6.1+Earth's+Dynamic+Interior+.pptx
Transcript
HMH Science Dimensions Earth and Space Science Unit 6: Plate Tectonics Lesson 1: Earth's Dynamic Interior Unit 6 Lesson 1 Evidence of Structure and Composition • The crust of Earth’s continents has an average thickness of about 35 km. • It is more than 60 km thick in the Andes Mountains and more...
HMH Science Dimensions Earth and Space Science Unit 6: Plate Tectonics Lesson 1: Earth's Dynamic Interior Unit 6 Lesson 1 Evidence of Structure and Composition • The crust of Earth’s continents has an average thickness of about 35 km. • It is more than 60 km thick in the Andes Mountains and more than 70 km thick in the Himalaya Mountains. • The crust below the ocean is much thinner, averaging about 7 km. 2 Unit 6 Lesson 1 Evidence of Structure and Composition At 12 261 meters deep, the Kola Superdeep Borehole in northwestern Russia is the deepest borehole on Earth EXPLAIN Why haven’t scientists collected samples from Earth’s core? 3 Unit 6 Lesson 1 Evidence of Structure and Composition • Earth’s compositional layers—crust, mantle, and core—are distinguished by their chemical composition, the minerals and rock they are made of. 4 • Earth’s structural layers - lithosphere, asthenosphere, mesosphere, outer core, inner core are distinguished by physical properties, such as temperature, physical state, and whether the Unit 6 Lesson 1 Evidence of Structure and Composition • The outermost compositional layer of Earth is the crust. • The crust and part of the mantle below make up the Earth’s outermost structural layer, the lithosphere. • Seismic waves are waves caused by earthquakes. These waves reflect off boundaries and refract—change speed and direction—when they move from one material into another. 5 Unit 6 Lesson 1 Evidence of Structure and Composition About 83% of Earth’s volume is in the middle compositional layer of Earth known as the mantle. • The mantle is denser than the crust because it is made of a higher proportion of heavier elements, and it is compressed by the weight of the rock above. • The mantle can be divided into three structural layers based on its physical properties. The main 6 part of the mantle, just above the core, is called Unit 6 Lesson 1 Evidence of Structure and Composition • We know where the Moho is because there is a strong refraction of seismic waves in this zone. • Because the velocity of the waves decreases suddenly, scientists infer that the lithosphere ends and the next-lower layer, the asthenosphere, begins. • From this evidence, scientists infer that rock in the asthenosphere is not rigid, but is plastic, or very bendable like putty or clay, and is close to the melting point. 7 Unit 6 Lesson 1 Evidence of Structure and Composition Data Analysis This graph shows the velocity of P-waves (Vp) and S-waves (Vs) with depth and density. Explore the data.ays to radio frequencies. 8 Describe and compare the velocities of P- and S-waves with depth in Earth’s mantle. What do the gradual changes show? What do the sudden changes show? Unit 6 Lesson 1 Evidence of Structure and Composition • Many stony meteorites are similar to rock on Earth’s crust but appear to be unchanged since they formed 4.56 billion years ago. • Scientists think that iron meteorites are broken pieces of the cores of small bodies. 9 Unit 6 Lesson 1 Evidence of Structure and Composition • There is no direct evidence for the composition and physical properties of Earth’s core, the central part of Earth below the mantle; also the center of the sun. • Seismic data show that there are two internal layers: an outer core that is liquid and an inner core that is solid. 10 Unit 6 Lesson 1 Evidence of Structure and Composition The aurora borealis, also called the northern lights. In a compass, a needleshaped magnet aligns itself to Earth’s magnetic poles, ANALYZE Look carefully at the two images. What do they tell us about Earth’s interior? 11 Unit 6 Lesson 1 Earth’s Dynamic Interior • The flow of the solid rock of the mantle is driven by differences in density, which are caused by differences in temperature. • Convection occurs in the mantle at a rate of a few centimeters per year. 12 • Convection brings hot material up from the mantle toward Earth’s surface, where it may melt and erupt, forming volcanoes. Unit 6 Lesson 1 Earth’s Dynamic Interior The aurora occurs near the poles because Earth’s magnetic field traps and channels the particles toward the poles. 13 Unit 6 Lesson 1 Continue Your Exploration Choose one of the paths below to continue your exploration: • Seismic Tomography • Interiors of Other Worlds • Modeling Earthquake Waves 14 Unit 6 Lesson 1 Can You Explain It? In your analysis, address these questions: How would you evaluate the validity of Halley's model? What evidence supports both Halley's model and today's model? What evidence does not support the model of hollow spheres in Earth's interior? (If you have difficulty addressing this question, ask yourself: How might the evidence be different if Halley's model were correct?) 15
