Syllabus: EES 1000, Sec 13, Dynamic Earth or Physical Geology, 3-4:15 PM, T&Th, Spring, 2006

Ronald K. Stoessell - Office 1034, Lab 1059, (504) 280-6795, rstoesse@uno.edu or ronlondi@charter.net

Text: Earth Revealed by Carlson, Plummer, and McGeary, 6th Edition

Tests: Three 100 point multiple-choice tests. The first test will cover chapters 1-6; the second test will cover chapters 7-12; and the last test will cover chapters 13-19 on 5/9/06 at 3-5 PM during finals. A comprehensive Makeup test covering Chapters 1-12 will be given immediately after the final test to serve as a makeup for students missing one of the first two tests. In addition, any student who wishes to substitute the Makeup test for one of their first two tests can take it. Students who miss both of the first two tests should drop the course. Students caught cheating will receive a grade of zero on the test.

The numerical grades of the three tests will be averaged and the course grade format is 87 ≤ A < 100, 74 ≤ B < 87, 61 ≤ C < 74, 49 ≤ D < 61, F < 49. Extra point questions may be given on a test but will not be given on the Makeup. Your test grades and overall course grade can be viewed using Blackboard.

Please sign the roll at the front desk at the beginning of each class. Attendance is not used in the grade computation but is taken to comply with federal regulations.

For office hours, email me at rstoesse@uno.edu or contact me before or after class to set up an appointment. Otherwise, look for me in the Geochemistry Lab (GP 1059) or in my office (GP 1034) on class days in the afternoon.

Lecture and Test Schedule - Note the test dates, together with the chapters covered on each test, are fixed but the date that a chapter is covered may differ from that below. If the lecture material for a test is covered before the test date, a review will be held on the last class day before a test.

         Chapters                 Chapters                    Chapters
  
 1/31/06    1            3/16/06     9              4/27/06      17             
 
 2/02/06    1 & 2          21        10              5/02/06     18                 
 
   07       2              23        11                04        Review                
                                                                                       
   09       3              28        12                09        3rd test 3 PM (final) 13-18                
                                                                makeup covers chapters 1-12                       
   14       4              30        Review                       given after the final
                                                                
   16       5            4/04/06     no class - study day                         
                                                                
   21       6              06       test (7-12)              
                                                                
   23       6              11       13                 
                                                  
 3/02/06    test (1-6)     13       14           
  
   07       7              18       15                              
 
   09       7 & 8          20       16                 
 
   14       8              25       16                 
 
                                     
 

Review Topics for Chapter 1 - Introducing Geology and an Overview of Important Concepts

Notes on this chapter were updated by the instructor for spring 2006.

• What do we study in physical geology?

• Understand the principle of uniformitarianism and how geologists use it to identify environments of formation of ancient rocks exposed in outcrops. Know the 4 steps of the scientific method, i.e., (1) gather data, (2) develop a hypothesis to explain the data, (3) test the hypothesis by making predictions, (4) if predictions are correct, hypothesis becomes a theory.

• How old is the earth? What are the four major concentric shells of rock and molten magma that make up the earth? Which is solid and which is liquid? Which is composed of iron with minor nickel and which is composed of silicates? What makes up the lithosphere? Where is the asthenosphere and how would you describe its state: solid, liquid, or plastic? Which igneous rocks make up the oceanic crust, the continental crust, the uppermost mantle,and the asthenosphere?

• What are convection cells and how do they move the plates in plate tectonics? What is the average rate of movement of the plates? What are the three major types of plate boundaries and what occurs at each type of plate boundaries? Know examples of each? There are three possible combinations of leading plate edges during convergence. Understand what happens in each scenario. Where are the oldest rocks in oceanic crust, and where are the youngest rocks in continental crust? Why is there more continental crust today than in the past? Where is new oceanic crust created and where is new continental crust created? How does a hot spot form and give an example? Where are new oceans forming today? What type of plate boundary surrounds much of the Pacific Ocean? Which plate boundaries surround the North American Plate?

• What is meant by isostasy? Why do we think the crust is floating on the mantle?

Review Topics for Chapter 2 - Earth's Interior and Geophysical Properties

Notes on this chapter were updated by the instructor for spring 2006.

• Review the internal structure of the earth, the different types of crust and the underlying layer making up the lithosphere, and the location of the asthenosphere. What rocks characterize continental crust, oceanic crust, and the mantle. What occurs in the mantle that distinguishes the upper mantle from the lower mantle? To what parts of the earth's interior do stony meteorites and iron meteorites correspond to. WHy do we think the age of meteorites correspond to the age of the solar system. How do we explain the denser elements like iron being at the center of the earth and the lighter elements being closer to the surface.

• Understand the refraction (changes in direction) and velocity changes for S and P seismic waves as they pass through the interior of the earth and where their shadow zones occur on the opposide side of the earth from where an earthquake occurs. What does the Monhrovic (Moho) discontinuity refer to? Why do the seismic waves follow a curved path? Do they travel faster in oceanic or in continental crust? Why do both P and S waves speed up as they pass from the crust into the uppermost mantle and then slow down as they pass through the asthenosphere (low velocity zone) before picking up speed in both the upper mantle and again in the lower mantle. Know why P waves slow down in the outer core and then speed up in the inner core, and why S waves do not pass through the outer core.

• In general, how do density, temperature, and pressure change from the surface to the center of the earth? What is meant by the geothermal gradient? In what direction does heat flow within the earth? What is the source of the heat? Why do we think the geothermal gradient decreases with increasing depth below the earth's surface.

• How does the strength of the earth's gravity field support the idea that the core is mostly iron? Where do we find positive and negative gravity anomalies on the earth surfaces. Understand that in each case the anomaly reflects an increase (if positive) or decrease (if negative) in mass between a point over the surface and the center of the earth and this is related to the concept of isostasy in which the crust floats on the mantle. Know the type of anomaly associated with diverging boundaries (positive), subduction zones (negative), mountains (negative), basins (positive), salt domes (negative), metal deposits (positive). Review the concept of isostasy and understand why mountains rise back up after being eroded down and basins sink with the deposition of more sediment. Why is coastal Louisiana sinking? What causes crustal rebound?

• How do we know the earth isn't just a huge bar magnet? What is meant by the Curie Point of a mineral or rock? What is the origin of the earth's magnetic field and why are the N and S magnetic poles close to the N and S geographic poles? What is meant by the declination of the earth's magnetic field at a point on the earth's surface. What is meant by the inclination of the earth's magnetic field at a point on the earth's surface. By measuring the residual magnetism in a rock, the location of the N and S magnetic poles and the magnetic latitude can be determined at the time the rock formed. Why do ancient rocks of the same age on different continents often have residual magnetism showing different locations of the magnetic poles? In general, how do the locations of the magnetic poles change with time? How often do the earth's N and S magnetic poles reverse? Why do symmetrical negative and positive magnetic anomalies occur on each side of the oceanic ridges?

Review Topics for Chapter 3 - The Sea Floor

Notes on this chapter were updated by the instructor for spring 2006.

