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Tectonic Plates Tectonic Plates The LITHOSPHERE, or Earth’s outer layer, is broken up into huge pieces plates tectonic __________. called _________ –These plates are continuously moving ________. Let’s look at pg. 396 Answer this question… How do we know so much about the mantle and the core? – Seismic waves, or vibrations produced from earthquakes, travel at different speeds through the Earth. Their speed depends on the density and composition of the material they pass through. – Traveling through a solid will go faster than through a liquid. Restless Continents Look at pg. 400! Alfred Wegener In the early 1900s, ___________ ___________ continental wrote about his hypothesis of ____________ drift ______. continents once Continental drift = the _____________ landmass formed a single ______________, then broke up, and drifted to their current locations. fossils Continental drift also explained why __________ of the same plant and animal species are found on continents that are on different sides of the Atlantic Ocean. Pangaea Wegener thought that all of the present continents were once joined __________ in a single, huge continent called Pangaea ______________. Pangaea is Greek for “all earth” ______________. Events caused by Earth’s plate movement: 1. Sea-floor spreading 2. Mountain building 3. Earthquakes 4. Volcanoes Mountain Building Mountains ______________ exist because tectonic plates are continually moving colliding ______________ and ___________ with one another. Compression tension ________________ or ____________ can form mountains in several ways. 3 types of mountains: 1. Folded Mountains: squeezed --Form when rock layers are _______________ upward together and pushed ___________. --Example: Appalachian Mountains 2. Fault-Block Mountains: --Form when tectonic forces put ___________on the Earth’s crust causing tension drop down large blocks to_________ _________. --Example: Tetons in Wyoming 3. Volcanic Mountainsmagma --Form when _________ rises to the Earth’s surface and erupts. – Example: Mount St. Helens Earthquakes Most earthquakes take place near the edges of tectonic plates __________ ___________. As tectonic plates push, pull, or slip past each other, stress increases along breaks in the Earth’s faults crust, or ___________. In response to this stress, rock in the plates deforms _______________. Elastic deformation __________ _______________: Imagine a stretched rubber band. You can only stretch rock so far before it breaks. When the rock breaks, it energy releases ________________. Sea-Floor Spreading Process by which new oceanic ________________ forms as __________ lithosphere magma rises toward the surface and solidifies. mid-ocean ridges Occurs at ____________ __________, or underwater mountain chains tectonic plates As ___________ __________ move away from each other, the sea floor spreads apart and magma fills the gap. Look at page 402… Figure 3: Sea-Floor Spreading Volcanoes tectonic ______ plate _________. boundaries Likely to form at _________ The Ring of Fire ________ _________ _____ _________, plate boundaries surrounding the Pacific Ocean, 75% of the world’s active contains nearly _____ volcanoes. 80% of active volcanoes on land form About _____ 15% collide where plates ______________, and about ______ separate form where plates ____________. At these plate boundaries it is possible for magma _____________ to form and travel to the surface. The Ring of Fire 3 Types of Boundaries… Look at pg. 404-405 1. Convergent Boundaries: --Formed when two tectonic plates __________ COLLIDE a. Continental-Continental Collisions b. Continental-Oceanic Collisions c. Oceanic-Oceanic Collisions 2. Divergent Boundaries: --Formed when two tectonic plates SEPARATE ____________ 3. Transform Boundaries: --Formed when two tectonic plates SLIDE past each other horizontally ________