth. These volcanic eruptions are typically violent and can eject a vast amount of material into the earth’s atmosphere. It is believed that a large enough volcanic eruption can cause earth’s climate to change.

 

Another type of land volcano is known as a caldera. These sunken volcanoes usually form over a “hot spot” or an area in the earth’s mantle that is unusually active with magma. Yellowstone National Park sits over a hot spot and is a caldera volcano. A caldera eruption is much more violent than a composite volcano and can spread material over great distances. The last time Yellowstone caldera erupted (650,000 years ago) it spread ash 1 meter thick as far away as Nebraska!

 

Oceanic volcanoes occur either deep underwater on the bottom or can build up and form volcanic island chains like Hawaii. Underwater volcanoes also occur at plate boundaries like mid-ocean ridges. This is an area where the sea floor is spreading apart and forming new ocean crust. In the case of Hawaii, there is at hot spot again but this time the magma is erupting out over ocean crust. This builds up an enormous mountain from the sea floor. Mouna Loa is actually the largest mountain on earth, if you measure it from the bottom of the seafloor to the top. The lava that flows out from this volcano is gentle and rarely explosive.

 

Extrusive igneous rocks are the save as Volcanic. They are rocks that cool quickly and form small crystals. Basalt is a common extrusive rock and is found all over the place in Hawaii. An intrusive igneous rock is rock that form beneath earth’s crust and cool very slowly allowing the mineral crystals to form.

 

7b. Describe the major steps in the geologic history of a mountain range. Describe an anticline, syncline, fault, strike, dip, and an unconformity. Discuss the relationship between mountain building and erosion in forming the present landscape.

 

 (I will use the Appalachian Mountains as an example for this requirement)

 

In plate tectonics, a mountain building event or orogen can take millions of years. The Appalachians took over 250 million years to form and some argue they are still forming to this day. A mountain chain basically forms when two continental plates collide and numerous thrust faults occur throughout the mountain chain. The rocks of both continents become fused together and intense metamorphism occurs along that boundary. As you move away from the suture point, metamorphism is less severe and intense folding is seen. Southeastern Pennsylvania sits where the mountains were severely metamorphosed and the current Appalachians are where intense folding took place. After the collision, erosion begins to degrade the mountains. A process known as isostatic uplift however will continually lift the mountains upward. The same thing happens to an iceberg as it melts in the ocean. The volume of the iceberg above the sea will always remain relatively constant as it melts as long as there is ice below the sea to balance the ice mass out. Once the mountains are eroded down to the nub, a craton now exists and very little erosion takes place. This is also known as a stable platform.

 

Anticline: A generally convex-upward fold that has older rocks in its core.

 

Syncline: A generally concave-upward fold that contains younger rocks in its core.

 

Fault: A fracture in the earth along which there has been displacement (or movement relative to each other)

 

Strike: The direction, west or east of north of the trace of the inclined plane along a horizontal plane.

 

Dip: The angle and direction perpendicular to strike at which an inclined plane make with a horizontal plane.

 

Unconformity: An erosional time gap in the geologic record between sedimentary layers.

 

7c. Describe the major features of an ocean floor between the shoreline on either side.

 

Starting from the Jersey Shore, you walk off the beach onto the continental shelf. This is a gently sloping plain that is a part of the continental crust; it just happens to be covered by the ocean. Next you will arrive at the shelf break and begin a quick steep descent along the continental slope. This is where the continental crust stops and where the oceanic crust begins. You will soon start a gentler slope down as you arrive at the continental rise. This is where sediment falling down the slope has piled up and is starting to become rock. As you leave the rise, a flat, long featureless plain spreads out before you. This is the abyssal plain. Sediments have built up over the years accumulating up to several hundred feet thick. Occasionally you might run into a guyot, or an old volcano that was once above sea level and has been flattened by wave erosion. You might see a seamount, which is a volcano that never made it above sea level. Some hills are now starting to form these are the abyssal hills. These hills form from volcanic rocks that are covered by sediment. Now you start a climb back up along the ocean ridge. You have now reached the Mid-Atlantic ridge where the Atlantic Ocean gets bigger every year. You might see a fracture zone or the rift valley where the new ocean crust is forming. As you walk along the other half toward Portugal, you will start the whole process over again, but backwards!

 

(Another ocean feature that you wont see too frequently in the Atlantic but numerous times in the Pacific is a deep-sea trench. This is the area where ocean crust is plunging beneath a continental or other ocean crust)

 

8. The Geologic Time Scale

 

Era

Period

Epoch

Age Began (mya)

Cenozoic

Quaternary

Holocene or Recent

.01

Pleistocene

1.6

Tertiary

Pliocene

5.3

Miocene

23.7

Oligocene

36.6

Eocene

57.8

Paleocene

66

Mesozoic

Cretaceous

Many

144

Jurassic

Many

208

Triassic

Many

245

Paleozoic

Permian

Many

286

Pennsylvanian

Many

320

Mississippian

Many

360

Devonian

Many

408

Silurian

Many

438

Ordovician

Many

505

Cambrian

Many

570

Pre-Cambrian

--

--

4,500

 

9a. Tell what fossils are and how they aid in understanding the story of earth’s history.

