Lab 10 plate tectonics

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Dec 6, 2023

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Geography 101 Plate tectonics Geography 101 Lab 10 Plate Tectonics Introduction: In 1912 German geophysicist and meteorologist Alfred Wegener publicly presented in a lecture, his idea that Earth’s large landmasses migrate. His book called, The Origins of Continents and Oceans, appeared in 1915. Wegener today is regarded as the father of this concept called continental drift. Wegener postulated that all landmasses were united in one supercontinent approximately 225 million years ago, during the Triassic period. This one landmass he called Pangaea, meaning all Earth. His proposal launched a half-century debate leading up to the adoption of plate tectonics as an all-encompassing theory of continental drift, sea floor spreading and subduction. Aided by an avalanche of discoveries, the theory today is nearly universally accepted as an accurate model of the way Earth’s surface evolves, and virtually all Earth scientists accept the fact that lithospherical masses move about. The Breakup of Pangaea: The figure below gives you the opportunity to work with an updated version of Wegener’s Pangaea, 225 to 200 million years ago (Triassic-Jurassic periods). Areas of North America, North Africa, the Middle East, and Eurasia were near the equator and therefore were covered by plentiful vegetation. The landmasses focused near the South Pole and attached to the sides of Antarctica were covered with ice. We also see that Africa shared a common connection with both North and South America. The Appalachians and the Atlas Mountains of North America and Africa reflect this common ancestry; they are in fact, portions of the same mountain range. The Atlantic Ocean did not exist. The only oceans were Panthalassa, which would become the Pacific and the Tethys Sea which eventually formed the Mediterranean Sea, with trapped portions becoming the present-day Caspian Sea. The figure above shows Pangaea as it was 200 to 225 million years ago. Alfred Wegener used paleoclimatic evidence to support his idea of plate tectonics. For example, there were tropical regions that have since been glaciated, while mid-latitude areas were once tropical swamps. For this section, you will identify locations that had very different climates in the past. For this assignment we will assume that we are looking at Permian conditions, when global temperatures were similar to current temperatures. You will have to estimate climate and biome locations using latitude (it is in 10-degree increments on the map above) and continentality to compare them to present climatic locations. For example, Northern India was located at roughly 35 S latitude and on the east coast of a large land mass. A location with a similar climate today would be China which has a humid subtropical climate. This is how the Earth continents are located today (latitude and longitude lines are in 20-degree increments. Please number the latitude and longitude lines on the maps above and below. 1

Geography 101 Plate tectonics This is how the Earth continents are located today World Climates and their guidelines Questions: Refer to the world maps above to answer the following questions. This will likely be easiest if you print in color and have the maps next to each other rather than having to scroll up and down. 1. For b – e below, write the letter on the map of Pangaea in the appropriate location. The first location is done for you as an example. Use the maps of the world climates and the current configuration of the globe to assist you. The first one is completed and there is a dot on the map of Pangaea on the continent of Africa. That dot is in the tropical rainforest today but on the map of Pangea it was located at about 30 S (desert ). a. A location that was a desert (under subtropical high), but is now a rainforest (tropical) - eastern coast of South America b. A location that would have been glaciated (arctic or Antarctic), but is now tropical - the South Pole c. A location that was tropical but is now in the mid-latitudes 2

Geography 101 Plate tectonics - the United States d. A location that was a rainforest, but is now a desert - the western coast of South America e. A location that would have been glaciated but is now arid - near the North Pole f. A location that has changed location the least - the center of Pangaea 2. To visualize the mechanisms that drive Earth’s lithospheric plates, refer to the figure below. a. At the time of Pangaea, South America and Africa were attached forming a continuous landmass. Explain the process(es) that likely transpired over the past 225 million years to position the two continents where they are today. - The Atlantic basin was created when the seafloor stretched apart, tearing the two continents apart in the process. b. With respect to the movement of crustal plates in the vicinity of the Andes Mountains: What is the oceanic plate diving beneath South America? How is this related to formation of the Andes? (The diagram below and the tectonic plate map under #3 may be helpful) - The top plate is forced upward when the plate beneath it dives, and mountains are created, which is how the Andes formed. - Nazaca plate 3. The figure below shows the tectonic features in modern times. A spreading center extends down the center of the Atlantic and into the southern Indian Ocean. Subduction trenches are active along the west coasts of Central and South America and throughout the western Pacific Ocean basin. The northern reaches of the India plate (pictured below as the northern part of the Indo- Australian plate) have under thrust the southern mass of Asia through subduction, forming the Himalayas in the upheaval created by the collision. Of all the major plates, India traveled the furthest. From approximately 150 million years ago until the present according to Robert Dietz and John Holden, more than half the ocean floor was renewed. The inset blocks (below the map) demonstrate the types of specific plate boundaries. a. Using the figure below, locate the following and determine what type of plate boundary they are (convergent, divergent, or transform). 1. On the ocean floor south of Alaska - Transform plate boundary 3

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