Hazard Exploration #2—Getting to Know the Plate Boundaries: Attempt review

2/13/23 下午 11 : 32 Hazard Exploration #2—Getting to Know the Plate Boundaries: Attempt review 第 1/19 ⻚ https://ilearn.sfsu.edu/ay2223/mod/quiz/review.php ? attempt=405245&cmid=391443 My Courses / ERTH031004-S23R-5103 / Week 3—The Skinny on Plate Tectonics—due 21 February / Hazard Exploration #2—Getting to Know the Plate Boundaries Question 1 Correct Mark 1.00 out of 1.00 Question 2 Correct Mark 1.00 out of 1.00 Question 3 Correct Mark 1.00 out of 1.00 Started on Monday, 13 February 2023, 11:25 PM State Finished Completed on Monday, 13 February 2023, 11:31 PM Time taken 5 mins 44 secs Marks 24.00/24.00 Grade 100.00 out of 100.00 There is no substitute for watching this week’s video: Colliding Continents! It is an outstanding summary with tons of useful imagery and animations! For a link, please see this week’s study guide. Based on the estimates of Alfred Wegener (explained in the video) approximately when did the supercontinent called Pangea begin to split apart? Select one: a. ~430 million years ago b. ~350 million years ago c. ~200 million years ago  d. ~50 million years ago The Theory of Plate Tectonics is super powerful, because it explains ____________________. Select one: a. Milankovitch Cycles b. the global distribution of earthquakes c. the global distribution of volcanoes d. both a and b e. both b and c  Based on your reading, it is clear that evidence for plate tectonics comes from: Select one: a. Sonograms of the ocean floor b. Magnetic surveys of the ocean floor c. Volcanic chains that parallel the subduction zones d. Distributions of non-marine fossils across the globe e. All of the above 

2/13/23 下午 11 : 32 Hazard Exploration #2—Getting to Know the Plate Boundaries: Attempt review 第 2/19 ⻚ https://ilearn.sfsu.edu/ay2223/mod/quiz/review.php ? attempt=405245&cmid=391443 Question 4 Correct Mark 1.00 out of 1.00 The active volcanic setting at the mid-oceanic ridge, where new oceanic crust is being formed, is a hot and violent place. Colliding Continents shows video clips that give a view of this hostile place. Here is an oblique view of a mid-oceanic ridge: New oceanic crust is created by eruptions at the mid-oceanic ridge. It fundamentally consists of a volcanic rock called basalt. Eruptions of basaltic lava are occurring everyday underwater. Similar underwater basalt eruptions also happen on the big island of Hawaii. Basalt rock that solidifies in water is called pillow basalt because... lava balloons and pushes agains the water, then implodes a little when gases are released. Here is a spectacular video example: https://www.youtube.com/watch?v=xsJn8izcKtg&t=1s . Because of the high heat flow in this area, ground water boils and results in underwater geysers on the seafloor. These are called black smokers. Here is superb video footage of these phenomenon: https://youtu.be/KtFFmDGIsa4 The charged particles in lava orient themselves based on the direction of earth’s magnetic field. When the lava cools and hardens, the minerals inside freeze in that position, resulting in a permanent rock record of the magnetic field at that time. Because eruptions have created new oceanic crust at mid-oceanic ridges for at least hundreds of millions of years, the ocean floor provides a long record of shifts in earths magnetic field. Scientists discovered these magnetic changes on the ocean floor prior to witnessing the ridge itself. This new information was pivotal, because it gave geologists a sense for how oceanic crust forms! Check out your reading for details on magnetic reversals... or do a bit of online research. Evidence for past changes in the magnetic field (i.e., magnetic anomalies) were measured by ships equipped with geophysical sensors!

2/13/23 下午 11 : 32 Hazard Exploration #2—Getting to Know the Plate Boundaries: Attempt review 第 4/19 ⻚ https://ilearn.sfsu.edu/ay2223/mod/quiz/review.php ? attempt=405245&cmid=391443 Question 5 Correct Mark 1.00 out of 1.00 Question 6 Correct Mark 1.00 out of 1.00 Consider this map which shows the locations of global hotspots (orange dot) in relation to the major plate boundaries (shown as red and black lines #1-3) . Which of the following statements about hotspots is most true? Select one: a. Hotspots occur on plate boundaries b. Hotspots lie in a chain parallel to plate boundaries c. Hotspots occur randomly  d. Hotspots create islands e. Hotspots move over time. Consider the location of volcanos across the globe in relation to the position of the plate boundaries. Here is a map of the plate boundaries:

2/13/23 下午 11 : 32 Hazard Exploration #2—Getting to Know the Plate Boundaries: Attempt review 第 5/19 ⻚ https://ilearn.sfsu.edu/ay2223/mod/quiz/review.php ? attempt=405245&cmid=391443 Here is another map that shows the location of volcanos worldwide: The greatest number of volcanos tend to:

