1. Chapter 17: Earth’s interior (Part I )

2. Ch 17: Earth’s interior 1) How is it done? Why care?

3. Ch 17: Earth’s interior 1) How is it done? Why care?  seismology  high-pressure/temperature lab experiments lab experiments  meteorite studies  computer modeling  studies of magma  gravity and magnetism studies  seismology  high-pressure/temperature lab experiments  meteorite  meteorite studies  computer  computer modeling  studies  studies of magma  gravity  gravity and magnetism studies  understand how: Earth formed  what causes volcanoes  plate tectonics  understand  understand how: Earth formed  what  what causes volcanoes  plate  plate tectonics

4.  earthquake happens (slip on a fault)  seismic waves travel away from earthquake  they carry info about material they travel through 2) Probing Earth’s interior

5.  earthquakes make P-waves & S-waves  seismologists use them to: è locate earthquakes è determine what deep Earth is made of earlier lecture today  earthquake happens (slip on a fault)  seismic waves travel away from earthquake  they carry info about material they travel through  earthquake happens (slip on a fault)  seismic waves travel away from earthquake  they carry info about material they travel through

6. 2) Probing Earth’s interior  The nature of seismic waves è depend on material properties è are faster in more rigid materials è increase with increasing depth (from more pressure) Seismic wave speeds: P waves: è compressional waves: are fastest è vibrate material back/forth in direction wave travels S waves: è shear waves: slower than P-waves è vibrate material side-to-side in direction wave travels

7. 2) Probing Earth’s interior  The nature of seismic waves è P waves always faster than S-waves “primary” “secondary” è wave paths are “bent” when crossing from one material into another

8. 2) Probing Earth’s interior  The nature of seismic waves è wave paths are “bent” when crossing from one material into another

10.      reflectionsrefractions 

11. 2) Probing Earth’s interior  The nature of seismic waves è wave paths are “bent” when going deeper in Earth è higher pressure = higher wave speed

12. F Compositional layers F Mechanical layers 3) Seismic waves & Earth’s Interior crust 3-70 km thick mantle down to 2900 km depth core 2900-6370 km depth lithosphere stiff/strong, 0-100 km asthenosphere soft/weak, 100-660 km layer depth

13. F crust F mantle F core 4) Discovering Earth’s major boundaries boundaries between layers

14. F The Crust 4) Discovering Earth’s major boundaries Thickness: ~ 30 km (continents) 3-15 km (oceanic) Composition: similar to granodiorite (continents) predominantly basalt (oceanic)

15. F The “Moho” 4) Discovering Earth’s major boundaries Boundary between the crust and mantle Discovered in 1909 by Andrija Mohorovicic

16. F The Mantle 4) Discovering Earth’s major boundaries Over 82% of Earth’s volume upper mantle 0 - 670 km lower mantle 670-2900 km D” region 2600-2900 km mantle D” upper mantle lower mantle 400 & 670 km depth “phase transitions” 400 670 Material suddenly compresses to a more compact form

17. F The core-mantle boundary 4) Discovering Earth’s major boundaries Boundary between the mantle and core Discovered in 1914 by Beno Gutenberg mantle core Core-mantleboundary …how?

18. Core was discovered …from a “shadow zone” S-wave shadow zone

19. P-wave shadow zone

20. F The inner core 4) Discovering Earth’s major boundaries Boundary between the outer liquid and solid inner core Discovered in 1936 by Inge Lehman mantle core Inner core …how?

21. F The inner core 4) Discovering Earth’s major boundaries She discovered reflections of seismic waves