USU 1360 TECTONICS / PROCESSES

Transcription

1 USU 1360 TECTONICS / PROCESSES

2 Observe the world map and each enlargement Pacific Northwest Tibet South America Japan a1 South Atlantic Arabian Peninsula

3 Observe features near the Pacific Northwest Ridge Cascade volcanoes Step in seafloor a1

4 Observe features near South America Oceanic trench Andes Low-relief interior Continental shelf on east a1

5 Observe features of the South Atlantic Ocean Ridge Zigzags in ridge Fracture zones a1

6 Observe features near the Tibetan Plateau Himalaya Lowlands in India Tibetan Plateau a1

7 Observe features near Japan Curving ridges Oceanic trenches a1

8 Observe features near the Arabian Peninsula Persian Gulf Red Sea Afar region a1

9 Observe some of the main features on Earth s surface Oceanic fracture zones Continental shelves Plateaus Submerged ridges and island arcs Linear island and seamount chains Deep ocean trenches Continents Mid-ocean ridges Oceanic plateaus a1

10 Observe the pattern of earthquakes (yellow dots) EQ in belts Mid-ocean ridges Southern Eurasia Trenches Mountain belts Sparse in some regions a1

11 Observe the pattern of volcanoes (orange triangles) Belts Mid-ocean ridges (not all shown) Island arcs next to trenches Oceanic islands Red Sea and East Africa Mountain belts next to trenches Sparse in some regions b1

12 Observe the pattern of elevations (brown = high) Mountains in belts Southern Eurasia high Oceans vs. continents East Africa high Some mountain belts next to trenches Most of continents gentle and low b2

13 Compare the distribution of earthquakes (yellow), volcanoes (orange), and high elevations (brown) EQ, volcanism, or mountain building = tectonic activity Belts of tectonic activity divide lithosphere into tectonic plates a1

14 Three Types of Relative Plate Motions Move apart: divergent boundary Move toward each other: convergent boundary Move horizontally past one another: transform boundary b

15 Observe the locations of different types of plate boundaries Compare these locations with mid-ocean ridges, oceanic trenches, mountains belts, lines of islands, etc c1

16 Oceanic Divergent Boundaries Oceanic plates move apart at mid-ocean ridges (seafloor spreading) Forms new oceanic crust Mid-Atlantic Ridge a

17 Features and Processes of Mid-Ocean Ridges Narrow trough, or rift Ridge high (hot rocks and thin lithosphere) Magma erupts or solidifies at depth; forms new oceanic crust Asthenosphere rises and melts Magma rises through fractures Sketch a mid-ocean ridge, labeling the processes in your own words a1

18 Observe what happens when continents rift apart Initial uplift from rising mantle Stretching and faulting form rift (example: East African Rift) Melting forms magma Can lead to seafloor spreading and new ocean basin (example: Red Sea) Ocean widens with spreading (example: modern Atlantic) b

19 Ocean-Ocean Convergent Boundary Two oceanic plates move toward one another Trench and island arc One plate moves down = subduction a1

20 Features and Processes in Ocean-Ocean Convergence Trench Accretionary prism Eruptions form volcanic island arc Slab releases water Water causes melting of mantle Sketch ocean-ocean convergence, labeling the processes in your own words a1

21 Ocean-Continent Convergent Boundary Oceanic and continental plate converge Volcanoes and squeezing form mountain belt Trench Oceanic plate subducted beneath continent Overlying mantle melted Sketch ocean-continent convergence, labeling the processes in your own words b1

22 Observe the distribution of volcanoes around the Pacific Ring of Fire What do you think could explain the overall pattern? c1

23 Pacific Ring of Fire Oceanic plates subducted on both sides Spreading in East Pacific Rise Subduction beneath oceanic plates = island arcs (e.g., Japan) Subduction beneath continental plates = mountain belts with volcanoes (e.g., Andes) Explain the Pacific Ring of Fire, including why the west and east sides are different c2

24 Continent-Continent Convergence Two continents collide Subduction of oceanic part of plate Subduction brings continents closer Continents collide d

25 Continental collision = wide zone of deformation Pieces sliced off Thick crust = high elevation Few volcanoes Continental plate buoyant, so subduction ends Sketch a continental collision, labeling the processes in your own words d3

26 Transform Boundary Observe how these two plates are moving past each other Plates move horizontally past one another on transform boundaries Transforms link spreading segments in mid-ocean ridges Transforms link other types of plate boundaries a1

27 Observe the pattern of the Mid-Atlantic Ridge Spreading segments Transforms link spreading segments Sketch a transform boundary, labeling the processes in your own words a2

28 Observe plate boundaries near the west coast of North America (green lines are transform boundaries) b1

29 What Moves the Plates? Ridge push Slab pull Other forces, such as convection in mantle a1

30 Rates of Relative Plate Movement Plates move cm/year Some move faster than others Which plate boundaries have the fastest rates? b1

31 Geometry of Plate Boundaries Observe how the motion of these two plates varies as the boundary changes orientation Spreading along this orientation As boundary changes orientation, plates move horizontally past one another Transform boundaries link other types of plate boundaries, like two spreading centers or a spreading center with a subduction zone d1

32 Geometry of Plate Boundaries II Observe how the motion between the North American and Pacific plates varies as the boundary changes orientation As boundary bends, becomes convergent (Pacific plate subducted beneath NA) Transform boundary here (Queen Charlotte fault), with plates moving horizontally past one another d1

33 Test of Plate Tectonics Is Age of Seafloor and Thickness of Sediment Drill cores Sediment Volcanic rocks Volcanic rocks in crust youngest near ridge (just formed) Sediment thickens away from ridge (had more time to accumulate) a1

34 Formation of Linear Island and Seamount Chains Lines of islands and seamounts (e.g., Hawaii) Plate moves over a hot spot Plate subsides as cools, so islands become seamounts Volcanoes become inactive as area moves away from hot spot Volcano forms over a hot spot c

35 Why is South America Lopsided Observe the features around South America Envision a cross section from west of South America to the Mid- Atlantic Ridge a1

36 Compare this cross section with the one you envisioned Andes (mountains and volcanoes) over subduction zone, with trench offshore Spreading along mid-ocean ridge Subduction beneath western edge Eastern edge of continent not a plate boundary (passive margin) b1

37 Middle Mesozoic (140 m.y ago) Late Mesozoic (100 m.y ago) Evolution of South America Observe the evolution of South America, beginning with continental rifting away from South America Present c