 

Fossils are remains on an ancient organism preserved in the rock record. Fossils can be used to index different rock layers or strata over hundreds of miles (or between distant continents). Index fossils are common fossils seen in certain periods of time in the rock record. As life became more evolved, the fossils became more and more diverse and spread throughout the earth. Also, gaps or fossils no longer in the rock record show extinctions. These extinctions could explain a major event happening on earth like a volcanic eruption or meteor impact.

 

9c. Discuss with your counselor the theory of continental drift.

 

Alfred Wegener developed this theory in the early 20th century after studying maps of the world and he concluded that Africa, Europe, South and North America once fit together. He called this super continent Pangea. Other evidence for this included similar fossils found on the landmasses; researched uncovered by Alexander Du Toit in the 1930’s. Also, contiguous mountain chains when the continents are together (The Appalachians, Atlas, and Caledonian Mountains were all one mountain chain).  Since Wegener had no model to support his theory, it was rejected since no one believed that the continent could just drift apart. His theory gained some support after World War II when radar maps of the ocean floor revealed a long mountain chain down the center of the Atlantic. It was once thought that the ocean was featureless from coast to coast. Upon further investigation of this ridge, it was found to have a similar outline as the continents. But how did they move? Enter the idea of convection. Just like when you boil a pot of water, convection currents force warm water to rise and cool water to sink because of their densities. The same argument was made with molten rock. Hot magma rises at ocean ridges (or continental rift valleys) and cool rock sinks at subduction zones. This is the engine behind the theory on how the plates have migrated over time.

 

11a. Describe five energy sources, how they occur, and how they are used today. Describe the source of the products supplied by your local utilities. Tell which of these products are related to geologic processes.

 

The following are five forms of energy resources used in the United States that deal directly with geology. There are other sources also described that are considered alternatives. All of these products produce electrical power supplied to you by your local utility company.

 

Coal: Coal is a rock formed from non-decomposed plant materials that were buried millions of years ago. The plant material was deposited in an anoxic or and oxygen deprived environment. Because no oxygen was present, the plant material did not decompose and eventually turned into peat. As the peat was buried further, compaction occurred and the coal turned into lignite, which is also known as brown coal. Upon further burial, the lignite became further refined into bituminous coal. This coal is found in abundance in Western Pennsylvania and throughout Southeast Ohio, West Virginia, and Eastern Kentucky. If light metamorphism or severe folding is applied to bituminous coal, it turns into Anthracite coal. This is the highest grade of coal in terms of heat output. Pennsylvania has some of the world’s richest anthracite deposits. If anthracite coal is subjected to further metamorphism or deformation, it turns into graphite- not diamond, which is a common misconception.

          Coal was used a fuel for everything during 1880’s through the early twentieth century. There were even coal driven automobiles. People heated their homes with coal. Industry used it to move their machinery and utilities burned coal to power their generators. Coal has its drawbacks. It produces a lot of ash, and coal often times contains sulfides and sulfates in it. These sulfur compounds are released into the atmosphere as sulfur dioxide (SO2) and react with water vapor to form sulfuric acid (H2SO4). This can drastically reduce rainwater’s pH to dangerous levels and is the leading cause of acid rain.

 

Oil and Natural Gas: These two resources are commonly grouped together and called petroleum. They both form from the same process and are almost always found together. (Along with water) Ancient seas produced many small organisms, which died and settled to the bottom of the sea in an oxygen-deprived environment. As these small organisms were buried in mud, they became volatile, or most elements were driven off except for carbon (and of course, sulfur). However, instead of forming a hard material, the components became liquefied and began to migrate upwards since it was less dense. The liquid moved from a source rock into a reservoir rock, which is porous enough to hold the petroleum. A gas (methane, CH4) is a result of this decomposition and it escapes to the reservoir rock also. Finally, a cap rock that is impervious or will not allow these materials to migrate further is needed to contain the petroleum.

          Oil was first drilled for commercial use in Titusville Pennsylvania. It wasn’t until a waste product of distillation or refined oil was found to be a useful fuel in an internal combustion engine that oil’s worth became so valuable. Now petrochemicals are used in a wide range of products that include plastics, tars, medicines, and fertilizers. But it is fuel oils that humans primarily use it for. Natural Gas was usually vented or burned of at the site of oil wells until a method was developed for capturing this gas and using it to fuel power plants and people’s homes. Today, natural gas is the number one fuel for power plants since it is the cleanest fossil fuel (and the U.S. has plenty of reserves). Methane is also mined from coal beds and from old landfills.

