Alfred Wegener, early 1900s

1

• Alfred Wegener, early 1900s
• Proposes continental drift to explain alignment
  of coastlines and rocks / fossil assemblages
  across the Atlantic.
• Hypothesis rejected as preposterous, What does a
  meteorologist know anyway?

2
Fig. 2-1, p.13
3
Fig. 3.14
4
Fig. 3.13
5
review of crust, mantle, lithosphere,
asthenosphere Env. Fig 3.4 Haz fig 2-8
6
Fig. 1.03
7
(No Transcript)
8
Fig. 2-10, p.18
9
Fig. 2-13, p.20
10
Fig. 3.04
11
Fig. 2-11, p.19
12

• World seismicity and volcanism defined sets of
  plates (1960s).
• Env fig 4.5 like Env. 3.5 Haz 2-16, 2-17

13
Fig. 3.05
14
Fig. 4.05
15
Fig. 2-16b, p.22
16
Fig. 2-17, p.23
17
Fig. 3.06
18
Plate Tectonic System is an open system with
energy exchanged but not mass, i.e a cycle
(called the Tuzo-Wilson cycle). Env 3.22 gt
Haz 2-8 --Energy exchange is part of Earths
heat transfer system --Cycle is driven by
convection AND density contrasts (gravitys
response to heat-induced uplift) --Density
contrasts due to heat, but also composition.
19
Fig. 2-8, p.17
20
Fig. 3.22
21

• I. Plate Margins (Env fig 3.6)
• A. Divergent margin
• 1. Ocean-Ocean crust (Haz 2-19)
• 2. Ocean-Continent crust?
• 3. Continent-Continent crust?

22
Fig. 2-15, p.21
23

• I. Plate Margins (Env fig 3.6)
• A. Divergent margin
• 1. Ocean-Ocean crust (Haz 2-19)
• Rifting and Evidence for It
• 2. Ocean-Continent crust?
• 3. Continent-Continent crust?

24
Fig. 2-19, p.25
25
Evidence for rifting

• 1) Magnetic anomalies (Env fig 3.9), (Env 3.8 gt
  Haz 2-4) Haz 2-6
• 2) Sea Floor Ages (Env fig 3.10) see also Haz
  2-5 (ship), 2-7 (map)

26
Fig. 3.08
27
Fig. 2-4, p.15
28
Fig. 3.09
29
Fig. 2-6b, p.15
30
Fig. 2-5, p.15
31
Fig. 2-6, p.15
32
Fig. 2-6a, p.15
33
Evidence for rifting

• 1) Magnetic anomalies (Env fig 3.9), (Env 3.8 gt
  Haz 2-4) Haz 2-6
• 2) Sea Floor Ages (Env fig 3.10) see also Haz
  2-5 (ship), 2-7 (map)
• Single most astounding fact although the
  continents have rocks in excess of 3 b.y., no
  ocean crust is older than about 275 m.y. !!!

34
Fig. 3.10
35

• I. Plate Margins (Env fig 3.6)
• A. Divergent margin
• 1. Ocean-Ocean crust
• Already discussed above.
• 2. Ocean-Continent crust? 3.
  Continent-Continent crust?

36

• I. Plate Margins (Env fig 3.6)
• A. Divergent margin
• 1. Ocean-Ocean crust (Haz 2-19)
• 2. Ocean-Continent crust?
• Well sort of Back-arc spreading is near
  continent, but technically this is ocean-ocean
  (see B2 Haz 2-24b)
• 3. Continent-Continent crust?

37
Fig. 2-24b, p.26
38
Fig. 3.18
39

• I. Plate Margins (Env fig 3.6)
• A. Divergent margin
• 1. Ocean-Ocean crust (Haz 2-19)
• 2. Ocean-Continent crust? 3.
  Continent-Continent crust?
• Rifting intiates in continent, but if rifting
  is complete, it becomes ocean-ocean crust.

40
Fig. 2-23, p.26
41
Fig. 2-21, p.25
42

• I. Plate Margins (Env fig 3.6)
• B. Convergent margin
• 1. Ocean-Continent crust
• ex. South American subduction zone
• 2. Ocean-Ocean crust
• 3. Continent-Continent crust

43
Fig. 2-24a, p.26
44
Fig. 3.18
45

• I. Plate Margins (Env fig 3.6)
• B. Convergent margin
• 1. Ocean-Continent crust
• 2. Ocean-Ocean crust
• ex. Japan Island Arc Subduction Zone
• 3. Continent-Continent crust

46
Fig. 2-24b, p.26
47
Fig. 3.18
48

• I. Plate Margins (Env fig 3.6)
• B. Convergent margin
• 1. Ocean-Continent crust
• 2. Ocean-Ocean crust
• 3. Continent-Continent crust
• ex. Himalayas

49
Fig. 2-27, p.28
50
Fig. 3.19
51
Fig. 2-29, p.28
52
Fig. 2-28, p.28
53
Fig. 2-30, p.29
54
Fig. 2-30a, p.29
55
Fig. 2-30b, p.29
56
Fig. 2-30c, p.29
57

• I. Plate Margins (Env fig 3.6)
• C. Transform margin connect rift zones
• 1. Almost all are Ocean-Ocean crust,
  separating ocean rifts on sea floor, but
• 2. Ocean-Continent crust (San Andreas)
  and
• 3. Continent-Continent crust (Anatolia Fault
  Zone, Turkey)
• are most infamous.

58
Fig. 3.16
59
Fig. 2-31, p.29
60
Fig. 2-18, p.24
61
II. Continental Margins

• Active Margins are plate margins with associated
  tectonic activity.
• Passive margins are NOT plate margins.
• Continental margins are NOT the same as plate
  margins, though active continental margins fall
  into one of the plate margin categories
  near-divergent (i.e. back-arc), convergent, or
  transform.

62
III. Did a Rift Subduct?

• Hypothesis by Tanya Atwater

63
Fig. 2-18, p.24
64
Fig. 2-21, p.25
65
Fig. 2-20, p.25
66
Fig. 2-26, p.27
67
IV Other Evidence

• Hot Spot Tracks
• --Hawaii
• --Yellowstone

68
Fig. 3.20
69
Fig. 2-36, p.32
70
IV Other Evidence

• Triple Junctions
• East African Rift Aulacogen
• Mendocino Triple Junction

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Fig. 2-22, p.26
72
Fig. 3.17
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Fig. 2-18, p.24
74

• The Rock Cycle in the context of Plate Tectonics

75
Fig. 2.13
76
Fig. 3.23