GOL 106 Study Guide for Exam 1

The following are questions important to gaining an overall understanding of the material for Exam I. The Exam format will be much like the Module and Lab quizzes. Reviewing those will be important for success on the exam. Module 1 - Earth as a System 1. Where does the energy to drive the Earth System come from? This includes the energy to drive Earth’s internal and external spheres. Earth’s interior heat and the sun. 2. Why is Earth’s interior still hot? Where does the heat come from? Radioactive decay of unstable elements within our planet’s interior produces a great deal of heat energy. Another heat source comes from remnant primordial heat still yet to dissipate from the planet’s formation. Finally, frictional heating plays a role, descending material rubs against other materials. 3. Briefly explain each of Earth’s spheres a. Exosphere: Space, the sun powers our solar system. b. Atmosphere; where does the energy come from that drives this sphere? gaseous environment c. Hydrosphere; where does the energy come from that drives this sphere? liquid environment, powered by the sun d. Cryosphere icy environment e. Biosphere; where does the energy come from that drives this sphere? Living environment, the sun? f. Lithosphere/geosphere; where does the energy come from that drives this sphere? solid environment g. Anthroposphere: Human environment 4. Follow natural or manmade forcing events through the Earth System identifying direct and indirect effects. (Examples of forcing events can be found in the Earth Systems Chapter text ). Earthquake Lithosphere/Geosphere: Direct – local to regional changes in landscape near fault. Hydrosphere: Indirect via Geosphere – Possible tsunamis or coastal landslides and turbidity currents Atmosphere: Indirect via Geosphere – release of dust, debris, and toxic gases in some instances Biosphere: direct and indirect – depending on the species, building collapse and liquefaction can lead to death; ecosystem changes are possible 5. What are, and provide an example of … a. Forcings: These are things that force changes to the dynamic equilibrium at the time. A forcing event is an action that moves a system away from dynamic equilibrium, usually through an initial push within one system. Anthropogenic greenhouse emissions are a forcing that today is causing the global temperature to warm. This initial forcing, of course, leads to additional effects downstream. Forcing events never happen in isolation, there are always additional direct and indirect repercussions.

b. Feedbacks: Feedbacks are the results of forcings. No matter what the forcing event is, there are always feedbacks that occur as a result. Feedbacks can amplify the initial forcing (positive or amplifying feedback). They can also balance that forcing (negative or balancing feedback). Eventually, balancing feedbacks will work to bring a system to equilibrium once again. Amplifying feedbacks are not always going to happen, by contrast. Polar ice is reduced by warming, more dark-colored water is exposed. Seawater is much darker in color than ice. More energy is then absorbed by the water than was by the ice, further warming the water and melting even more ice. Less ice leads to an amplification of warming. c. Sinks: Within systems, energy and materials can be stored until it is moved from one part of a system to another. Locations within a system where this occurs are referred to as sinks. Every biogeochemical cycle has sinks. In the carbon cycle, carbon is stored for very long periods of time in the form of limestone or fossil fuels. On the shorter term, it is stored in ocean water, in plants, or in the atmosphere. d. Tipping points: Point of no return. A system moves so far out of its prior balance that, once it regains a sustainable equilibrium, it has a very different look and behavior than it did before. Initial forcings, followed by the actions of amplifying feedbacks can eventually cause a system to tip into an entirely new circumstance. An example would be an oil spill which transforms the marine ecosystem . In both these cases although the driving event may have been unexpected (and rare) the impact on the ecosystem is not. Module 2 - Earth Materials Minerals 1. What is the definition of a mineral? How does that differ from the definition of a rock? A mineral is a substance that is: 1) naturally occurring, 2) inorganic, 3) solid at room temperature, 4) has an orderly and repeating internal crystalline structure, and 5) a chemical composition that can be defined by a chemical formula. “A mineral is an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes.” A rock is a solid substance that is made of one or more minerals or mineraloids. 2. Review the Mineral Gallery with your Mineral Identification Chart. Be able to identify the Big Ten minerals based on the mineral characteristics (the chart would be provided on the exam). 3. What are the 8 most common elements of Earth’s crust? The most common elements in the crust are: oxygen O (46.6%), silicon Si (27.7%), aluminum Al (8.1%), iron Fe (5%), calcium Ca (3.6%), sodium Na (2.8%), potassium K (2.6%), magnesium Mg (2.1%). Only 1.5% of the crust is made of something other than these 8 elements. 4. Which two elements make up over 70% of the Earth’s crust? Oxygen and Silicon