2/13/23 下午 11 : 32 Hazard Exploration #2—Getting to Know the Plate Boundaries: Attempt review 第 7/19 ⻚ https://ilearn.sfsu.edu/ay2223/mod/quiz/review.php ? attempt=405245&cmid=391443 Question 7 Correct Mark 1.00 out of 1.00 As we learned last week, the planet earth has di ff erent layers that can be mapped clearly. Your text and the Naked Science video show these nicely: https://youtu.be/6wxI5pCRvL0 Geologists identify these layers or zones using one of two di ff erent criteria—chemical di ff erences (mineral content) or physical strength (e.g., solid or liquid). Refer to your textbook's description of the lithosphere. Which of the statements below best describes the lithosphere? Select one: a. The lithosphere is the innermost solid layer consisting of iron and nickel. b. The lithosphere is a layer that consists of a hot crystal mush. c. The lithosphere is mostly solid rock that flows because it is hot. d. The lithosphere is mostly solid rock that is strong but brittle.  e. The lithosphere is a convecting liquid that generates earth’s magnetic field.

2/13/23 下午 11 : 32 Hazard Exploration #2—Getting to Know the Plate Boundaries: Attempt review 第 8/19 ⻚ https://ilearn.sfsu.edu/ay2223/mod/quiz/review.php ? attempt=405245&cmid=391443 Question 8 Correct Mark 1.00 out of 1.00 Question 9 Correct Mark 1.00 out of 1.00 Topography describes changes in the surface elevation of the land. As one drives eastward from the beach to the California coastal mountains and then to the central valley, one encounters changes in topography. Explore global patterns in topography, which you can play around with to your hearts content using this site: https://www.ldeo.columbia.edu/~small/GDEM.html . This map is similar to map that we explored in Hazard Exploration #1. This time, please open your text to the map of the plate boundaries, and compare these two maps. The mountain belts that are highest in elevation tend to be located along which type of plate boundary? Select one: a. divergent oceanic boundary (plates moving apart from each other) b. convergent boundary (plates moving toward each other)  c. divergent continental boundary (plates moving apart from each other) d. There is no association of mountain belts with plate boundary type. Below is a color map that shows di ff erences in seafloor age. The age of the oceanic lithosphere is indicated by color, according to the legend on the right. Note that the rocks that make up the continental lithosphere are not colored. Those rocks are generally much, much older than the ages shown in this range for oceanic lithosphere. Compare this map to the map of plate tectonic boundaries:

2/13/23 下午 11 : 32 Hazard Exploration #2—Getting to Know the Plate Boundaries: Attempt review 第 10/19 ⻚ https://ilearn.sfsu.edu/ay2223/mod/quiz/review.php ? attempt=405245&cmid=391443 Question 10 Correct Mark 1.00 out of 1.00 Question 11 Correct Mark 1.00 out of 1.00 Refer to the map of seafloor age below. Where in the oceans is the oldest ocean crust generally found? Select one: a. in an oceanic trench where it’s about to be subducted b. on the continental shelf at passive margins c. the abyssal plain in the deepest ocean d. near the mid-ocean ridges e. A and B  Why doesn’t radiometric dating of volcanic basalt rocks that make up the ocean floor provide us with an absolute age for the planet earth? Please choose the best answer. Select one: a. New oceanic crust is produced every day b. Black smokers alter the rock so radiometric dating is ine ff ective c. Spreading rates at mid-oceanic ridges are variable d. Oceanic crust is recycled too frequently at subduction zones  e. Mid-oceanic ridges move over time Your answer is correct.

2/13/23 下午 11 : 32 Hazard Exploration #2—Getting to Know the Plate Boundaries: Attempt review 第 11/19 ⻚ https://ilearn.sfsu.edu/ay2223/mod/quiz/review.php ? attempt=405245&cmid=391443 Question 12 Correct Mark 1.00 out of 1.00 Below is a diagram showing an earthquake occurring on a fault within the earth’s lithosphere. Because the view is oblique, we can see the location of the earthquake at depth below earth’s surface (called the focus). If we only observe the location of an earthquake on the earth's surface, shown as dot on a map called the epicenter, then we won’t know the depth at which the earthquake took place. The epicenter only gives the location in terms of north - south - east - west. Again, there is a di ff erence between an earthquake epicenter (point at the earth’s surface above an earthquake) and an earthquake focus, which shows depth . The focus is the point in 3D where the earthquake actually originates, usually in the lithosphere. Refer to the figures below showing: 1) The global distribution of tectonic plates and plate boundaries, and 2) The global distribution of earthquakes. The plot shows the location of the earthquake epicenters, but they are colored according to the depth of the earthquake focus! Thus the figure really provides information about the focus too! Which of the following statements is true? You may download the files shown below from the folder on iLearn to view the images in full size. These maps are also in your textbook.

