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# Unit 4 Earth's Systems and Resources ## Lesson 1: Plate Tectonics The Earth's Layers * **Lithosphere:** (hard crust) * **Asthenosphere:** (liquid upper mantle) * Cycles in circular convection currents * **Mesosphere:** (mostly hard lower mantle) **Tectonic Plate Theory:** * Firs...

# Unit 4 Earth's Systems and Resources ## Lesson 1: Plate Tectonics The Earth's Layers * **Lithosphere:** (hard crust) * **Asthenosphere:** (liquid upper mantle) * Cycles in circular convection currents * **Mesosphere:** (mostly hard lower mantle) **Tectonic Plate Theory:** * First proposed by Alfred Wegener in 1915. * The hard lithosphere is broken into 15 plates that float over the denser, molten asthenosphere. **Evidence for the Tectonic Plate Theory:** 1. **Continents fit together:** Like puzzle pieces (Pangea). 2. **Ancient fossils and rocks:** Found on continents far apart, suggesting they were once joined. (e.g., 200 million years ago) 3. **Earthquakes, tsunamis, volcanoes, mountains, and ridges:** Occur at plate boundaries. **Types of Crust:** * **Continental Crust:** Less dense * **Oceanic Crust:** More dense **Types of Plate Boundaries:** 1. **Convergent Plate Boundary:** Plates moving towards each other. * **Oceanic + Oceanic:** Subduction of the oldest crust, results in trenches and volcanoes. (e.g., Mariana Trench) * **Oceanic + Continental:** Oceanic crust subducts, results in volcanoes and mountains. * **Continental + Continental:** Mountains and earthquakes. (e.g., Himalayas, Mt. Everest) 2. **Hotspots:** Occur in weak spots in the Earth's lithosphere (not necessarily at plate boundaries). * **Magma Plumes:** Asthenosphere rising to the surface. * Creates island arcs and volcanoes (e.g., Hawaiian Islands) * Creates continental hotspots (e.g., Yellowstone National Park) **Diagram:** The document includes diagrams showing: * A diagram of the Earth's layers (crust, mantle, outer core, inner core). * A labeled map showing continental drift and the distributions of fossils and ancient rocks. * A diagram illustrating the different types of plate boundaries (convergent, divergent, transform). * A diagram depicting the process of plate movement and the creations of certain geological features.