• The shallow continental margin is called the continental shelf, the continental slope connects the deep sea floor with the continental shelf. The intersection with the sea floor is called the continental rise because this is where most of the sediment, moving down the continental slope, is deposited, i.e., the turbidity current deposits and abyssal fans. A current moving parallel to the continental margin carries sediment along the continental rise. Seaward of the continental rise are the abyssal plains which are flat due to sediment from the continental margins. Seaward of the abyssal plains are the abyssal hills which lack the sediment input from the continental margins to cover the hills. In the middle of the ocean basin are the spreading ridges with a rift valley in the center where new oceanic crust is being created. Oceanic crust is young (less than 200 m.y. old) compared to continental crust because eventaully it will be destroyed in subduction zones after moving away from the ridge. (Remember that the Earth has a finite surface area so the generation of oceanic crust at the ridges must be balanced by the destruction of an equal amount of crust in subduction zones.) The spreading ridges are high because the crust expands due to the heat of the magma moving up from the asthenosphere. As the crust moves away from the spreading ridges, it shrinks and the seafloor becomes deeper. Island volcanoes often sink below sea level to become seamounts (submarine mountains) as the underlying crust moves away from the spreading ridges, and have flat tops due to wave erosion as they pass below sea level. These seamounts are called guyots.

• Carbonate reefs consist of polyps surrounded by a calcite or aragonite precipitate. Coral usually grows on top of dead coral and can stay close to the surface as sea level rises. The polyps are animals growing in warm water and must be close to the surface because they require light for photosynthesis due to a symbiotic relationship with single-cell algae (type of dinoflagellate) in their tissue. Reefs typically form fringing reefs along the edge of island volcanoes. As the island volcano becomes inactive and moves away from the magma source, it slowly sinks and the fringing reefs become separated from the shore line, becoming barrier reefs. Eventually, if the island sinks below the ocean surface, the barrier reefs may still be at the surface, and the island becomes an atoll with reefs along the margin and a lagoon in the center, over the sunken island.

• Typical oceanic crust consists of deep sea sediment [cherts (from siliceous oozes of plankton shells), limestones (from carbonate oozes of plankton shells), and shales (from pelagic clays of windblown dust from land) overlying pillow basalts, overlying vertical basaltic dikes, overlying gabbro. The vertical sequence is called an ophiolite sequence when it is found on continents in the vicinity of ancient subduction zones where oceaninc crust was subducted. Note that because the deep sea floor is undersaturated with respect to calcite and aragonite, the carbonate oozes are not deposited on the deepest parts of the sea floor. The depth below which calcite is undersaturated in in sea water is called the carbonate compensation depth.

• The strength of the Earth's dipolar magnetic field at the surface also has areas that show higher or lower values than the average value (called magnetic anomalies). The poles of the Earth's magnetic field are closely aligned with the geographic poles of rotation, consistent with the magnetic field being generated in the outer core as the result of the movement of molten iron due to the rotation of the earth. The magnetic poles rotate around the geographic poles with the difference being called the declination. The dip of the magnetic lines into the earth's surface is the magnetic inclination. This dip is 90^o at the magnetic poles and 0^o at the magnetic equator, similar to lines of geographic latitude between the geographic equator and poles. The polarity of the poles undergoes a reversal every few hundred thousand years or so in which the S magnetic pole becomes the N magnetic pole and vice versa. Rocks crystallizing from a magma will pick up a residual magnetism parallel to the Earth's magnetic field as they cool below their Curie temperature (a few hundred degrees Celsius). Rocks are unmagnetized above their Curie temperature.

• Magnetic anomalies are positive over iron-rich rocks or an area of sea floor having residual magnetism aligned with the present orientation of the earth's magnetic field and negative over areas containing sediment lacking iron (e.g., salt) or oceanic sea floor having residual magnetism of opposite polarity to the present orientation of the Earth's magnetic field. The formation of new sea floor at the diverging ridges continuously produces sea floor with residual magnetism parallel to the orientation of the Earth's magnetic field. Hence, there is always a positive magnetic anomaly over the spreading ridges. Away from the ridges, symmetrical magnetic anomalies occur due to past reversals of polarity of the Earth's magnetic field. Sea floor having a negative magnetic anomaly formed at a spreading ridge when the Earth's magnetic field was of opposite polarity to today's magnetic field.

Review Topics for Chapter 4 - Plate Tectonics

Notes on this chapter were updated by the instructor for spring 2006.

Continental drift (proposed by Alfred Wegener) had the continents moving about the surface of the earth, driven by tidal forces; whereas, seafloor spreading (proposed by Harry Hess) has oceanic crust created at the mid-oceanic ridges, moving away from the ridges, and being destroyed in subduction zones. Plate tectonics is a further development of seafloor spreading in which the evidence used to support continental drift also supports plate tectonics.

In the 1910s, Wegener supported continental drift using evidence from the rocks that past climates differ from present climates (e.g., coal beds occur in Antarctic), glacial evidence showing the striations in bed rock on continents cut by ancient glaciers in the southern hemisphere require glaciers to have moved from water onto land (which cannot happen and is explained by putting South Africa adjacent to South America), fossil evidence showing identical Late Paleozoic and Early Mesozoic species of terrestrial organisms inhabited different continents that are today separated by oceans (e.g., fossils of large freshwater and terrestrial reptiles and the Glossopteris seed ferns), the jig-saw puzzle fit of continents if put back together (just look at a map of the globe), the continuation of geologic features (e.g., mountain ranges) when the continents are put back together, and the occurrence of similar geologic sequences of beds in the late Paleozoic on continents today that are widely separated by oceans (e.g., the Gondwana sequence in India and the southern hemisphere continents).

Wegener proposed that a super continent Pangaea had existed in the Late Paleozoic which had broken up in Late Mesozoic and the Early Cenozoic. Wegener thought continental crust plowed through oceanic crust. However, Wegener couldn't find a force capable of moving the continents and his late breakup of Pangaea did not give enough time for evolution to produce the different species found today on separated continents. Critics used these objections to shoot down continental drift. Today, Pangaea is thought to have broken up throughout the Mesozoic and mantle convection currents are postulated to provide the force to move rigid plates of lithosphere, containing oceanic and/or continental crust together with the uppermost mantle.

Hess proposed seafloor spreading in the early 1960s and it rapidly evolved into plate tectonics with plates of lithosphere moving on top of convection cells in the asthenosphere. Hess was trying to explain the occurrence of the mid-oceanic ridges (where new seafloor is created) and the trenches and associated Benioff seismic earthquake zone (where the oceanic crust is destroyed). Matthew and Vine used Hess's ideas to explain the symmetrical magnetic anomaly pattern in seafloor relative to the mid-oceanic ridges, which resulted in rapid acceptance and expansion of the theory .

