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1. Earth’s plates are the outer portion of Earth. 2. Earth’s plates are relatively thin compared to the size of Earth. The depths at which Earth’s layers are found suggest that the plates, the outer layer of Earth, are relatively thin compared to the size of Earth. Possible Data Evidentiary Phenomena Sense-making between evidentiary and primary phenomena Primary Phenomena Sub-idea Sub-Idea A: The solid outer portion of Earth consists of separate plates of almost entirely solid rock. A1 Plates abut other plates on all sides. There are no visible gaps between plates that are adjacent to each other. A2 The upper portions of some of Earth’s plates contain the continents and some seafloor beneath the oceans. A3 The rest of Earth’s plates do not include continental material but only the seafloor beneath the oceans, or portions of the seafloor beneath the oceans. A4 There are 10–12 major plates. Major plates are larger than some continents; plates can be thousands of kilometers across. Plates average 100 km thick, which is 1/60 of Earth’s radius. 3. Earth’s plates are almost entirely solid rock. 4. Plates abut other plates. There are 10–12 major tectonic plates. The pattern of geological features and events defines plate boundaries. Since there are no gaps between the plates, plates must abut other plates. The outline of the plates shows that there are 10–12 major plates. 4.1 Earthquake activity occurs in observable patterns. Depth measurements of Earth’s layers. 5. The upper portions of some of Earth’s plates contain the continents and some of the seafloor beneath the oceans. Some of Earth’s plates contain only portions of the seafloor beneath the oceans. Location of epicenters, correlated with location of plate boundaries. 4.2 Volcanic activity occurs in observable patterns. Location of volcanic activity, correlated with location of plate boundaries. 4.3 Mountain ranges occur in observable patterns Location of mountain ranges, correlated with location of plate boundaries. Primary Phenomena Sub-idea Sub-Idea C: The plates that make up Earth’s surface are not static, but are quite dynamic. C1 All of Earth’s plates move very slowly (on average a few centimeters per year). C1.1 Since the continents are a part of the plates, they move in the exact same way as the plate moves. C2 A plate’s size and/or shape can be changed over time. C2.1 An individual plate (and its continent if present) may split apart into two separate plates (and two separate continents); two plates with continents on each are sometimes pushed together and fused to form a larger plate (and larger continent). C3 The speed or direction of plate motion can change over time. C4 Plates are on top of solid rock. They do not float or move on molten rock or water. C5 Abutting plates either move away from each other, toward each other, or alongside each other. C6 When abutting plates move toward each other, one plate typically slides beneath the other. 1. Earth’s plates move. Evidentiary Phenomena Sense-making between evidentiary and primary phenomena Possible Data 2. Earth’s plates move relative to each other. Plates either move away from each other, toward each other, or alongside each other. 3. Earth’s plates move very slowly. Hot spots are nearly stationary and beneath the plates. Therefore, a chain of volcanoes in the middle of a plate suggests that plates are moving. Plates are solid rock. Moving, breaking solid The fact that the locations rock results in earthquakes. on different plates can Thus, the occurrence of move closer together or We know that the continents earthquakes at plate farther away from each are the top parts of plates. boundaries provides New rock is forming at the other indicates that plates The match of the coastlines evidence that the plates mid-ocean ridge and moving can move toward each away from the mid-ocean We know that the continents suggests that the continents are moving. other, away from each are the top parts of plates. were once joined at one ridge, suggesting that other, or alongside If we assume that the point (Pangaea). Then the plates are moving away each other. from each other. continents were joined at one plates must have moved in order for the continents to point (Pangaea), then the plates must have moved in be in their current locations. order for the continents to be in their current locations. 1.1 Chains of progressively older volcanoes are formed by hot spots. 1.2 The present-day continents look much different from Pangaea. Table or narrative description of age (absolute or relative) of island vs. distance from “fixed point” (e.g. hot spot). Map of island chain and hot spot with age (absolute or relative) of islands superimposed on map. Map of Pangaea and map of present-day continents. Map showing the progressive breakup of Pangaea. 1.3 The coastlines of some of the continents appear as if they fit together like jigsaw puzzle pieces. Present-day map of South America and Africa. 1.4 Earthquakes occur at plate boundaries. Distribution of earthquakes superimposed on a map of plate boundaries. 2.1 Two locations on different plates can move farther away from each other or closer together. Latitude and longitude data over time for two locations on different plates. Distance between two locations on different plates over time. 2.2 On a plate, the farther rocks are from a midocean ridge the older the rocks are. Table of data with age of rock and distance from mid-ocean ridge. Dividing the distance from the spreading center by the age of the rock suggests a rate of plate movement of a few centimeters per year. Models that allow students to collect data about age of “seafloor.” 3.3 New rock is formed at spreading centers, and rock becomes progressively older moving away from the spreading center. 3.2 GPS ground stations move a few centimeters per year. Distance in miles between New York and Paris over many years. Distance between ground stations on different plates over time. Map with age of rock and midocean ridge superimposed on ocean floor. 