* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Lesson 15 - Seismology Earths Interior
Survey
Document related concepts
Schiehallion experiment wikipedia , lookup
Plate tectonics wikipedia , lookup
Spherical Earth wikipedia , lookup
History of geomagnetism wikipedia , lookup
History of Earth wikipedia , lookup
Magnetotellurics wikipedia , lookup
History of geology wikipedia , lookup
Seismometer wikipedia , lookup
Large igneous province wikipedia , lookup
Future of Earth wikipedia , lookup
Age of the Earth wikipedia , lookup
History of geodesy wikipedia , lookup
Transcript
Chapter 17: Earth’s interior (Part I ) Ch 17: Earth’s interior 1) How is it done? Why care? Ch 17: Earth’s interior 1) How is it done? Why care? seismology high-pressure/temperature lab experiments meteorite studies computer modeling studies of magma gravity and magnetism studies understand how: Earth formed what causes volcanoes plate tectonics 2) Probing Earth’s interior 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 earthquake happens (slip on a fault) seismic waves travel away from earthquake they carry info about material they travel through earthquakes make P-waves & S-waves seismologists use them to: locate earthquakes earlier lecture determine what deep Earth is made of today 2) Probing Earth’s interior The nature of seismic waves Seismic wave speeds: depend on material properties are faster in more rigid materials increase with increasing depth (from more pressure) P waves: compressional waves: are fastest vibrate material back/forth in direction wave travels S waves: shear waves: slower than P-waves vibrate material side-to-side in direction wave travels 2) Probing Earth’s interior The nature of seismic waves P waves always faster than S-waves “primary” “secondary” wave paths are “bent” when crossing from one material into another 2) Probing Earth’s interior The nature of seismic waves wave paths are “bent” when crossing from one material into another reflections refractions q4 q3 q2 q2 2) Probing Earth’s interior The nature of seismic waves wave paths are “bent” when going deeper in Earth higher pressure = higher wave speed 3) Seismic waves & Earth’s Interior Compositional layers crust 3-70 km thick mantle down to 2900 km depth core 2900-6370 km depth Mechanical layers layer lithosphere stiff/strong, asthenosphere soft/weak, depth 0-100 km 100-660 km 4) Discovering Earth’s major boundaries crust mantle core boundaries between layers 4) Discovering Earth’s major boundaries The Crust Thickness: ~ 30 km (continents) 3-15 km (oceanic) Composition: similar to granodiorite (continents) predominantly basalt (oceanic) 4) Discovering Earth’s major boundaries The “Moho” Boundary between the crust and mantle Discovered in 1909 by Andrija Mohorovicic 4) Discovering Earth’s major boundaries The Mantle upper mantle Over 82% of Earth’s volume lower mantle mantle upper mantle 0 - 670 km lower mantle 670-2900 km D” region 2600-2900 km 400 & 670 km depth “phase transitions” Material suddenly compresses to a more compact form D” 4) Discovering Earth’s major boundaries The core-mantle boundary Boundary between the mantle and core mantle Discovered in 1914 by Beno Gutenberg …how? core Core-mantle boundary S-wave shadow zone Core was discovered …from a “shadow zone” P-wave shadow zone 4) Discovering Earth’s major boundaries The inner core Boundary between the outer liquid and solid inner core Discovered in 1936 by Inge Lehman …how? mantle core Inner core 4) Discovering Earth’s major boundaries The inner core She discovered reflections of seismic waves