Understanding Plate Tectonics: Mechanisms and Landforms

Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie This lab covers the mechanisms of plate tectonics and the resulting landforms and events we see and feel on Earth’s surface. At the end of this lab you should be able to: 1) Explain the theory of plate tectonics in your own words 2) Summarize the reasons for different plate boundary interactions and describe the resulting surface landforms and events. 3) Evaluate where on Earth’s surface we have plate boundaries and describe the processes happening at these boundaries. 4) Use current landforms on Earth’s surface to classify former plate boundaries. You should start by watching three videos on iCollege: Wegener and Continental Drift, Sea Floor Spreading Proof, and Plate Tectonics. The work your way through these questions, referring back to the videos as needed. Part 1: Plate Tectonics 1) In the above diagram, arrows denote the direction of movement of the crust and mantle, with numbers and letters above each boundary between plates. Name each numbered plate boundary, and what types of plates are involved. (15 pts) Name of the numbered plate boundary what types of plates are involved 1 Convergent Island Arc 2 Divergent Mid Oceanic Ridge 3 Convergent Continental Arc 4 Divergent Continental Rift by Hot Spot 5 Convergent Orogenic Mountain

Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie 2) Name the lettered bathymetric (sea-floor) features in the figure above that are created by plate tectonics (2 pts) A: Island Arc B: Mid Oceanic Ridge 3) Describe in your own words the following plate boundaries. Where on Earth would you expect to find an example of each boundary? (6 pts) Convergent: - A plate boundary that involves two plates moving towards each other - The Himalayas, Western Andes Divergent: - A plate boundary that involves two plates moving away from one another - Rio Grande Rif Transform: - A plate boundary where plates slide sideways past each other - San Andreas fault zone 4) Name two ways oceanic crust differs from continental crust? (2 pts) - Their composition as well as their thickness/density . 5) Thinking back to your igneous rock labs, what two elements might account for these differences? (2 pts) Silicon and Magnesium

Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie 6) Look at the above image and answer the following questions (hint: Ma means Mega- annum, or millions of years) a. Where is the oldest oceanic crust in the Atlantic? (1 pt) Near the Continental margins in the Abyssal Plains , 200 Ma old b. Where is the youngest oceanic crust in the Atlantic? (1 pt) Near Mid Atlantic Ridge, less than 10 Ma old c. Explain why this variation in the age of the oceanic crust exists across the Atlantic Ocean. (2 pts) Its due to the divergent boundary at the Mid-Atlantic Ridge. The new ocean crust is constructed at the MAR and the Divergent Boundary of the MAR moves it away from the MAR toward Continental margins, so as a result the newest crust is found at MAR whereas it gets older as we move towards Continents.

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Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie d. The feature in the middle of the Atlantic Ocean is called the Mid-Atlantic Ridge. Given your responses to the above questions, is this a convergent, divergent, or transform boundary? (1 pt) It is a Divergent boundary.

Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie

Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie Earthquakes distribution

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Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie 8) Using the above maps of volcanos and earthquakes, answer the following questions: a. Which of the following has high concentrations of volcanos? Mark all that apply. (4 pts) ___ Eastern Atlantic Ocean __-_ Eastern Pacific Ocean _-__ Hawaii ___ Western Atlantic Ocean __-_ Western Pacific Ocean ___ Iceland b. One of the oceans in the world is referred to as the “Ring of Fire” – which might it be and why? (4 pts) It’s the Pacific ocean because it contains a path of several active volcanos as well as earthquakes. c. Given your responses to the above questions, is a convergent, divergent, or transform boundary represented in locations that have volcanic activity and high concentrations of earthquakes? (2 pts) It’s a Convergent Boundary

Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie Part 2: Plate Tectonics and Landforms

Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie 12)Rocky Mountains The Rocky Mountains formed during the closure of the Cretaceous Interior Seaway, a shallow sea between North America and an archipelago in the Pacific Ocean. What kind of boundary is this? (2 pts) Convergent Boundary

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Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie 13) Jordan Valley and the Dead Sea The Jordan Valley in the Levant is composed of the Sea of Galilee, which flows into the Jordan River, and eventually into the super salty Dead Sea. This valley is at the boundary of the African and Arabian plates. The valley is composed of sediments that have eroded into the space between the two plates, and the valley is so deep that the Dead Sea is below sea level! What kind of boundary is this? (2 pts) Transform Boundary

Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie 14) The Ural Mountains The Ural Mountains in central Russia are some of the oldest mountains in the world. They are near no plate boundaries, no earthquake activity, and essentially in the middle of the Eurasian plate. Hypothesize how they formed, keep in mind from the Hawaii example in the lecture that plate movement can change over time. (4 pts) The Ural Mountains likely formed through the collision of ancient continental blocks during the assembly of supercontinents like Pangea or due to pas mountain-building events associated with compressional fears within Earth’s crust.

Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie 15) Lake Superior Lake Superior is an exceptionally deep lake north of Michigan’s Upper Peninsula. While the other Great Lakes are much shallower and are hypothesized to be formed from retreating glaciers at the end of the ice age, scientists suspect something different for Lake Superior. It should be noted that ages of the rocks in Isle Royale and the Keweenaw Peninsula (both colored

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Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie orange and green on the East side of the map) have mirrored ages in their rocks, getting older further away from each other. Hypothesize how Lake Superior formed (4 pts) Lake Superior’s formation resulted from a combination of geological processes and tectonic events. It likely began with continental rifing, creating a low-lying basin through stretching and faulting. Glacial activity and volcanic events in the Keweenaw Peninsula contributed to the lake’s basin shaping. Over time, erosion, sedimentation, and rock accumulation deepened the lake. 16) Mid Ocean Ridge You know that Mid Ocean Ridges are created from Divergent boundaries. However, you may have noticed that they only form straight lines for a while and are quite jagged. This is the result of trying to split apart curved surfaces. This implies another

Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie kind of fault is also at play here. If the crust is spreading away from each of the green lines, which other fault type/boundary is present here? (1 pt) Transform Fault

Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie 17) Iceland The island of Iceland in the North Atlantic is formed from a hot spot/mantle plume just the same as Hawaii. However, we don’t see an island chain, only a singular large island. Why might this be? (4 pt) Iceland’s formation, like Hawaii’s is linked to a hotspot or mantle plume. However, the key distinction lies in their geological settings. While Hawaii, located in middle of the Pacific Plate, results in an island chain as the plate moves over the hotspot, Iceland is at the boundary of Eurasian and North American Plates, where the Mid-Atlantic Ridge serves as a divergent plate boundary. As these plates pull apart, magma continuously wells up to fill the gap, creating a singular, large island along the length of the boundary. This leads to the formation of a single island in Iceland, despite the presence of a hotspot.

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Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie Part 3: Seismic Explorer Go to the following website to complete the final activity: https://seismic-explorer.concord.org/ Click “Map Type” and choose “Relief”. Click “Data Type” and have both “Plate Boundaries” and “Earthquakes” enabled Hit “Start” in the lower left. This will show major earthquakes over time. Answer the following questions: 1. What patterns in the locations of earthquakes do you observe? (1 pt) They tend to form on the natural fault lines of earth 2. Red dots are shallow earthquakes while blue dots are deeper. What areas of the world have blue dots? What plate boundaries are these? (2 pts) South America and Eastern Asia, The South American Plate and the Philippine Plate Click “Draw Cross Section” in the lower right. Draw a cross section with it covering part of western South America with both red and blue dots, going from red (P1) to blue (P2). Then click “Open 3D View” in the lower right. 3. Describe the relationship (trend) between depth of earthquakes and distance from plate boundary. (1 pt) The earthquakes are significantly deeper when they occur closer to the plate boundary Close the 3D view and cancel cross section drawing. In “Data Type” enable “Plate Movement” and “Plate Names” and disable “Earthquakes”. Each “i” if clicked on will show the speed of movement and boundary name (e.g., “COC-NAZ”). 4. Click around these “i”’s. Which plate boundary in the Pacific Ocean is moving the fastest? (2 pts) PAC-NAZ

Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie 5. Even this fast plate above doesn’t have uniform speed or direction across all its boundaries. Hypothesize why below. Keep in mind all plates are moving independently of each other and all speeds are relative to the opposing plate. (2 pts) The plate might not be able to move at uniform speeds across all boundaries due to obstacles and friction that can redirect movement and cause variations in speed and direction Part 4: Summary Fill in the below chart to summarize your understanding of characteristics at different plate boundaries. (10 pts) TYPE DESCRIBE MOVEMENT CRUST Created? Destroyed? Neither? EARTHQUAKES? Shallow? and/or Deep? TYPE OF VOLCANISM? Rifting? Volcanos? WHERE IN WORLD? (EXAMPLES) Divergent Apart Created Shallow Rifting Rio Grande Rift Convergent Under/Over Destroyed deep Volcanoes Pacific Northwest

Lab 7 – Plate tectonics GEOL 1121 Name Yonatan Nigussie (Subduction) Transform Slide past Neither Shallow None

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Lab 7 -PlateTectonics_activity (1)

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