5. Earth’s plates can join/fuse together to form larger plates. Rift valleys suggest that continents, and therefore plates, are splitting now. Each of these evidentiary phenomena indicates that Earth’s plates move very slowly. 3.1 Plate motion typically is not easily perceptible. Map with age of rock and mid-ocean ridge superimposed on ocean floor. 4. Earth’s plates can split apart into two separate plates; if a continent is involved in the splitting, this can result in two separate continents. Table of data with age of rock and distance from spreading center. The evidence suggests that continents, and therefore plates, were once joined. Since they are no longer joined, they must have split apart. 4.1 Similar nonmarine fossils are found on separate plates. Location of similar nonmarine fossils on separate present-day continents. 4.2 Coastlines of present-day continents on different plates appear to fit like pieces of a jigsaw puzzle. 4.3 Similar landforms are found on separate plates. Presentday map of continents. Representations of present-day continents that can be moved or manipulated. Some mountain ranges suggest that plate motion caused continents to collide, mountains to form, and plates to fuse together. 4.4 Several continents are actively splitting apart right now. Location of similar rock types and/or landforms on separate presentday continents. 6. The speed or direction of plate motion can change over time. The formation of the Appalachian mountains by the collision of the North American and African plate and the subsequent formation of the Atlantic Ocean when those plates moved away from each other The fact that continents indicate that the direction of the are the top parts of plates and movement of plates can change. the speed of a plate can Some seismic waves change over time suggests Bends in volcanic pass through Earth’s island chains that that when plates move, interior until they hit formed above hot their speed can change. the liquid outer core, spots suggest that showing that the a plate has shifted rock directly beneath its direction of plates is solid. movement. 5.1. Some mountain ranges formed where continents on two plates collided. The increasing distance between two points on the same continent that is actively splitting. 7. Earth’s plates are on top of solid rock. 6.1 The speed of a plate can change over time. Different rock types within the same mountain range. 6.2 Some volcanic island chains have bends. Speed of plate movement over time. 6.3 The Appalachian mountains formed by the collision of two plates, and the Atlantic Ocean formed when those two plates moved away from each other. Aerial views of volcanic island chains. 7.1 Some seismic waves can travel only through solid rock. Rate of travel of s-waves through Earth’s layers. Sub-Idea F: Sub-idea F1 F2 F3 Primary Phenomena F4 1. Plates move away from each other resulting in specific features and events. Evidentiary Phenomena Sense-making between evidentiary and primary phenomena Possible Data Plate motion causes abutting plates to interact with one another along their boundaries resulting in observable geological features and events. Prominent and distinctive features on Earth’s surface include volcanoes, mountain ranges (volcanic & non-volcanic), deep ocean trenches, and mid-ocean ridges. Events are significant occurrences or happenings at a given place and time, such as earthquakes, volcanic eruptions, and mountain building. These geological features and events are most common at, or close to, the boundaries between two plates. F3.1. Volcanoes, mountain ranges, and earthquakes can also occur in areas that are not near plate boundaries. Appendix 1 - The specific events and features that result from the different types of plate interactions are detailed in Appendix 1. When Earth’s plates move away from each other, earthquakes, volcanic eruptions, volcanic mountain-building, and rifting can occur, and volcanoes and mid-ocean ridges and rift valleys occur as a result of plate interactions. 1.1 Earthquakes occur where plates move away from each other. Occurrence of epicenters correlated to the location of divergent plate boundaries. 1.2 Volcanic eruptions or volcanoes occur where plates move away from each other Occurrence of volcanic eruptions or location of volcanoes correlated to the location of divergent plate boundaries. 1.3 Midocean ridges form where plates move away from each other. Location of midocean ridges correlated to the location of divergent plate boundaries. 1.4 Rifting or rift valleys occurs/form where plates move away from each other. Occurrence of rifting or location of rift valleys correlated to the location of divergent plate boundaries. 2. Plates move toward each other resulting in specific features and events. When plates with continents at their adjacent edges move toward one another, earthquakes, non-volcanic mountain building, and non-volcanic mountain ranges occur/form as a result of plate interactions. 2.1 Earthquakes occur when plates with continents on each plate move toward each other. Occurrence of earthquakes correlated to the location of convergent boundaries where both plates have continents at their adjacent edges. 2.2 Nonvolcanic mountain ranges form when plates with continents on each plate move toward each other. Location of nonvolcanic mountain ranges correlated to the location of convergent plate boundaries where both plates have continents at their adjacent edges. 3. Plates move alongside each other resulting in earthquakes. When plates with no continents or a continent on the edge of only one of the plates move toward one another, earthquakes, volcanic eruptions, volcanic mountain building, volcanoes, volcanic mountain ranges/series of volcanic islands and deep-sea trenches occur/form as a result of plate interactions. 2.3 Earthquakes occur when plates with no continents or a continent on the edge of only one of the plates move toward each other. Occurrence of earthquakes correlated to the location of convergent plate boundaries with no continents or a continent on the adjacent edge of only one of the plates. 