Volcanic Rock

1. Volcanic Rock read pages 252-256 restate & answer Topic Questions 1-6 Chapter 14 Earth Science Book Essay # 4

2. Topic 1: Page 253 Earth Textbook Magma Molten Rock Underground Lava: Molten Rock on the Surface Volcano: Where Magma erupts as Lava

3. Earth’s layers can be classified based on composition. • Crust • 1% of Earth’s volume • oceanic crust • mostly basalt • continental crust • mostly granite • Mantle • 83% of Earth’s volume • mainly silicon and oxygen • Core • 16% of Earth’s volume • mainly iron (90%) and nickel http://www.llnl.gov/str/JulAug04/gifs/Fried1.jpg

4. Earth’s layers can also be classified by physical properties. • Lithosphere • cool, rigid • Athenosphere • hot, partially melted Lower mantle • Core • outer core • liquid • inner core • solid • 6,600oC!

5. Topic 1: Page 253 Earth Textbook FELSIC: High concentrations of SILICA. Light in color, Light in density. Can contain trapped gasses. Associated with explosive volcanic eruptions. MAFIC: High concentrations of Iron & Magnesium. Dark in color. Heavier in density. Gasses are not usually present. Associated with non-explosive eruptions Magma

6. Felsic or Mafic? Which is which? How do you know?

7. Felsic: Light overall color Mafic: Dark overall color Felsic or Mafic? Which is which? How do you know?

8. FELSIC & MAFIC ROCKS

9. Igneous Rock Identification Felsic Granite, Rhyolite, Obsidian, Pummice High in Si + O Low in Fe + Mg Mostly feldspar & quartz Light-colored Mafic (Gabbro, Basalt, Scoria) “Low” in Si + O High in Fe + Mg no quartz, abundant ferromagnesian minerals Dark colored Intermediate (Diorite)

10. Volcanoes • Volcanoes are the result of hot spots within the crust or mantle of the earth. • The hot, liquid rock will break through weak spots in the surface and form volcanoes or flood basalts. • Many volcanoes do not release lava, instead they spit ash and small bits of lava called lapilli. • Some eruptions are quiet with very fluid (low viscosity) lava flows while others are explosive

11. Pacific Ring of Fire Volcanism is mostly focused at plate margins

12. Topic 6: Page 256 Earth Textbook Subduction Eruptions *occur at subduction boundaries *erupt violently with gasses *usually contain felsic magma

13. Trench

14. Volcanoes Mt. St. Helen before the explosive eruption

15. Volcanoes

16. Volcanoes Mt. St. Helen after the eruption

17. Volcanoes

18. Volcanoes

19. Topic 5: Page 256 Earth Textbook Rift Eruptions *occur at spreading centers *erupt as slow flows with few gasses *usually contain mafic magma

20. Ridge

21. - Subduction - Rifting - Hotspots Volcanoes are formed by:

22. Volcanoes Quiet lava flows

23. Flood basalts

24. Volcanoes

25. Flood basalts Basalt is a type of rock that is produced from the mantle

26. Volcano locations

27. What are Hotspot Volcanoes? • Hot mantle plumes breaching the surface in the middle of a tectonic plate The Hawaiian island chain are examples of hotspot volcanoes. Photo: Tom Pfeiffer / www.volcanodiscovery.com

28. Pacific Ring of Fire Hotspot volcanoes

29. The tectonic plate moves over a fixed hotspot forming a chain of volcanoes. The volcanoes get younger from one end to the other.

30. Mid-Plate Hotspots

31. Hotspot

32. Mid-Plate Hotspots

33. Mid-Plate Hotspots

34. Volcanoes Shield

35. Earthquakes read pages 270-273 restate & answer Topic Questions 1-4 Chapter 15 Earth Science Book Essay # 5

36. Topic 1: Page 271 Earth Textbook What is an Earthquake? * over a million a year on Earth shaking of the Earth’s crust caused by a release of energy. Movement of lithospheric plates * one every 30 seconds

37. Topic 2: Page 271 Earth Textbook Causes of Earthquakes *eruption on a volcano *collapse of a cavern *impact of a meteor *Major Cause is the release of stress between two lithospheric plates.

38. Topic 2: Page 271 Earth Textbook Causes of Earthquakes *Major Cause is the release of stress between two lithospheric plates. * Elastic Rebound Theory - Overtime plates move, friction holds plates until they release and suddenly snap back into place

39. Topic 3: Page 272 Earth Textbook Depth of Earthquakes * Spreading centers/sliding boundaries tend to be shallow – less than 30 km depends on the type of plate boundary * Subduction boundaries however plunge to depths of 700km down

40. Topic 3: Page 272 Earth Textbook Earthquake Terms * Focus – the point on the fault plane where movement occurs * Epicenter – the point on the surface directly above the focus Diagram on page 272

41. Earthquakes

42. Topic 4: Page 273 Earth Textbook Earthquake Waves The speed of a wave depends on the material they are passing through The more dense the material the faster the wave travels (dominoes closer together – faster) P waves, S waves, L waves

43. Topic 4: Page 273 Earth Textbook Earthquake Waves * primary wave, fastest wave * compressional wave, like sound P waves * material moves back and forth * travels through solid liquid & gas

44. Topic 4: Page 273 Earth Textbook Earthquake Waves * secondary wave, slower than P * shear wave S waves * material moves side to side * travels through solids only

45. Topic 4: Page 273 Earth Textbook Earthquake Waves * Love wave, slowest wave * surface wave L waves * material moves like ripples on pond * travels through solid liquid & gas

47. Earthquakes generate seismic waves. Seismic waves travel through Earth and along its surface. • Seismic waves form in two types: • surface waves • sometimes seen as an wavelike motion in the ground • cause most of the property damage in an earthquake • 2) body waves (P and S waves) • useful for analyzing Earth’s interior structure http://ja.wikipedia.org/wiki/%E7%94%BB%E5%83%8F:Pswaves.jpg

48. Body waves 1) P (primary) wave • a compressional wave • similar to a sound wave • pass through liquids and solids http://www.met.gov.pk/Subpage4/waves_files/pwave_web.jpg 2) S (secondary) wave • a shear wave • like a rope shaken side to side • pass through solids only • about 1/2 the speed of P waves http://www.geo.uib.no/jordskjelv/img/s-wave.jpg

49. seismograph

50. P waves are faster than S waves About 3.5 km/sec About 6 km/sec