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Seismic Waves Standard 8-3.2 Explain how scientists use seismic waves & Earth’s magnetic field to determine the internal structure of Earth. Seismic Wave Behaviors EQ: 8-3.2 • How do primary, secondary, and surface waves behave as they travel through the Earth? Earthquake Waves • What are the 3 types of seismic waves? • Primary (P) Waves (longitudinal) • Secondary (S) Waves (transverse) • Surface Waves Primary Waves • move out from the • How do primary earthquake focus waves behave • travel the fastest as they travel • move through solid & through the liquid layers of Earth Earth? • push & pull rock • back-and-forth motion in the direction the wave is moving Secondary Waves • How do secondary waves behave as they travel through the Earth? • move out from the earthquake focus • move slower than primary waves • move through solid rock only • move at right angles to primary waves causing rocks to move up & down & side to side Surface Waves • How do surface • form when P and S waves reach the waves behave surface as they travel through the • cause the ground to Earth? shake • make rock sway from side to side & roll like an ocean wave Earth’s Internal Structure: Seismic Waves EQ 8-3.2: How do scientists use seismic waves to determine the internal structure of Earth? Inside Earth • Seismic Waves: • scientists look at their speed & direction to infer what’s inside of the Earth. • Ex.) Primary waves slow down when they reach liquid, & speed up when they go through solids. • These wave behaviors • liquid outer core b/c waves slow down cause us to infer what solid inner core b/c about the Earth’s core? waves speed up • How do we know the mantle is denser than the crust? • earthquake waves travel faster through the mantle Earth’s Internal Structure: Magnetic Field EQ 8-3.2: How do scientists use Earth’s magnetic field to determine the internal structure of Earth? Inside Earth: Magnetic Field • What is inferred to be the cause of Earth’s magnetic field? • the movement of materials in the outer core of Earth • Why are iron and nickel • they are 2 easily inferred to be in Earth’s magnetized metals core? • How will a compass • it will align (line up) with needle behave within the lines of force of Earth’s magnetic field? Earth’s magnetic field Cause and Effect 1. Cause/Density crust: less dense mantle: more dense Effect/Speed slower seismic waves faster seismic waves 2. Cause outer core spins Effect Earth’s magnetic field 3. Cause iron & nickel easily magnetize Effect inferred to be in Earth’s core