2.4 Volcanic eruptions or volcanoes occur/ form when plates with no continents or a continent on the edge of only one of the plates move toward each other. Occurrence of volcanic eruptions or the location of volcanoes correlated to the location of convergent plate boundaries with no continents or a continent on the adjacent edge of only one of the plates. 4. Geological features and events are most likely to occur at or close to the boundaries between Earth’s plates. They can also occur in areas that are not near Earth’s plate boundaries. 2.5 Volcanic mountainbuilding occurs when plates with no continents or a continent on the edge of only one of the plates move toward each other. Location of volcanic mountain-building correlated to the location of convergent plate boundaries with no continents or a continent on the adjacent edge of only one of the plates. When Earth’s plates move alongside each other, earthquakes can occur as a result of plate interactions. 2.6 Volcanic mountain ranges/ series of volcanic islands form when plates with no continents or a continent on the edge of only one of the plates move toward each other. Location of volcanic mountain ranges correlated to the location of convergent plate boundaries with no continents or a continent on the adjacent edge of only one of the plates. 2.7 Deep sea trenches form when plates with no continents or a continent on the edge of only one of the plates move toward each other. Geological features and events can occur far from the boundaries between Earth’s plates and occur for reasons other than plate interactions. Geological features and events are most common at, or close to, the boundaries between Earth’s plates and occur as a result of plate interactions. 3.1 Earthquakes occur where plates move alongside each other. Occurrence of deep sea trenches correlated to the location of convergent plate boundaries with no continents or a continent on the adjacent edge of only one of the plates. Occurrence of earthquakes correlated to the location of transform plate boundaries. 4.1 The distribution of most volcanic activity outlines the location of Earth’s plate boundaries. The location of volcanic activity correlated to the location of plate boundaries. 4.2 The distribution of most earthquake activity outlines the location of Earth’s plate boundaries. The location of earthquake activity correlated to the location of plate boundaries. 4.3 The distribution of some mountain ranges outline the location of Earth’s plate boundaries. The location of mountain ranges correlated to the location of plate boundaries. Sub-Idea H: Sub-idea H1 H2 Primary Phenomena H3 2. Old rock at the edges of Earth’s plates returns deep into Earth’s interior where one plate goes beneath another plate as they move toward one another. 1. New rock from Earth’s interior is continually added to the edges of Earth’s plates that are moving away from one another. Sense-making between evidentiary and primary phenomena Evidentiary Phenomena Possible Data The rock that makes up plates is slowly being formed at some plate boundaries and returned to Earth’s interior at other plate boundaries. This means that Earth is not changing in size. New rock from Earth’s interior is continually added to the edges of plates that are moving away from one another. Because addition of rock and movement occur simultaneously, no gaps form between the plates. Old rock goes back deep into Earth’s interior in places where one plate goes beneath another plate as they move towards one another. Appendix 2 - The specifics of what, where, and how rock is being recycled are detailed in Appendix 2. Volcanic eruptions at mid-ocean ridges provide evidence of plate material being added (some at the surface but most below the surface). This activity indicates that the youngest plate material is at the edges of Earth’s plates that are moving away from one another. Plate material is progressively older the farther it is from a spreading center. This pattern suggests that new plate material is continuously added at spreading centers. Volcanoes near the edge of a plate where two plates are moving toward each other suggest that small amounts of plate material are being melted. This plate material comes from part of a plate that has gone back into Earth’s interior (subducted). Volcanic eruptions at mid-ocean ridges provide evidence of plate material being added (some at the surface but most below the surface). This activity indicates that the youngest plate material is at the edges of Earth’s plates that are moving away from one another. Plate material is progressively older the farther it is from a spreading center. This pattern suggests that new plate material is continuously added at spreading centers. The pattern of magnetic stripes on either side of the ridge further suggests that new plate material is continuously added at spreading centers. 1.1 Volcanic eruptions occur along mid-ocean ridges. Occurrence of volcanic activity correlated to the location of midocean ridges. 1.2 Rocks are progressively older as you move away from a midocean ridge. Age of rock correlated to the distance from the midocean ridge. 1.3 Magnetic stripes are present in the rock of the ocean floor, indicating a similar pattern on both sides of a mid-ocean ridge. 2.1 Volcanoes occur near the edge of a plate where two plates are moving toward each other. Location of volcanoes correlated with the location of convergent plate boundaries with no continents or a continent on the adjacent edge of only one of the plates. Trenches suggest that part of a plate has gone back into Earth’s interior. The pattern of earthquakes within a plate outlines the downward path of the subducting plate. 2.2 There is a pattern of progressively deeper earthquakes at a plate boundary Latitude, longitude, and depth of earthquake foci at a subduction zone. 2.3 Deep-sea trenches sometimes occur at the edge of a plate where two plates are moving toward each other. Location of deep sea trenches correlated to the location of convergent plate boundaries with no continents or a continent on the adjacent edge of only one of the plates.