Plate tectonics explains many observations and relationships of the earth's crust and upper mantle. You need to understand those listed below:




• The relationship between the plastic asthenosphere and the overlying lithosphere in which the deformation of the plastic asthenosphere carries the plates of lithosphere (the movement is in convection cells arising from heat flowing from the core and mantle to the surface);

• The presence of trenches in the seafloor and the nearby Benioff zone of shallow to deep earthquakes (marking subduction zones of oceanic lithosphere) and the overlying composite volcanoes (formed from partially melting the subducted lithosphere including oceanic sediments which results in forming new continental crust);

• The sequence of an accretionary wedge (melange), forearc basin, composite volcano, metamorphic complex with folded sediment, and backarc basin associated with a subduction zone and the characteristic sediment sequence in a backarc basin;

• The presence of the mid-oceanic ridges with shield volcanoes and rift valleys and the origin of the symmetrical magnetic anomalies to the mid-oceanic ridges (due to magma from melted and partially melted peridotite in the mantle, coming up to form new lithosphere (oceanic crust and uppermost mantle) and picking up residual magnetism from the earth's magnetic field as it cools below its Curie point);

• The presence of chains of inactive (aseismic) submarine volcanoes with one active shield volcano at one end (marking a hot spot where magma is coming up from the mantle and burning a hole through the overlying moving plate);

• The presence of mountains made of folded sedimentary rock (where continental crust sutures to continental crust, e.g., the Alps, Urals, Himalayas, Appalachians).

• The presence of major shallow earthquakes along faults that mark the boundary where one plate moves past another, e.g., the San Andreas fault;

• The young age of oceanic crust (< 200 m.y.) and the increase in age from the mid-oceanic ridges to the margins and the old age of continental crust (up to 4 b.y.) in which the stable interiors of continents contain the oldest rock;

• The occurrence of isolated areas of oceanic crust within the accretionary wedge of subduction zones (ophiolites);
  
  
• The presence of faults connecting ridge offsets on the mid-oceanic ridges in which the motion of movement is opposite to that required if the ridges were moving apart along the offsets; and

• The presence of salt deposits, red beds, and basaltic lava flows when continents are rifted apart (e.g., the Louann Salt and the Eagle Mill Red Beds in Louisiana mark the rifting of Pangaea).

The theory doesn't easily explain the presence of large earthquakes within the center of plates, e.g., the Charleston earthquake and New Madrid earthquake (in Missouri) in the 1800s, or the formation of large mountains far from plate boundaries, e.g., the Rocky Mountains.

Geologists date the seafloor using radiometric dating (and other methods), measure the distance from the mid-oceanic ridge (where the seafloor formed) and divide the distance by the age to come up with the rate of movement of a plate. The movement is a few cm/year (slowest in the Atlantic and more rapid in the Pacific). For quick dating of the seafloor, geologists often use the positions of the symmetrical magnetic anomalies on the seafloor that are caused by the polarity reversals of the earth's magnetic field. Those reversals have been previously dated radiometrically, using stacked sequences of lava flows on land. The reversals are identified in the magnetic anomalies on the seafloor which establishes the age of the associated seafloor. Note that today, we can actually measure the slow rate of movement using accurate surveying techniques, e.g., use a laser to measure the change in separation between two continents over a year's time.

Be sure you understand what happens at diverging, converging, and transform plate boundaries. In particular, what occurs at converging boundaries when the converging crust on the leading edges results in (1) oceanic crust meeting oceanic crust, (2) oceanic crust meeting continental crust, and (3) continental crust meeting continental crust. Know where new oceans are forming today. Understand what is happening in the Red Sea, Gulf of Aden, and East African Rift Valley.




Review Topics for Chapter 5 - Mountain Belts and the Continental Crust

Notes on this chapter were updated by the instructor for spring 2006.

Back to List of Chapters


Continents consist of the stable interior called the craton which is often covered with a thin (few thousand feet) thick layer of sediments. The Precambrian shield is that portion of the craton with the oldest rocks, Precambrian rocks, exposed at the surface. Mountain ranges on continents and island arcs generally form on the margins along converging plate boundaries. Mountains forming over subduction zones mark areas where partial melting of a subducted plate is adding new continental crust. Continental crust is never destroyed, meaning that the percentage of the earth's surface area occupied by continents has gradually increased since the earth was formed; however, the rate of increase has decreased as the earth gradually cools due to smaller amounts of radioactive decay in the interior. When plate tectonics eventually stops, no new continental crust will form and the mountains will eventually be eroded to a flat plain.

Please read the information below and be sure you understand the points that are mentioned



• If a subduction zone exists along a continental margin, the rising magma produces a series of composite volcanoes overlying granitic rock, e.g., the Andes on the west coast of South America and the Cascades on the west coast of North America. These are tall mountains with steep slopes. The location of the volcanoes depends upon the dip of the subduction zone because the subducted plate must reach a sufficient depth to be partially melted before the magma is generated. Landward of the volcanoes is the backarc basin (also known as the foredeep basin) which typically has sediments grading upward from shallow marine at the base of the basin, into deepwater marine (flysch), into shallow water marine, into fluvial freshwater marine (molasse). The sedimentary sequence is due to downwarping of the continental margin as subduction begins and the gradual filling of the resulting basin.

• If subduction ceases because converging stops, the volcanoes will be eroded away, causing the crust to rise by block faulting (isostatic adjustment - because the crust is floating on the mantle and erosion has removed weight) bringing the granitic rock to the surface, e.g., the Sierra Nevada Mountains in eastern California, and the Rocky Mountains further east. To erode the mountains down to a flat plain requires many cycles of erosion and uplift, each of which results in mountains of lower elevation than in the preceeding cycle, e.g., the Appalachians. So older mountains are typically composed of granite and are generally lower in elevation than younger mountains.

• A subduction zone along a continental margin will also stop if the oceanic crust is completely destroyed, bringing continental crust converging against continental crust. Continental crust is too light in density to be subducted so the two plates will fuse together. Thick sediment deposits along the margins of the continents are squeezed and pushed upward as the plates suture together, The uplifted sediment layers slide slowly by gravity away from the suture boundary and are eroded into mountains. The layers of sediment sliding by gravity are called nappes and are always folded in the process of sliding. Examples of mountains formed due to suturing are the Himalayas, Alps, Pyrenees, and Urals. Mountains composed of sediment erode into much sharper peaks than those composed of granite which have rounded summits. Eventually, as erosion removes the sediment, isostatic adjustment occurs, lifting the area back up, exposing the continental crust underneath, e.g., the Appalachians.

• The suturing process described above can result in suturing two large continents together. More often, the process sutures a small body of continental crust, e.g., an island arc, to a larger continent. These smaller bodies are then called terraines. Note that a terraine can also be added to a continent by moving it into position along a transform fault, a process that has built up British Columbia and Alaska.

• If an island arc is sutured to a larger continent, a new subduction zone can develop on the seaward side of the island arc, so oceanic crust is again subducted. Eventually, the destruction may bring a new island arc into position adjacent to the continent, and it too will be sutured to the larger continent. The process allows the continent to continue to grow along its margins.

• Other mountain chains exist along mid-oceanic ridges, consisting of shield volcanoes which become inactive as the underlying seafloor moves away from the ridge. In addition, a chain of shield volcanoes can be produced as a plate moves over a hot spot in which the only active volcano is the one over the hot spot. Shield volcanoes are large mouontains with gentle slopes and rounded summits.