2/13/23 下午 11 : 32 Hazard Exploration #2—Getting to Know the Plate Boundaries: Attempt review 第 13/19 ⻚ https://ilearn.sfsu.edu/ay2223/mod/quiz/review.php ? attempt=405245&cmid=391443 Question 13 Correct Mark 1.00 out of 1.00 a. Earthquakes only happen at tectonic plate boundaries. b. Earthquakes occur at great depths at divergent plate boundaries. c. Earthquakes mostly happen along tectonic plate boundaries.  d. Earthquakes along subduction zones are always shallow. e. Earthquakes only happen at hotspots. Your answer is correct. Below is a map of the major plate boundaries (several similar figures also appear in your text!) Consider the global earthquake distribution in relation to the location and type of plate boundary. Here, earthquakes are colored points. The location of the point is the location of the earthquake epicenter. In this figure, the depth of each earthquake is indicated by the color of the point. Use the explanation for the color di ff erences provided to the right of the figure to assess which earthquakes are relatively deep and which are relatively shallow. Along divergent plate boundaries, earthquakes tend to be:

2/13/23 下午 11 : 32 Hazard Exploration #2—Getting to Know the Plate Boundaries: Attempt review 第 14/19 ⻚ https://ilearn.sfsu.edu/ay2223/mod/quiz/review.php ? attempt=405245&cmid=391443 Select one: a. shallow  b. shallow to intermediate c. shallow to deep d. deep Your answer is correct.

2/13/23 下午 11 : 32 Hazard Exploration #2—Getting to Know the Plate Boundaries: Attempt review 第 16/19 ⻚ https://ilearn.sfsu.edu/ay2223/mod/quiz/review.php ? attempt=405245&cmid=391443 Question 16 Correct Mark 1.00 out of 1.00 Question 17 Correct Mark 1.00 out of 1.00 Question 18 Correct Mark 1.00 out of 1.00 Again, take a peek at the figure above, which shows the motion of individual plates, and if needed, review the info in the Overview. Compression is a force applied to an area... also called pressure or stress. This is similar to the pressure that is applied to your hand when someone squeezes your hand too hard! Which type of plate boundary is characterized by compressional stresses? Select one: a. divergent boundary b. convergent boundary (subduction type) c. convergent boundary (continental collision type) d. transform boundary e. A and B f. B and C  Shear is a force that you feel on the sides of your legs, when you slide into home base—low and slow. Which type of plate boundary is characterized by shear forces? Select one: a. divergent boundary b. convergent boundary (subduction type) c. convergent boundary (continental collision type) d. transform boundary  e. hotspot Take another peek at your plate tectonic map... What kind of continental margin do we live on here in San Francisco? This describes the familiar San Andreas fault! FYI, this is the single most important question that you will answer in the course all semester! Please remember the correct answer. :-) Select one: a. transform  b. oceanic divergent c. continent to continent convergent d. oceanic to continent convergent e. continental divergent

2/13/23 下午 11 : 32 Hazard Exploration #2—Getting to Know the Plate Boundaries: Attempt review 第 17/19 ⻚ https://ilearn.sfsu.edu/ay2223/mod/quiz/review.php ? attempt=405245&cmid=391443 Question 19 Correct Mark 1.00 out of 1.00 Question 20 Correct Mark 1.00 out of 1.00 Question 21 Correct Mark 1.00 out of 1.00 Now look over at the east coast on the plate tectonic boundary map... What kind of continental margin is the east coast of the United States? Select one: a. Active b. Passive  c. Marginal d. Atlanticus e. Pacificus What type of plate boundary is forming the Himalaya Mountains, the tallest above sea level in the world?? Select one: a. Continent to continent convergent  b. Divergent c. Ocean to continent convergent d. Ocean to ocean convergent e. Transform Your answer is correct. Plate tectonic processes lead to rapid formation (at oceanic ridges) and destruction (at subduction zones) of oceanic lithosphere... but the continental lithosphere (especially cratons!) is not recycled very quickly, in general. The Colliding Continents video shows footage of the oldest craton on earth and gives its age! Continental crust is generally ______________ than oceanic crust. Select one: a. older  b. denser c. thinner d. richer in iron and magnesium e. all of the above Your answer is correct.

2/13/23 下午 11 : 32 Hazard Exploration #2—Getting to Know the Plate Boundaries: Attempt review 第 19/19 ⻚ https://ilearn.sfsu.edu/ay2223/mod/quiz/review.php ? attempt=405245&cmid=391443 Question 24 Correct Mark 1.00 out of 1.00 Consider the location of Magnitude 8 and greater earthquakes since 1900 based on these resources: http://www.businessinsider.com/map-earthquakes-magnitude-animated-1900-2016-8 and http://www.livescience.com/30320-worlds-biggest-earthquakes-110412.html These are the largest earthquakes in history! There is a pattern in terms of what types of plate boundaries and faults are responsible for these events. You may find it helpful to compare the earthquake locations to the map of major plate boundaries... What type of plate boundary is known to create the most powerful earthquakes? Select one: a. divergent b. transform c. convergent  d. transverse e. hotspot Your answer is correct. ⾢ Skinny on Plate Tectonics Overview! Jump to... Students Speak Survey! :) ▶ San Francisco State University A California State University Campus Academic Technology