Lab - Plate Tectonics - 2022(1)

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Arkansas Tech University *

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2024

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Geology

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Feb 20, 2024

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PLATE TECTONICS Name: ________________________ For this lab you will be using Google Earth Browser or Desktop Application and files to add layers that possess data of geological significance called .kmzs. The .kmz is made available to you on Blackboard under the Plate Tectonics Lab content folder. Some elements from this lab you may recognize from Physical Geology, but they are early on. To operate Google Earth Browser and import .kmz files please watch the pre-recorded video that I made for Physical Geology lab that uses these tools. The videos can be found in Blackboard. Make sure to pay attention to what layer should be turned on to answer certain questions (in bold). Questions may be difficult to interpret on their own if you do not read and digest the prompts preceding them. You will also be using the USGS website to obtain real-time earthquake data. Google Earth can give us a map-view of Earth’s surface, and earthquakes can give us information as to what is underneath the surface. Recall that earthquakes are derived from rocks that undergo significant stress and break, releasing seismic waves. Earthquake information Scaling information Shallow-focus: < 70 km 1 in = 2.54 cm or 0.083 ft 1 cm = 10 mm Intermediate-focus: > 70 km; < 300 km 1 m = 3.3 ft 1 m = 100 cm Deep-focus: > 300 km 1 mi = 5280 ft or 1.6 km 1000 m = 1 km Time scale for the Age of Earth Crust layer: Questions 1) Download and open the Historical Geology Plate Tectonics .kmz file. Activate the Age of Earth Crust layer. Where on Earth is the plate boundary that separates the South American and African plates? Hint: You will have to move the globe around and use the key to determine what symbols divide plates. 2) If the boundary was not shown with any Google Earth Information, how would you determine the location of the boundary? Give two examples. Hint: What ocean or land geographic features would you look for?

3) Follow the link: USGS real-time earthquake map and click on the “gear” icon (upper right). Click the 30 days Magnitude 2.5+ and scroll down and choose the Satellite map layer. Notice that Plate boundaries are already present for you. Data for earthquakes can be attained by clicking on the dot that represents the epicenter of a particular earthquake. Where do most of the earthquakes in the Atlantic Ocean occur? Are they shallow or deep? Hint: Click a circle, which represents an earthquake epicenter, to find these data. 4) Activate the Age of Earth Lithosphere.kmz file. (Give it time to load all the pretty colors!) Considering oceanic plates: What age ranges do “warm” colors represent? What age ranges do “cooler” colors represent? Describe how the seafloor age changes from the plate boundary in the Atlantic Ocean towards the east coast of South America. 5) You can hover your cursor over the globe in Google Earth Browser and find elevation in the lower right-hand corner of the screen (you will have to zoom for this feature to activate). If you drag your cursor slowly across the screen you can see how elevation changes. Describe the relationship between seafloor age, bathymetry (seafloor topography), and the South American–African plate boundary. 6) Draw a profile (side view) of the South American–African plate boundary with plate motion arrows on each plate.

7) What type of boundary did you draw in question 6? How is new crust being produced here? 8) Focus on the Tonga-Kermadec plate boundary at the Tonga Trench. Describe how the ocean depth changes East to West as you approach and cross the Tonga–Kermadec plate boundary. Hint: To locate where this boundary is, type “Tonga Trench” in the Google Earth search field in the upper left corner of the screen. You will probably have to turn off the Age of Earth Lithosphere layer by unchecking it in the left-hand panel. 9) Use the USGS real-time earthquake map to study the distribution and depths of earthquakes around Tonga–Kermadec plate boundary. Select a few that compose the band of earthquakes parallel to the trench/boundary. What is the depth of the focus of these earthquakes? Why do you think earthquakes occur at these depths? 10) Activate the Volcanoes of the World .kmz in Google Earth. Describe the distribution of the volcanoes and how they relate to the Tonga–Kermadec plate boundary.

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11) Draw a profile across the Tonga–Kermadec plate boundary that synthesizes information you gathered from the ocean depth, earthquake, and volcano data. Include plate motion arrows and other clues to what is going on. Hint: You will have to draw a side view of the plate boundary that depicts more than what Google Earth shows at the surface. 12) What type of boundary is the Tonga–Kermadec plate boundary? Be as specific as you can. 13) Search for the Nazca–South American plate boundary by searching for “Nazca”. Google Earth will fly you to Nazca in South America. Just to the west is the plate boundary. If that marks the eastern boundary of the Nazca plate (Hint: it is only an oceanic plate), where is the western boundary? What type of boundary is at each location? 14) After identifying both boundaries of the Nazca plate. Zoom out and determine the types of boundaries you see surrounding the Pacific Ocean. Based on all the information you collected for the plate boundaries in the Atlantic and Pacific oceans earlier in this assignment, what do you think will happen to the Pacific Ocean in a couple hundred million years?

15) The Journal of Science calls the impending result “Amasia” a portmanteau of “America” and “Asia”. Does this match your response from Question 14? Come up with a more interesting name to call it! 16) Now, we will focus on the remnants of a once larger Farallon Plate called the Juan de Fuca Plate. Use the ruler tool again to measure the distance from the trench to the volcanoes on Google Earth Browser. Be sure to set your units to kilometers. Use this to represent the different coasts of western North America as listed below. Fill in data for Trench–to–Volcano distances across the two plate boundaries: - Aleutian Islands, Alaska: __________ km - Northwest Coast of United States: __________ km 17) Rocks undergo partial melting with the introduction of volatiles from subduction at an average depth of 110 km. We will use that average depth to compare descent angles of plates. Based on the profile you drew in question 11 and data you derived earlier in the assignment, indicate what each field on the right triangle below would represent. Use: trench-to-volcano distance, partial melting depth, subducting slab, and angle of descent. Rank the descent angles of the same locations based on steepness using “more” and “less”. - Aleutian Islands, Alaska: __________ steep - Northwest Coast of United States: __________ steep

18) Describe the trend that data from question 16, and diagram and results from question 17 depict. Hint: Complete the following statement: The greater the trench-to-volcano distance the descent angle of the subducting slab is________ 19) You already know what distance from a spreading center means in relation to the age of oceanic crust. Find the distance from divergent boundary of the oceanic plate to the trench where it is subducted for each of the locations. - Aleutian Islands, Alaska: __________ km - Northwest Coast of United States: __________ km Summary 20) One major trend from your findings from questions 16–19 is what? Hint: it should relate to age of oceanic lithosphere. 21a) What is the average age of the oldest oceanic crust? Hint: Use the Age of Earth Lithosphere .kmz. 21b) The age of the oldest continental crust is 4.0 Ga (billion years old), why is this so much older than the oldest oceanic crust?

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Lab - Plate Tectonics - 2022(1)

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