• Interestingly, when larger continents (e.g., Pangaea) split through the development of diverging boundaries under them, they tend to do so along earlier suture lines, preserving the outline of the smaller continents, e.g., the present Red Sea split between Africa and the Arabian Peninsula. The suture lines are thought to be zones of weakness in which the underlying uppermost mantle may become gravitationally unstable, detaching from the base of the continental crust and sinking into the underlying asthenosphere in a process called delamination. But this is only a hypothesis.

Review Topics for Chapter 6 - Geologic Structures

Notes on this chapter were updated by the instructor for spring 2006.

Back to List of Chapters


• Understand what is meant by stress and strain, e.g., which term corresponds to applied pressure and which one to the resulting deformation. Know the difference between elastic, brittle, and plastic deformation in rocks. Give an example of crustal rebound. What is the difference in deformation between a fault and a fracture or joint? Why is it that at deeper depths, folds are more likely to occur than faults?

• What are the definitions of strike and dip. From a cross-section (road-cut exposure) of beds, be able to recognize an anticline and a syncline. Also, from a cross section, be able to recognize an overturned fold, an open (normal or symmetrical) fold, a recumbent fold, and an isoclinal fold. Know how to identify an anticline and syncline by the relative age of beds exposed in their surface outcrops. Be able to recognize an anticline, syncline, dome, and basin from a surface map showing strike and dip symbols. Know how to use the nose of a plunging fold on a surface outcrop to determine the direction an anticline or syncline is plunging.

• Know the difference between strike slip and dip slip movement on fault planes? What types of stress creates a normal fault and reverse faults. Be able to identify in cross-section: a reverse fault, a normal (gravity) fault, and a thrust fault; and from surface view: a left lateral strike slip fault and a right lateral strike slip fault. At which plate boundary would you expect to find strike slip faults, to find reverse faults, and to find normal faults? What is the San Andreas fault? How do we explain the formation of rift valleys on the top of spreading ridges (divergent plate boundaries).




Review Topics for Chapter 7 - Earthquakes

Notes on this chapter were updated by the instructor for spring 2006.

Back to List of Chapters


• How does elastic rebound explain the release of the seismic energy of an earthquake? What is the epicenter and focus of an earthquake? Why is their a depth limit for the focus of an earthquake? At what plate tectonic setting are the deepest earthquake foci located? Why is there a limit to the amount of energy released during an earthquake?

• Know the 3 types of earthquake (seismic) waves: the P (primary or compressional) body wave, the S (secondary or shear) body wave, and the surface waves (the L or Love waves and Rayleigh waves) and the particle movement associated with each wave type. Know the relative speeds and relative amplitudes of each type of wave (relative to each other). How is inertia used in a seismometer to delineate ground motion during an earthquake?

• Understand the general depth change in density within the earth. How does the wave velocity and wave direction change going from a less dense to a more dense medium? How do body waves change in velocity and direction as they pass through the earth's interior. How were the asthenosphere, the Moho, the outer core and the inner core detected with body waves? Which wave type cannot travel through the outer core and why? What are the locations of the S and P shadow zones on the opposite side of the earth from where the waves are generated at the focus?

• Explanation - Because the waves move through a medium by deformation of the medium, the velocity is related to how fast the medium deforms (undergoes strain) when stress is applied to it. The deformation as the result of applied stress is called the elastic modulus. The square of the wave velocity is directly proportional to the reciprocal of the density in which the the elastic modulus is the proportionality constant. This constant (elastic modulus) generally increases with density so that the velocity of seismic waves also increase with density.

• What are travel time curves and how are they used to locate the epicenter of an earthquake (the point on the earth's surface over the focus where the earthquake occurred)? How many seismograph stations are needed to do this.

• What does the Mercalli "intensity" scale measure? What does the Richter "magnitude" scale measure? An increase of one unit on the Richter scale represents an increase of how much energy released. An increase of two units represents an increase of how much energy released. What is the approximate maximum magnitude possible?

• On what plate boundaries do shallow earthquakes and deep earthquakes occur? What is a Benioff zone? What are the indicators used to predict earthquakes? How can an earthquake be initiated to release stress along a fault? What is meant by a seismic gap along a fault?

• What causes liquefaction during an earthquake? What types of ground and buildings are most resistant to earthquakes? How is a tsunami generated during an earthquake?




Review Topics for Chapter 8 - Time and Geology

Notes on this chapter were updated by the instructor for spring 2006.

Back to List of Chapters


• Understand how to use the principles of "original horizontality, superposition, cross-cutting relations, and inclusions" to determine relative age of different rocks. Be able to use them to establish relative age in a vertical cross-section of a rock sequence. What rock layers can form nearly constant time lines?

• How is the principle of biota (faunal and flora) succession used to establish a relative time sequence of the occurrence of fossils in rocks that outcrop in widely separated areas? What are the three characteristics of an index fossil? What is a trace fossil? What can cause mass extinctions and how often have they they occurred in the past?

• What is meant by an unconformity? Know the three types of unconformities (nonconformity, disconformity, and angular unconformity) and be able to recognize them in a vertical cross section of a rock sequence.

• Understand how the occurrence of Ice Ages and changes in rates of sea-floor formation at spreading ridges can cause sea level to rise or fall. Understand how to identify a rising sea level (transgressive sea) from a falling sea level (regressive sea) in a core taken in a coastal area.

• What must be known to apply radioactive dating using an unstable isotope. What are the three ways that a radioactive isotope breaks down and how does each affect the atomic mass and atomic number. What is meant by the half life of a radioactive isotope? Do different radioactive isotopes have the same half life or different half lives?

• If the number of radioactive atoms of an unstable isotope decrease from 2000 to 250, how many half lives have occurred and what time period has passed, assuming a half life of 1 m.y.? What would the answer be if the number of radioactive atoms had decreased to 1/8th of that present initially?

• The geologic time scale. Learn in proper sequence, the 4 eons (include the Hadean), the 3 eras of the youngest eon, the 13 periods (use Paleogene and Neogene for Tertiary) of those 3 eras, and the 7 epochs of the youngest era, together with the age breaks at the beginning and end of each eon and era.
  
  For extra points, know that the following evolutionary sequences of invertebrate and land plants and when the two great mass extinctions were in the earth's history.
  
  Jawless fish evolved in the Cambrian Period, giving rise to jawed fish (jaws evolved from gill supports and teeth from scales) in the Ordovician Period from which came ray-finned fish, sharks, and lobe-finned fish in the Devonian Period. The fin bones on lobe-finned fish are similar to our arm and leg bones. In late Devonian, amphibians evolved from lobe-finned fish, developed lungs, and moved into the coastal areas but not the dry interior because they have an aquatic juvenile stage. Reptiles evolved from amphibians in the Pennsylvanian Period. Reptiles reproduce using the amniote egg which allowed them to colonize dry land. In the Triassic Period, the reptile group known as the thecodonts gave rise to the dinosaurs and pterosaurs (flying dinosaurs) and the mammal-like reptile group known as the therapsids gave rise to mammals. Later, in the Jurassic Period, birds evolved from the group of dinosaurs known as the lizard-hipped dinosaurs. Dinosaurs and pterosaurs disappeared at the end of the Cretaceous Period.
  
