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History of Earth 1
NYS Earth & Space Sciences
| Term | Definition |
|---|---|
| Alfred Wegener's Continental Drift | The hypothesis that continents were once joined together in a supercontinent called Pangaea and have since drifted apart to their current positions. Though initially rejected, this theory laid the groundwork for modern plate tectonic theory. |
| Fossil Evidence | Identical fossils of plants and animals found on continents now separated by vast oceans, such as the Mesosaurus reptile found in both South America and Africa. This evidence supported Wegener's idea that continents were once connected. |
| Rock Evidence | Similar rock formations, mountain ranges, and geological structures found on different continents that match when the continents are fitted together, such as the Appalachian Mountains in North America aligning with mountains in Europe and Africa. |
| Modern Evidence of Plate Tectonics | Current scientific proof supporting the movement of Earth's crustal plates, including seafloor spreading, earthquake patterns, volcanic activity distribution, GPS measurements showing continental movement, and paleomagnetic data from ocean floor rocks. |
| Magnetic Polarity Reversals | Periodic changes in Earth's magnetic field where the magnetic north and south poles switch positions. Creates a striped pattern of magnetic orientations on the ocean floor that provides evidence for seafloor spreading. |
| Mid-Atlantic (Ocean) Ridge | A divergent tectonic plate boundary running down the center of the Atlantic Ocean where new oceanic crust is formed through volcanic activity. This underwater mountain range demonstrates seafloor spreading and continental drift. |
| Ocean Trench | Deep, narrow depressions in the ocean floor formed where one tectonic plate subducts (slides) beneath another at convergent boundaries. These are the deepest parts of Earth's surface, such as the Mariana Trench in the Pacific Ocean. |
| Convergent Boundary | A type of plate boundary where two tectonic plates move toward each other and collide. Depending on the types of plates involved, this can result in subduction, mountain building, or volcanic activity. |
| Surface Features (Convergent) | Geological formations created at convergent boundaries including mountain ranges (like the Himalayas), volcanic arcs, ocean trenches, and earthquake zones where plates collide and compress. |
| Divergent Boundary | A type of plate boundary where two tectonic plates move away from each other, allowing magma to rise and create new crust. Most divergent boundaries occur along mid-ocean ridges. |
| Surface Features (Divergent) | Geological formations created at divergent boundaries including mid-ocean ridges, rift valleys (like the East African Rift), volcanic activity, and new oceanic crust formation through seafloor spreading. |
| Transform Boundary | A type of plate boundary where two tectonic plates slide past each other horizontally without creating or destroying crust. The San Andreas Fault in California is a well-known example of this boundary type. |
| Layers of Earth's Interior | The distinct zones within Earth based on composition and physical properties, including the crust (outermost solid layer), mantle (hot, flowing rock layer), outer core (liquid iron and nickel), and inner core (solid iron and nickel). |
| Oceanic Crust | The thin, dense layer of Earth's crust that forms the ocean floor, composed primarily of basaltic rock. It is typically 5-10 kilometers thick and is constantly being created at mid-ocean ridges and destroyed at subduction zones. |
| Continental Crust | The thick, less dense layer of Earth's crust that forms the continents, composed primarily of granitic rock. It is typically 30-70 kilometers thick and is older and more buoyant than oceanic crust, allowing continents to "float" higher on the mantle. |
| Plate tectonics | The unifying theory that explains the movement of Earth's lithospheric plates and their role in shaping Earth's surface features. |
| Continental crust | The thick, less dense portion of Earth's crust that forms the continents and can be over 4 billion years old. |
| Oceanic crust | The thin, dense portion of Earth's crust that underlies the ocean basins and is typically less than 200 million years old. |
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