 

Uranium: Is a radioactive heavy-element. It is found in many metamorphic and igneous rocks in the western United States. Uranium ore is mined from rock and then its put through a process called enrichment. Most Uranium ore contains the isotope U-238. This isotope cannot be used in controlled (or uncontrolled) nuclear reactions. The isotope U-235, which occurs in small amounts in Uranium ore, is needed for nuclear fuel rods. The enrichment process removed everything from the uranium ore except U-235. This is then manufactured into Uranium fuel rods, which are shipped to nuclear reactors for use for electrical power generation.

          Nuclear power was promised to bring “free energy to all Americans” in the 1950’s. However, people who made the statement vastly underestimated the amount of energy this country uses. Over 250 nuclear power plants would be needed in the East alone to meet our current demands. After the Three Mile Island scare, the public became suspicious and afraid of nuclear power. And since the Chernobyl nuclear accident in the Ukraine, the U.S. has not built or even order a new nuclear power plant to be built. The future of nuclear power is in doubt since it also produces highly radioactive waste and this country faces a problem of where to dispose of this waste safely.

 

Geothermal: This source of energy is one of the most promising in terms of electrical power generation and use in building climate control. Hot geysers in the earth’s surface heats water, which can be pumped up and used to spin turbines or to heat water to spin turbines. Northern California has numerous geothermal power plants to generate power. And that is its only drawback; it depends on where you live. The East coast has no active geothermal hotspots in which to draw this energy, but it does rely on another constant temperature to help in home/building heating.

          The temperature of the crust just below the surface is a constant 50 to 55 degrees Fahrenheit. Air from this depth can pumped up into a geothermal climate control device and allows a building’s air to be heated or cooled to that temperature. Depending on the season, the air can be heated, or released into the building, which can save hundreds to thousands of dollars a month on heating or air conditioning bills.

 

Hydropower: One of the oldest sources of energy known to man, it was used to power mills and other paddle-wheel plants for thousands of years. It was not until the onset of large-scale dams that hydropower became an important for electrical power generation. These dams had to be placed in geological ideal areas in order to prevent a catastrophic failure. These dams also serve the purpose of flood-control, water reservoirs, and recreation. Over half of the rivers in the United States ideal for hydropower have been developed.

          Hydropower is not considered a green source of energy anymore by major groups since the ecological damage they cause outweigh the good for society. Large reservoirs cause high amounts of evaporation that lowers the potential usable water for a given reservoir. Barricades to fish migration and other water migrations occur. The flooding of the river valley also displaces a large number of wildlife and shrinks the usable habitat for many species of animals. But hydropower is considered an excellent alternative to coal, gas, and nuclear power since it causes little to no pollution.

 

Wind: This is another power source that was used by Europeans to power gristmills (windmills). And wind is becoming a viable energy source in the years to come. Wind mill “farms” are being placed in geographically ideal locations where the winds are constantly (or a least a majority of the time) blowing at 10 km/hr. These areas are usually at mount gaps or along vast flat plains where the wind has very little interruption from hills or trees. Wind is even being harnessed in the canyons of skyscrapers in large cities. The plans for the 1776 ft. tower on the World Trade Center site calls for wind turbines to be in the top 1/3 of the spire to help generate some electricity for use in the surrounding buildings.

 

Solar: It is a dream of man to harness the power of the sun like plants do naturally for us. Many of use passive solar power techniques in our homes to help save on our energy bills. But photovoltaic cells are becoming more commonplace for en situ, or on site electrical power generation. The roofs are some buildings are being installed with these cells and areas of the country that receive vast quanities of sunlight throughout the year have these power plants already installed.

 

Biomass: This term is a “lump” term that includes everything from wood to garbage as a fuel. Wood is burned in fireplaces in this country and is the main cooking fuel in others. Garbage is burned and converted to electrical power in this country to save landfill space. Hydrogen fuel cells are still in their infancy and still need more research to see if they can be used on a large scale. Ethanol, or corn/soy-based fuel, is also becoming a fuel alternative. Already used by many instead of diesel fuel, ethanol burns cleaner than gas and come from a renewable plant resource. Ethanol is also being added to regular gasoline to conserve reserves. Ethanol however, does have its drawbacks. It can produce formaldehyde, a carcinogen. Also, its production cannot match the current production of gasoline in order to replace it.

 

The only way to achieve a sound energy plan is balance and conservation. Using fossil fuel resources at our current consumption rates would put us out of these resources in a matter of 75 years. By starting to use alternative fuels now, fossil fuels are conserved for another day. Also, using alternative fuels such ethanol or hydrogen for moving an automobile would save vital petrochemicals for use in making plastics and medicines. Just imagine a modern hospital without plastic!