  The evolutionary sequence of higher plants from algae began in the Ordovician Period with the appearance of spore-bearing plants which evolved a vascular sustem (required to have a trunk) by the Devonian Period. Spore-bearing plants require moist conditions to reproduce and were limited largely to coastal areas. In the Devonian Period, gymnosperms, naked seed-bearing plants, evolved and colonized dry land. Pines and cypress trees and cedars and sego palms (cycads) are gymnosperm examples. Angiosperms, flower-bearing plants, evolved in the Cretaceous Period from gymnosperms and are the dominant plants today (including trees such as oaks).
  
  The greatest mass extinction occurred at the end of the Paleozoic Era (end of the Permina Period) and the second greatest mass extinction was at the end of the Mesozoic Era (end of the Cretaceous Period). In general extinctions follow a 26 million year cycle and are marked by irridium-rich layers in the rock record, indicating metereorite hits and giving rise to the death star hypothesis; however, extinctions may also occur due to climate changes such as world-wide glaciation.




Review Topics for Chapter 9 - Atoms, Elements, and Minerals

Notes on this chapter were updated by the instructor for spring 2006.

Back to List of Chapters


• Know the definition of a mineral and an element. Why isn't obsidian a mineral? Is ice a mineral? Understand the difference between an atom of an element and a molecule of a compound. Understand electrons, protons, neutrons, nucleus, electron cloud, atomic mass, atomic number, ions (anions, negatively charged; cations, positively charged), and isotopes (atoms of the same element with different number of neutrons in nucleus. Know the differences between ionic bonding, covalent bonding, Van der Waals bonding, and metallic bonding. Know the common chargtes on atoms of common elements, e.g., H⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺, Fe²⁺ and Fe³⁺, Al³⁺, Si⁴⁺, C⁴⁺, S⁶⁺, Cl^-, F^-, S^2-, O^2- and know how this information can be used to predict how atoms combine with ionic and covalent bonding to form compounds. What controls crystal form, cleavage and color. Know the meaning of fracture, streak, luster, hardness, and density (specific gravity). Which mineral commonly shows double refraction to the naked eye. Which minerals react with acid by fizzing to release carbon dioxide.

• Understand polymorphs. Why does calcite form rather than argonite or diamond form rather than graphite. Why does the metastable form persist.

• Mineral groups are commonly named after the principal anion group. The Silicates contain the anion group (formed with covalent bonding), SiO₄^4-, made up of the two most common elements in the earth's crust. Si is bonded or linked with O around it to form a tetrahedron (Egyptian pyramid shape), and different silicate groups form from different ways of linking these tetrahedron together. Different minerals within each group have different substitutions of Si⁴⁺, e.g., substituted with Al³⁺ amd K⁺ to make K feldspar in the framework silicates or or substituted with 2Mg²⁺ in the single chain silicates to make olivine. Understand how the tetrahedron are linked together in the different major silicate groups and know the major mineral example(s) of each group: isolated or single (olivine), single chain (pyroxenes), double chain (amphiboles), sheet (biotite, muscovite, clay minerals), and framework (quartz, K feldspar or orthoclase, Na feldspar or plagioclase, Ca plagioclase).

• Oxides and Hydroxides contain O^2- and OH^- as the principal anions. Know the major examples, e.g., the iron oxides and hydroxide (hematite, Fe₂O₃; magnetite, Fe₃O₄; and limonite, FeO(OH)), magnesium hydroxide (brucite, Mg(OH)₂), and aluminum oxide and hydroxide (corundum, Al₂O₃ and gibbsite, Al(OH)₃).

• Carbonates contain CO₃^2- as the principal anion and there are only four common carbonate minerals: calcite and aragonite which are calcium carbonates (CaCO₃) and are polymorphs, dolomite which is a calcium magnesium carbonate (CaMg(CO₃)₂), and magnesite which is magnesium carbonate (MgCO₃).

• Sulfides and sulfates contain S^2- and SO₄^2-, respectively, as the principal anions. The sulfides are the usual metallic ore minerals, e.g., galena (lead sulfide, PbS), sphalerite (zinc sulfide, ZnS), pyrite (iron sulfide, FeS₂). The sulfates are usually evaporite minerals, e.g., anhydrite (calcium sulfate, CaSO₄), gypsum (hydrated calcium sulfate, CaSO₄.2H₂O), and barite (barium sulfate BaSO₄).

• halides contain the anions: chloride (Cl^-) and fluoride (F^-) which are also usually evaporite minerals, e.g., halite (sodium chloride, NaCl), sylvite (potassium chloride, KCl) and fluorite (calcium fluoride, CaF₂, not an evaporite).

• Native elements are minerals composed of only one element, e.g., diamond and graphite (carbon polymorphs - both composed of C), gold (Au), native silver (Ag), and native copper (Cu).




Review Topics for Chapter 10 - Volcanism and Extrusive Rocks

Notes on this chapter were updated by the instructor for spring 2006.

Back to List of Chapters


• What are shield volcanoes and composite volcanoes composed of and where do they occur in the context of plate tectonics? What are cinder cones and where do they form? How is the magma generated for shield and composite volcanoes and which igneous rock is each composed of? What is a caldera and how does it form? Which type of volcano can form a volcanic dome? What is the difference between lava flows and pyroclastic flows and which type of flow typically occurs with the two main types of volcanoes and in cinder cones? What controls the viscosity of magma? What are flood (plateau) basalts?

• What textures are meant by pahoehoe, aa, pillow basalts, columnar jointing, vesicular basalt, scoria? What are pumice, cinders, ash, bombs, and blocks? What is obsidian and how does it form?

• Which volcano type is dangerous and why? Which volcanoes have fire fountains and which volcanoes have eruption columns? How does a lave flow move a long distance from a volcano without crystallizing into solid rock? What is the difference between a lava flow and a pyroclastic flow? What is a tuff (and welded tuff), an ignimbrite, a nuee ardente, a surge deposit, a lahar? Which deposit will likely be volcanic breccia?

• How do volcanic eruptions affect the earth's surface temperature?




Review Topics for Chapter 11 - Igneous Rocks, Intrusive Activity, and the Origin of Igneous Rocks

Notes on this chapter were updated by the instructor for spring 2006.

Back to List of Chapters


• Know the definition of an igneous rock? What is the difference between lava and magma? What is the difference in texture between intrusive and extrusive igneous rocks and what causes it? What is porphyritic texture (phenocrysts and goundmass) and what causes it? What is a pegmatite and why does it have large crystals?

• What are plutons, batholiths, xenoliths, stocks, dikes, and sills?

• Learn the intrusive and extrusive igneous rocks with their minerals corresponding to ultramafic (komatite and peridotite, composed of the minerals olivine and pyroxene), mafic (gabbro and basalt composed of the minerals olivine, pyroxene, and Ca plagioclase), intermediate (diorite and andesite, composed of the minerals amphibole, biotite, and Na plagioclase), and felsic (granite and rhyolite, composed of the minerals muscovite, K feldspar, and quartz). Why are komatites so rare? Know Bowen's reaction series?

• Learn the trends in melting or crystallization temperatures (high to low), chemistry (rich in Fe, Mg, Ca to rich in Si, Na, K), and melt viscosity (watery to sticky in rocks or magma ranging from ultramafic to felsic. How does the water content of a magma affect the crystal size, the viscosity, the crystalliztion temperature?

