01_The_Lithosphere_-_Map_Exploration_Activity

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Apr 3, 2024

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Name: _________________________________________ Per. ________ Date: ____________ The Earth as a System – The Lithosphere Sources for this lesson: Exploring Earth: An Introduction to Physical Geology , 2 nd Edition, by Jon P. Davidson, Walter E. Reed, and Paul M. Davis This Dynamic Earth: The Story of Plate Tectonics , by W. Jacquelyne Kious and Robert I. Tilling, USGS, https://pubs.usgs.gov/gip/dynamic/dynamic.html Learning goal : By understanding patterns and interactions in Earth’s lithosphere, hydrosphere, and atmosphere, we can anticipate local natural disasters, predict climate changes, and identify how human impacts on the environment in one region of the Earth can also impact other regions of the planet. Background Information Earth is the only place in the Solar System that is known to have active plate tectonics. Combined with the presence of abundant liquid water, this makes Earth a dynamic planet and, as far as we know, the only planet in our Solar System that supports life. Earth’s uniqueness can be appreciated by a simple comparison with our nearest planetary body: the Moon. Questions : 1) Make observations of the image of Earth and the image of the moon. Describe the 2-3 key differences. 2) Which observations of Earth indicate that Earth is a dynamic system relative to the moon?
The Moon has a lifeless surface, pockmarked with craters, most of which are the result of meteorite impacts over 3 billion years ago. (For reference, the Earth is 4.55 billion years old.) Earth’s surface, although probably affected by similar meteorite bombardment, is constantly changing. The distribution of continents, oceans, and mountain ranges change as Earth’s plates slowing move and interact with each other. In this lesson, you will learn how scientists came to understand the dynamics of Earth’s lithosphere. Earth is composed of three layers – crust , mantle , and core . The crust and mantle are made of rocky material and the core is largely composed of iron. Earth is also divided into layers based on strength. Earth’s outer shell is a strong layer, about 100 to 200 km thick, called the lithosphere . The lithosphere overlies a weaker layer called the asthenosphere . Temperatures increase with depth in the Earth, such that the asthenosphere is generally hotter than 1000°C. In most places the asthenosphere is not molten but is capable of flow. The lithospheric shell is formed from a number of fragments, or plates . The positions, shapes, and sizes of plates have changed through time. Rates of plate movement are as much as 10 cm per year. During the 20th century, a major scientific concept— Theory of Plate Tectonics —emerged to explain why and how these plates move about and interact. This theory has unified the study of the Earth and proven to be as relevant to the earth sciences as was the discovery of the structure of the atom to physics and chemistry, and as was the theory of evolution to the life sciences. Even though the plate tectonics theory is now widely accepted by the scientific community, some aspects of it are still being vigorously debated today. Question : 3) Identify 1-2 questions or curiosities you have related to plate tectonics or the Earth’s composition. ------------------------------------ Pause – Complete Oreo Cookie Plate Tectonics Activity ---------------------------------------------- Data Exploration Part 1: Mapping the Age of the Lithosphere Some of the first clues leading to the theory of plate tectonics came from research in the ocean basins. About two thirds of the Earth's surface lies beneath the oceans. Before the 19th century, the depths of the open ocean were largely a matter of speculation, and most people thought that the ocean floor was relatively flat and featureless. However, as early as the 16th century, a few intrepid navigators found that the open ocean can differ considerably in depth, by taking
soundings with hand lines showing that the ocean floor was not as flat as generally believed. Oceanic exploration during the next centuries dramatically improved our knowledge of the ocean floor. We now know that most of the geologic processes occurring on land are linked, directly or indirectly, to the dynamics of the ocean floor. "Modern" measurements of ocean depths greatly increased in the 19th century, when deep-sea line soundings (bathymetric surveys) were routinely made in the Atlantic and Caribbean. In 1855, a bathymetric chart published by U.S. Navy Lieutenant Matthew Maury revealed the first evidence of underwater mountains in the central Atlantic. Our picture of the ocean floor greatly sharpened after World War I (1914-18), when echo-sounding devices -- primitive sonar systems -- began to measure ocean depth by recording the time it took for a sound signal from the ship to bounce off the ocean floor and return. Time graphs of the returned signals revealed that the ocean floor was much more rugged than previously thought. Such echo-sounding measurements clearly demonstrated the continuity and roughness of the submarine mountain chain in the central Atlantic (later called the Mid-Atlantic Ridge) suggested by the earlier bathymetric measurements. Computer-generated detailed topographic map of a segment of the Mid-Oceanic Ridge. "Warm" colors (yellow to red) indicate the ridge rising above the seafloor, and the "cool" colors (green to blue) represent lower elevations. This image (at latitude 9° north) is of a small part of the East Pacific Rise. (Imagery courtesy of Stacey Tighe, University of Rhode Island.) Through international collaboration among scientists and organizations, we now have extensive data of the age of the oceanic plates that make up the ocean floor. By examining these data over the entirety of Earth’s surface, various patterns begin to stand out. In this activity, you will explore age of the sea floor data for yourself and make observations. For the following questions, examine Figure 2: The Age of the Ocean Floor Questions : 4) Focus your attention on the rainbow colors that indicate the age of the oceanic crust over Earth’s surface. Note the color-coded scale provided in the upper left region of the screen. Identify 2-3 observations from these data. 5) Shift your attention to the Atlantic Ocean. Describe what the data of the age of oceanic crust show in this region. 6) With your group, suggest a possible explanation for the observed patterns related to the age of the sea floor in the Atlantic Ocean. In your explanation, include a hypothesis about the movement of tectonic plates in this region. 7) Identity another region of the ocean floor that may have a similar movement of tectonic plates based on the data.
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