1. SEAFLOOR SPREADING – YES!! 1.HOW DOES THIS RELATE TO THE FORMATION OF THE OCEAN FLOOR? 2.IS THE EARTH GETTING BIGGER? 3.HOW DOES THE FORMATION OF NEW OCEAN FLOOR RELATE TO THE DEFORMATION OF THE EARTH’S SURFACE?

3. Intrusive Mafic Igneous Rock -- Gabbro

5. Sequence of Crystallization Bowen’s Reaction Series More Dense Less Dense

6. ISOSTACY – REACHING A BALANCE IN DENSITY

10. Fig.4.05 DISTRIBUTION OF EARTHQUAKES ON EARTH AREAS OF SPREADING – AREAS OF CONVERGENCE

11. Fig.4.03 EARTH IS CONSTRUCTED OF SOLID TECTONIC PLATES

13. OCEAN-CONTINENT COVERGENCE

15. Driving Mechanisms Slab pull-Ridge push Ridge push – The higher elevation of the MOR pushes the adjacent lithosphere away. Slab-pull – Once an oceanic plate begins to subduct, it pulls the rest of the plate with it Plates may be slowed or hastened by convection in asthenosphere

16. Plate velocities may be determined by… –Assuming fixed hot spot locations –Measuring volcano age / distance along a hot spot track. Plate Velocities Plate velocities

18. Tectonic plates All plates move continuously relative to one other. - Motion ranges from 1 to 15 cm/yr Plates interact along boundaries -Divergent -Convergent -Transform Tectonic plates: Earth’s lithosphere is divided into ~20 plates

20. Three types of Convergent Margins

21. WHAT HAPPENS TO A PLATE WHEN IT SUBDUCTS?

22. Formation of Intermediate Composition Magmas Partial Melting and Crustal Rock Assimilation

23. Convergent Margins Cascades Sierra Nevada Mts. Central America Andesitic/Rhyolitic Volcanism

27. OCEAN-OCEAN COVERGENCE

29. Mt. Fuji Volcanic Activity at Ocean-Ocean Boundary

32. Accretion of Continents Through Accretion on the Margins

33. CONTINENT-CONTINENT COVERGENCE

34. MAJOR MOUNTAIN RANGES COMMONLY COINCIDE WITH THE MARGINS BETWEEN CONVERGENT PLATES

35. The Wilson Cycle

36. Fig. 13.20 W. W. Norton

37. Fig. 13.22 W. W. Norton

38. Palisades Sill: Rifting during Breakup of Pangea