• What is the geothermal gradient? How does partial melting of a mafic rock and crystal settling (fractional crystallization) from a mafic magma result in forming more felsic rocks than the parent rock or magma? How does partial melting explain the basaltic magma occurring at spreading ridges and hot spots and the andesitic magma occurring over subduction zones?

• How do hydrothermal rocks form? Know an example.




Review Topics for Chapter 12 - Weathering and Soil

Notes on this chapter were updated by the instructor for spring 2006.

Back to List of Chapters


• Sediment forms from weathering, an earth-surface process which is the physical and chemical breakup of rock. Note that this is different from erosion which is the movement of weathered material to a position where it can undergo transportation by a stream, a glacier, wind, etc. Weathering can continue during transportation.

• Physical (mechanical) weathering processes include frost wedging by freezing and thawing of water in cracks. Frost heaving on hillsides will result in creep downslope of the surface (an erosion process). Exfoliation results by erosion of the overburden, producing sheet joints by pressure release (producing the rounded domes characteristic of granite). Other examples of physical weathering include root pressure in cracks, expansion and contraction of rock caused by temperature changes, abrasion at the bottom of a glacier or in a pothole in a stream or by sand in a sandstorm producing ventifacts, hydraulic force of waves along the coast, the activities of humans, etc. The most effective process is frost wedging which occurs most rapidly in temperate climates which have frequent temperature swings above and below freezing.

• Chemical weathering involves chemical reactions which works fastest on areas with the greatest surface area. Chemical weathering requires water. Most weathering reactions take place faster under acidic conditions. Absorption of gaseous CO₂ into water makes it a weak acid, causing slow transformation of silicate minerals into clays to form soils and rapid complete dissolution of carbonate minerals, e.g., calcite in limestone, that can result in forming sinkholes and underground rivers (karst topography). The source of the CO₂ is the respiration of bacteria in the soil. Absorption of gaseous O₂ from the atmosphere into water makes it an oxidizing agent for chemical reactions such as the oxidation of iron which turns the sediment and soil color to yellow, brown, and red. Chemical weathering increases with increasing earth surface temeprature and with the avalability of water, i.e., the process is most effective in a tropical rain forest. Because chemical weathering works inward from the rock surface, edges which have more surface area are weathered more rapidly, producing a rounded surface with a minimum of surface area. e.g., spheroidal weathering".

• The element aluminum (Al) cannot be removed by carrying it away in ground water as a dissolved component. Instead, Al is used to form a clay mineral "in place" and these clay minerals are needed for soils. They hold plant nutrients on their surface. So a weathered rock must have aluminum in it to weather to a soil, e.g., the rock must be an aluminum silicate and not a carbonate rock such as a limestone or not made up of completely soluble evaporite minerals such as halite or gypsun. Weathering rates for aluminum silicate minerals are greater for the igneous minerals that crystallize at higher temperatures, e.g., minerals in a basalt/gabbro weather more rapidly than those in an andesite/diorite which weather more rapidly than those in a rhyolite/granite. The stable minerals that form from chemical weathering are quartz, aluminum-silicate clays, iron oxides, and calcite (in desert regions without water). The presence of quartz in the parent rock makes the soil more sandy and increases the permeability of the soil to the movement of water.

• Differential weathering refers to the differences in weathering of different types of rock, e.g., shales weather more rapidly than sandstones which accounts for shales forming valleys and sandstones forming ridges.

• Soils are divided into horizontal layers. The soil color is controlled by organic matter staining it dark and iron oxides staining it dark when the iron is reduced and brighter colors when the iron is oxidized . The O horizon on the surface is composed of organic material. The A horizon just below is composed of both organic material and minerals, namely clay minerals, quartz grains, and iron oxides and is subject to leaching from rainwater passing through. The leaching carries clay minerals and iron oxides downward and any soluble components from dissolution. The underlying E horizon lacks organic material and is a lighter color than the A horizon and is also subject to leaching. The color of the E horizon is used to delineate wetland (hydric) soils which are delineated as wet if grey in color and non-wet if brighter (more yellow) in color. Under the E horizon is the B horizon where hard pan forms by accumulation from the leaching and also (in desert regions) where accumulation occurs from ground water moving upward in the capillary fringe, e.g., from salts in these waters which precipitate out as the waters evaporate in the desert near the surface. The accumulation in the B horizon can produces hardpan layers of clay minerals (clay pan), iron oxides (iron pan), and calcite (caliche from precipitation). The C horizon is the zone of partially weathered "in situ" rock which is missing in the transported soils.

• Desert regions have well-developed B horizons at the surface and almost no A horizons in soils named pedocals. In desert soils, water evaporation pulls ground water up from below, causing precipitation of hard pan of calcite (caliche) near the surface. Temperate soils have both well-developed A and B horizons in soils named pedalfers. Hard pan layers of clay and iron oxides are common in pedalfers. Tropical rain forests have extremely well developed A horizons in soils named laterites which (because of extensive leaching) are composed only of Al and Fe oxides with little organic matter remaining. These soils bake into bricks when exposed to the sun by removal of the rain forest. Extreme leaching produces bauxites, composed only of Al oxides. Bauxites are commonly mined for their Al content.

Review topics for Chapter 13 - Mass Wasting

• What is the driving force causing mass movement (mass wasting) and what force opposes this movement?

• What is the difference in movement between a "fall", a "flow" and a "slip" or "slide"? Does a "slump" occur as a flow or a slide or does it have both types of movement?

• How do the following factors affect slope stability: hillside steepness, thickness of debris layer on slope, water content, vegetation, orientation of bedding layers and foliation layers relative to the hillside.

• What is a talus slope and what is meant by the angle of repose of a talus slope?

• Mass wasting produces what type of cross-sectional shape in a river valley?

• Understand how building homes on slopes generally decreases slope stability? What are the effects of an impermeable retaining wall, adding a swiming pool, adding an irrigation system, drilling into the hillside with large bolts.

• How can an earthquake cause liquifiaction (formation of quickclay and quicksand)? What causes solifluction? How does freezing and thawing cause "creep" on a hillside?

Review Topics for Chapter 14 - Sediment and Sedimentary Rocks

• What is the definition of a sedimentary rock and what are bedding planes? How does weathering, sediment transport, depositional environment, and lithification (compaction and cementation) form a detrital or clastic sedimentay rock? What happens to the grain size, sorting, and unstable minerals during sediment transport by rivers? What are conglomerates, breccias, sandstones, siltstones, and shales (mudstones)? In what depositional environments do the following sedimentary stuctures form (to be preserved in the rocks): small crossbeds, large crossbeds, symmetrical ripple marks, asymmetrical ripple marks, mud cracks, graded bedding? What are trace fossils? What depositonal environment produces a lack of sorting and no bedding?

• How does a chemical sedimentary rock form? What are limestones, evaporites (halite and gypsum), dolostones, chert, and coals and how do they form? What is meant by a bioclastic sedimentary rock? What depositional environment produces salt deposits? What is coquina and what is chalk composed of? Where does coal fomr?