4. R eview the lab exercises. Given the Igneous Rock Classification Diagram, be able to identify igneous rocks, their texture and their composition (which minerals would typically be present). The diagram will be provided. 5. Describe how and why the texture differs between plutonic and volcanic igneous rocks. The slow cooling process allows crystals to grow large, giving intrusive igneous rock a coarse-grained or phaneritic texture. The individual mineral crystals are readily visible to the unaided eye. When lava is extruded onto the surface, or intruded into shallow fissures near the surface and cools, the resulting igneous rock is called extrusive or volcanic. Extrusive igneous rocks have a fine-grained or aphanitic texture, in which the grains are too small to see with the unaided eye. The fine-grained texture indicates the quickly cooling lava did not have time to grow large crystals. 6. What is the main difference between the different compositions of igneous rocks (ultramafic, mafic, intermediate and felsic)? Differing amounts of silica, potassium, sodium, calcium, iron, and magnesium found in the minerals that make up the rocks. Mafic refers to the overall composition being high in concentrations of ma gnesium (Mg) and iron ( F e). The minerals that compose mafic rocks are referred to as the ferromagnesian minerals, meaning, enriched in Fe and Mg. Felsic refers to the overall composition being enriched in the fel dspar minerals of sodium-rich plagioclase and potassium feldspar plus si lica (SiO 2 ) in the form of quartz. 7. What conditions are necessary to produce igneous rocks? Metamorphic rocks? Magma can either cool slowly within the crust (over centuries to millions of years)— forming intrusive igneous rock ( also called plutonic rock ), or erupt onto the surface and cool quickly (within seconds to years)—forming extrusive igneous rock ( also called volcanic rock ). Intrusive igneous rock typically crystallizes at depths of hundreds of meters to tens of kilometers below the surface. Any rock type that becomes buried deep within the crust is subjected to increasing heat and confining pressure. Tectonic forces of colliding plates can add additional stress to the buried rock. These changing conditions affect the stability of the pre-existing minerals and the fabric, or texture, of the original rock. This results in the formation of metamorphic rock. 8. How does a “foliated” texture develop in metamorphic rocks? Are all metamorphic rocks foliated? Why not? Foliated : formed in an environment subjected to differential stress resulting in a distinct alignment of minerals. Foliated metamorphic rocks are named based on the style of their foliations. Each rock name has a specific texture that defines and distinguishes it. Non-foliated : either not subjected to directed pressure or, the dominant mineral does not tend to display any alignment. There are two main types of metamorphic rocks: those that are foliated because they have formed in an environment with either directed pressure or shear stress, and those

that are not foliated because they have formed in an environment without directed pressure or relatively near the surface with very little pressure at all. 9. What is the difference between regional and contact metamorphism? Regional metamorphism . This occurs over a wide expanse of the crust, hundreds to more than a thousand kilometers across, resulting from the collision and compression of tectonic plates. Contact metamorphism is much simpler and affects pre-existing rock by baking them through contact with molten rock material either by intrusion of magma or extrusion of lava on the surface. Intrusion can occur very deep in the crust and involve large areas affected by heat associated with vast magma chambers. Intrusion can also be much smaller and take place closer to the surface or involve the baking of the surface rock through volcanic eruption of lava. 10. Which large scale tectonic environment will produce regional metamorphism? Convergent tectonic margins (where plates collide)? 11. Review the lab exercise. Given the Metamorphic Rock Identification Chart, be able to identify the common metamorphic rocks, their texture and their composition. The chart will be provided. Module 3 - Rocks (concentrating on sedimentary) 1. What are the 4 “agents” of weathering? water, wind, gravity, or ice 2. Define physical weathering and provide an example. Physical weathering is simply the process of physical disintegration: the breaking of solid rock into smaller pieces. The “agents” assist in this process which results in the exposure of an ever increasing number of surfaces to additional weathering. 3. Define chemical weathering and provide an example. Chemical weathering produces changes in the chemistry of minerals in the pre-existing rock. These changes may result in new mineral formation through the addition or subtraction of elements from the original mineral structure or, in the further disintegration of the pre-existing minerals by chemical decomposition. Some examples of chemical weathering are rust, which happens through oxidation and acid rain, caused from carbonic acid dissolves rocks . Other chemical weathering, such as dissolution, causes rocks and minerals to break down to form soil. 4. What are the differences in sediment and sedimentary rock classification? Meaning, the differences in clastic, chemical, biochemical and organic classification. Clastic sedimentary rocks are made of sediments. The sediments differ in size. Chemical sedimentary rocks are made of minerals that precipitate from saline water. Organic sedimentary rocks are made from the bodies of organisms. Sediments are classified by particle size, ranging from the finest clays (diameter <0.004 mm) to the largest boulders (> 256 mm )(Figure 12.1. 2). Among other things, grain size represents the conditions under which the sediment was deposited.

