Forces of Change Day 3

Earth’s Structure Think of the Earth as a hardboiled egg Core—center of earth, very hot and solid; inner core made of iron and nickel under extreme pressure Mantle—located next to the outer core, thick layer of hot, dense rock Crust—outer layer; rocky shell forming the earth’s surface Underneath the continents and oceans is a CRUST, underneath the whole crust is a warmer layer called the mantle, underneath that is the hot inner core in the center Think of the Earth as a hardboiled egg Thin brittle shell  Crust that humans live on White, soft inside  Deep hot magma beneath the surface Yellow, yolk beneath  Core of the earth

Plate Movement 500 million years ago—Supercontinent Pangaea Continental Drift—Continents have slowly drifted apart Plate Tectonics Plates moving have produced Earth’s largest features Continents, mountains, and oceans Plates are crashing and spreading (but veryyy slowly) Crust is actually broken into pieces or PLATES, it’s not just one, there’s many pieces Pieces and plates actually move

Remember: Think about the plates as a hard boiled egg shell Notice anything similar about the arrows? What are different Have them notice that some are pointing toward and some are pointing away Remember: Think about the plates as a hard boiled egg shell

What happens when plates meet? Two important types of plate movements Divergent Convergent Which one do you think matches the images below? Convergent Divergent

Divergent Plate Movement Movement of plates in opposite direction Spreading Process (step by step) Sea plates pull apart—most happen in the ocean Results in a rift (deep crack) Magma from within the earth comes up between the plates Magma hardens and builds new oceanic crust

Examples: Mid Atlantic Ridge and East African Rift Valley (Divergent Plates) Snorkling at Mid Atlantic Ridge--https://www.youtube.com/watch?v=ZgywK-pQMp4 Underwater gorges (valley between mountains) caused by the spreading process

Convergent Plate Movement Two plates coming together Subduction Heavier sea plate dives under the lighter continental plate Crust starts to melt, returns to surface as volcanoes Example: Andes Mountain range in South America ******If new crust is created (through spreading), then it must be destroyed some where, otherwise the Earth would grow, which it cannot. Crust is consumed in subduction zones. Two plates can be two oceanic plates coming together, two continental, or combination of both Lithosphere—rigid outer part of the earth, consisting of the crust and upper mantel (it is two different plates) Asthenosphere—upper mantle of the earth, layer of solid rock that has so much pressure and heat the rocks so they can flow like a liquid. This allows the tectonic plates in the lithosphere to move around on the earth’s surface by floating on the rocks that are slowing flowing like a liquid

How are volcanoes formed? Subduction causes volcanoes How a Volcano is formed: (step by step) Two plates meet (convergent plate movement) One plate dives underneath Plate partially melts (in the upper mantle it is very hot) Makes magma that drills up to the top

How are Earthquakes formed? Violent movements of tectonic plates—pull, push, or slide How Earthquake is formed: (step by step) Two plates meet and create a fault line Massive pressure here Intense pressure causes the fault lines to give way Plates move over, against, or apart from each other Earthquake happens Waves of escaping energy radiate outward from the fault line Waves reach earth’s surface and shake the ground https://www.youtube.com/watch?v=FIgksa3x11w&list=PLat8Jejmdx1sa0MOWmvZ_f3Z-IeOZmtRv&index=29 Making science fun with crackers and cheese

Earthquake Diagrams

External Forces of Change How the Earth’s surface changes—Weathering and Erosion Step one: breaking down of rocks (weathering) Step two: rocks are carried away (erosion) Wind erosion—movement of dust, sand and soil from one place to another Glacial—as they move, they pick up rocks and soil in their paths; change landscapes, destroy forests, carve out valleys, alter course of rivers, and wear down mountains Glaciers, when they melt, leave behind large piles of rocks and debris that may sometimes form dams Water Erosion--Leftover sediment acts as sandpaper and grinds the surface of the rock

Water Erosion—Case study Grand Canyon Shaped by the Colorado River and widened by side streams For the past millions and millions of years! Weathering—wears away exposed surfaces over time Rocks will crumble if water seeps into cracks Erosion Water carries away the rocks fragments and shapes the canyon http://channel.nationalgeographic.com/videos/the-grand-canyon-story/ http://www.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.canyon/the-grand-canyon-how-it-formed/

Knowledge Check Weathering: the _____________________ _______________ of rock on the Earth’s surface Erosion: The ___________________ _________ of particles of sediment Answers: Weathering—breaking down Erosion: carrying away