• Detrital sediments are produced from weathered rock or from fragments of shells. They are cemented together after deposition by authigenic minerals that precipitate from ground water interacting with the sediment grains. Chemical sedimentary rocks can be direct precipitates from water such as halite or gypsum from evaporating seawater or calcite from degassing of CO₂ from water in caves or silica from high pH water in deserts.

• Sedimentary systems that deliver sediment to a depositional area include streams, wind, and glaciers. Deposition can occur in a variety of environments including stream deposits in floodplains, wind deposits in deserts, glacier deposits at the end of a glacier, lake deposits, deposits in nearshore marine environments, in deep marine environments along the continental margins next to the deep sea floor, and the deep sea or abyssal marine deposits.

• Streams make up the most important delivery system of sediments. The sediments decrease in size downstream, increase in roundness and sorting and undergo more chemical weatherng during transportation in a stream. The most resistant sediment grains to weathering are quartz grains which become more dominant further downstream in a channel. Streams have a flood plain composed of the channel, natural levee, and backswamp in which the sediment size decreases going from the channel bar deposits to the natural levee deposits to the fine-grained backswamp deposits. The natural levee and backswamp deposits are deposits from the river in flood. The channel-bar deposits in ancient rocks are recognized by small cross beds. The channel-bar deposits and the natural-levee deposits in ancient rocks have a shoe string geometry reflecting their deposition in and adjacent ot the stream channel. The backswamp deposits have a blanket geometry and often result in coal beds in ancient rocks. The delta at the mouth of a river contains distributaries separated by natural levees and back swamp areas. A river which does not end in a large body of water but in a valley in a desert produces an alluvial fan, a cone-shaped pile of sediment deposited as a river in flash flood flows out onto a desert floor.

• Lake or lacustrine deposits are often varved in which a thick lighter-colored summer layer alternates with a narrow and darker-colored winter layer.

• Glacier deposits are often hills of sediment that are unsorted, unrounded, and unbedded.

• Nearshore marine deposits include beaches which are characterized by symmetrical ripple marks. Detrital sediment in beaches, transported from the interior of the continent, are usually quartz sand. Carbonate sand on a beach usually comes from broken up reef rock, calcium carbonate-coated fecal pellets, and precipitated round grains of calcium carbonate called oolites.

• Turbidite deposits, along the edge of the continental margin and adjacent to the deep sea floor, have graded bedding and are the deposits from submarine landslides on the continental slope. Typically they are cone-shaped in geometry, similar to alluvial fans but called abyssal fans because of their location.

• Deep sea deposits consist of pelagic clays formed from clay-size material blown out to the oceans. Deposits of chert and calcium carbonate come from the plankton shells of opaline silica and of calcium carbonate. These shells form silica and carbonate oozes on the deep-sea floor which eventually lithify into chert and limestone, respectively. Note that carbonate oozes do not form in the deepest part ofthe ocean, because they tend to dissolve in deep sea water.

Review Topics for Chapter 15 - Metamorphism, Metamorphic Rocks, and Hydrothermal Rocks

• What is the definition of a metamorphic rock and what is meant by metasomatism? What is the highest possible temperature of metamorphism and what is a migmatite?

• Give specific environments where regional metamorphism and contact metamorphism occur?

• What produces foliation in a metamorphic rock? Know the characteristic features of the following foliated metamoprhic rocks: slate, phyllite, schist, and gneiss. What parent rock could poduce this sequence? What are the parent rocks of marble, skarn, quartzite, and hornfels?

• How do we determine the temperature and pressure of metamorphism? What is meant by metamorphic grade?

• What is the definition of a hydrothermal rock?

Review Topics for Chapter 16 - Streams and Floods

• Understand the hydrologic cycle. Water falls as rain, snow, or sleet from the atmosphere, infiltrates into the ground to become ground water and/or moves by overland sheet flow into streams. Streams receive input from ground water and eventually empty into the oceans. Evaporation and transpiration return water to the atmosphere. Some water is stored temporarily as ice in glaciers or as ground water in the pores of sediments.

• Streams carry sediment as fine-grain suspended material and coarse-grain bed-load material. The bed-load sediment moves by saltation (bouncing) and by traction (rolling) of the heaviest and largest sediment. The volume of water passing a point in the stream per unit time is the discharge. The discharge divided by the cross-section area of the stream channel is the specific discharge. The base level is the lowest level that a stream can erode its channel (usually sea level). The capacity of a stream is the maximum load of solids that a stream can move and the competence of a stream is the largest size particle that it can move.

• The stream gradient is the vertical drop in the channel divided by the horizontal distance over which the vertical drop takes place. The stream gradient becomes lower as the mouth of a river is approached. A river will switch channels when it can take a shorter route which increases its stream gradient. The Mississippi River wants to switch to the Atchafalaya River channel (north of Baton Rouge) to increase its gradient but the Army Corps of Engineers is preventing this from happening. Streams that are in equilibrium between their discharge, their sediment load, and shape of the channel are said to be graded streams.

• The floodplain of a stream includes its channel (has sand bars), natural levee (silt deposits near the channel), and back swamp area (clay deposits further away from the channel). Stream cut a V-shaped valley which is apparent in a narrow floodplain but not with one having a wide floodplain. Tributaries are smaller streams draining into a larger stream and distributaries are smaller streams draining away from the major channel. Generally, distributaries occur within a delta. A delta will be river dominated or wave dominated. The Mississippi River is river dominated, causing the bird foot shaped delta but the Amazon River is wave dominated, causing the sediment to be smeared along the coast. Stream terraces along the edges of the Mississippi River floodplain are old floodplains that were not eroded away when the stream cut a new floodplain surface due to lowering of sea level during the Ice Ages. Such terraces are common along floodplains. Incised streams have no floodplain other than the stream channel, e.g., the Colorado River in the Grand Canyon, and result form the downcutting of the stream occurring as the surrounding area is uplifted, causing the stream to be trapped in its channel.

• There are 2 general types of streams: meandering and braided. Meandering streams have thin and deep channels and have a meandering shape in which the sediment load is generally fine-grained and the discharge is generally constant. Meandering streams have their channel bars attached to the inside edge of meanders on the point bar side; whereas, erosion occurs on the outside of the meander or the cut bank side. Oxbow lakes are abandoned meanders due to the river cutting across the bend during a flood in order to increase its stream gradient. Braided streams form during flash floods in desert regions and in streams from melt water coming off glaciers. Braided streams have wide, shallow channels with mid-channel sand bars, coarse sediment, and a fluctuating discharge.

• Depending upon the resistance of the surface rock to erosion, stream drainage patterns develop. Understand the cause of these types: dendritic, rectangular, radial, and trellis? Understand the concept of a drainage basin and a drainage divide.

• Flood control devices on a stream include artificial levees (along the channel), dams (to temporarily store water), and spillways (to divert water). The Atchafalaya Spillway and the Bonnet Carre Spillway are used for flood control on the Mississippi River. Channelization is making a channel straight through artifical cutoffs. The water can be moved more quickly; however, the stream level at peak discharge will be higher downstream which can increase downstream flooding. The difference in time between an upstream rain event and the peak discharge at a point on the stream is the lag time.