The main difference between carbonate and clastic reservoirs is that clastic deposition requires the transportation of grains to the sedimentary basin, whereas carbonates originate within the basin of deposition . d. Coal deposits would indicate what type of environment? Lush swamplands can create conditions conducive to coal formation. Shallow-water, organic material- rich marine sediment can become highly productive petroleum and natural gas deposits e. What is a facies? What is the lateral succession of facies? In addition to mineral composition and lithification process, geologists also classify sedimentary rock by its depositional characteristics, collectively called facies or lithofacies. Sedimentary facies consist of physical, chemical, and/or biological properties, including relative changes in these properties in adjacent beds of the same layer or geological age. Facies are groupings of rock types based on similar features. We use these groupings to generalize individual properties into useful, genetically related categories. 8. How do chemical, biochemical and organic sediments/rocks differ? Inorganic chemical sedimentary rocks form in environments where ion concentration, dissolved gasses, temperatures, or pressures are changing, which causes minerals to crystallize. Biochemical sedimentary rocks are formed from shells and bodies of underwater organisms . Clastic sedimentary rocks are made from rock and mineral fragments that are compressed and cemented together to make a rock. Chemical sedimentary rocks precipitate from a fluid. Sometimes the precipitation is aided by organisms. Organic sedimentary rocks are made from the bodies of plants and/or animals . 9. Be able to recognize the various sedimentary structures and have a general understanding of what each structure tells us about the environment of deposition. Examples: a. Ripple marks, cross beds indicate moving water or wind b. Mud cracks, raindrops indicate alternating wet/dry and a very quiet environment c. Bedding indicates deposition in some type of collecting basin d. Salt crystals mean evaporation Module 4 - Geologic Time 1. Know your unconformities! Review the multitude of annotated pictures in the text. An unconformity, a boundary between a group of older rocks below and the younger rocks above. Unconformities are classified according to their genesis as either angular unconformities, paraconformities, disconformities, or nonconformities. A nonconformity represents an erosional surface separating rocks of different types. The erosional surface will separate igneous and/or metamorphic rock from overlying sedimentary rock A disconformity is a little harder to discern: it is not as obvious as the previous examples. Disconformities occur between parallel sedimentary layers. Several exist in the horizontal layers of the Grand Canyon.

Disconformities are akin to paraconformities, but are usually easier to recognize because of irregular topography at the contact between sedimentary rocks. Nonconformities are the only type where the rock below the hiatus is not sedimentary rock, but rather igneous or metamorphic rock that has been planed-off before sediments were deposited over them. 2. Know how to identify your geologic structures: anticlines vs. synclines; normal vs. reverse faults; right lateral vs. left lateral strike slip faults; intrusive dikes 3. What type of stress produces each of the geologic structures mentioned above? 4. Know the different principles of relative dating: uniformitarianism; superposition, horizontality, lateral continuity; cross-cutting, inclusions, baking; faunal succession 5. Review the labs and diagrams in the text and be able to put geologic events in order from oldest to youngest. 6. What is absolute dating? How does that differ from relative dating? The differences between relative and absolute age dating are: Absolute age dating represents an age based on the half-lives of radioactive minerals whereas, relative age does not characterize specific age . Absolute age is found by using radioactive minerals in the rock. 7. What is the half-life of a radioactive isotope? Half-life is the length of time it takes for half of the radioactive atoms of a specific radionuclide to decay. A good rule of thumb is that, after seven half-lives, you will have less than one percent of the original amount of radiation . 8. Be able to determine the age of a sample by using the half-life diagram. 9. Familiarize yourself with the geologic time scale.