Review Topics for Chapter 17 - Ground Water

• Understand the following terms: unsaturated zone or vadose zone, saturated zone or phreatic zone, water table, perched water table. The capillary fringe is the partially-saturated zone above the water table due to surface tension drawing water upwards. The water table generally follows the shape of the topography and is highest in the winter when evapo-transpiration from photosynthesis is lower. During the summer, plant growth lowers the water table by removing water from the soil.

• Understand the following terms: aquifer, aquitard, porosity, and permeability. Understand that a confined aquifer has aquitards above and below to prevent fluids from escaping, and an unconfined aquifer lacks an aquitard above the aquifer. What conditions are necessary for an artesian aquifer? Why does surface land subsidence occur following large-scale withdrawal of ground water?

• Know rock examples with high porosity and high permeability; low porosity and low permeability; high porosity and low permeability; and low porosity and high permeability.

• What season does the salt water wedge in a coastal river extend the furthest upstream and why? Which season does it extend the least distance upstream and why? Why is ground-water withdrawal from the Baton Rouge aquifers producing problems with salt water intrusion and with land subsidence? Why is the water table dropping within the Ogallala Formation in the HIgh Plains?

• What are the two ways that groundwater is heated before exiting the surface as a hot water spring or geyser? What causes superheated groundwater to flash to steam, producing a geyser?

• Travertine is the general term for a surface water deposit of calcium carbonate which always forms by degassing of ground water when it is exposed to the atmosphere, e.g., as in a spring. Petrified wood is composed of silicon dioxide, i.e., quartz or opal, deposited from ground water below the surface of the ground. Sinter and geyserite refer, respectively, to hot spring and geyser precipitates of quartz (silicon dioxide) from ground water exiting on the surface. Spelotherms (stalactites and stalagmites) and dripstone (travertine) are cave deposits of calcite (calcium carbonate) that form from degassing of carbon dioxide from ground water in caves. Remember that the source of carbon dioxide within ground water is from rain water picking up the carbon dioxide from the metabolism of bacteria in the soil zone and then subsequently moving downward to the water table.

• In coastal areas, if the water table is 3 feet above sea level, approximately how thick is the total fresh-water lens? What is meant by a cone of depression around a well?

• Where (in relation to the water table) do caves generally form? What causes the formation of stalagmites and stalactites? What surface rock results in karst topography? What are the general features of karst topography?

Review Topics for Chapter 18 - Deserts and Wind Action

• Where are the locations on the earth's surface that deserts' form and what are the reasons for their formation at those locations?

• What type of drainage and streams exist in desert regions? What do we mean by arroyos and alluvial fans and how do they form? What is the pediment surface? What are playas and how do they form?

• Undestand the difference in particle transport between a sandstorm and a dust storm? What are loess deposits? What are ventifacts and how do they form? What is meant by desert pavement and blowouts and how does deflation produce them?

• Wind deposits from sand storms produce sand dunes (with giant crossbeds) of which there are 4 major types. The downwind side of a dune is steep and is called the slip face. Barchan dunes have their horns pointing downwind and form in areas of limited amounts of sand. Transverse dunes form in regions with higher amounts of sand where the dunes run into each other so that the horns are obscured. Both barchan and transverse dunes require a constant wind direction. If the wind direction is variable over an agle of less than 90 degrees, longitudinal (seif) dunes form which can be parallel to the wind direction with slip faces on both sides of the dune. Parabolic dunes form in coastal beach areas where vegetation can anchor the horns of a dune down which causes them to point upwind. Star dunes form in areas where the wind direction is truly variable, 90 to 180 degrees.

Review Topics for Chapter 19 - Glaciers and Glaciation

• Understand why glaciers move and how they move? How fast do glaciers move? What direction does ice always move within a glacier? What are the different stages in the formation of glacier ice? What is meant by the firn or neve? What is the firn line? Where is the deformation in a glacier plastic and where is it brittle and how does a glacier move over bedrock. What causes rock flour and where do we find deposits of rock flour in Louisiana? How do striations form? What is meant by basal sliding of a glacier and what is meant by glacial plucking? Why do crevasses generally not reach deeper than 50 meters?

• When did the last Ice Age end? How far south did the ice sheets cover North America during the last Ice Age? Where is crustal rebound occurring from the melting of the ice during the last Ice Age? How much colder was the earth's surface durng the Ice Ages? What are some possible causes of the Ice Ages? Who was Milankovitch and what did he propose?

• What is meant by a valley glacier, an ice sheet, and an ice cap? Where do ice sheets occur today? What is an ice shelf and how will melting an ice shelf affect sea-level rise? If all the glaciers melt due to global warming, how high will sea level rise? If the Antarctic Ice Sheet slips into the South Atlantic Ocean, how high will sea level rise? How will the rise in sea level from global warming affect New Orleans and South Louisiana?

• Know how the following glacier landforms form: U-shaped valley, arete, cirque, horn, hanging valley, moraines (medial, lateral, ground, and terminal), kames, eskers, kettles, truncated spurs, drumlins, fiords, eratic, drop stones, and roche moutonnee. What is meant by drift, till, and tillite?

Review Topics for Chapter 20 - Waves, Beaches, and Coasts

• Understand wave height, wavelength, wave refraction, longshore drift, swish and swash, longshore current, rip currents, particle movement in ocean waves, why waves break as they approach the shoreline, the depth to which water in a wave moves under the surface.

• Typically, coasts overlying subduction zones are rising (emergent) and sinking along continental margins that lacking a plate boundary due to sediment deposition along the coast. Rising coasts commonly preserve old beaches where waves have eroded flat terraces which are now above the present sea level, e.g., along the west coast of the United States. Sinking coasts commonly have barrier islands, marshes, and lagoons, e.g., along the Gulf Coast and the east coast of the United States.

• Erosion occurs along a coast with sediment transport in the direction of the longshore drift. Groins, sea walls, breakwaters, jetties, and beach nourishment are used to control this erosion, usually with unintended results. Spits and bay mouth bars are deposited where the coast turns inland. Barrier islands form parallel to the shore due to offshore sand deposition when sea level drops or erosion of old deltas. Erosion features include arches, sea stacks, wave-cut platforms forming the bottom of a beach, wave-cut clifts, tombolo.

• Reefs are built of the shells of marine animals that coexist with plant-like organisms (in their tissue) which require light for photosynthesis. Hence they can live only in shallow water. Fringing reefs form in shallow water near a coast. As the coast sinks, the living coral builds on top of dead coral and stays near the surface, producing a barrier reef that is further separated from the coast. If the barrier reef surrounds an island, the reefs can become an atoll if the entire island sinks below the surface. This is how Pacific atolls form around sinking volcanic islands.

• Sediment is carried along the shore by longshore drift. The longshore drift along the Louisiana coast is to the west and explains the lack of nice beaches in Louisiana west of the Mississippi River delta. Most of the sediment in the Mississippi River delta is not carried back to the Louisiana coast to rebuild it because the present delta is being built too far out in too deep water.

• Why does the earth have two high tides and two low tides and why do the times of the tide change each day? What are spring tides and neap tides, when do they occur, and what causes them?

• Why is the Pacific US coast emergent and why are the Atlantic and Gulf coasts of the U.S. submergent?