Download presentation
Presentation is loading. Please wait.
1
Intermission: Intermission: Plate Tectonics
2
National Oceanic and atmospheric Administration/National Geophysical Data Center
3
Alfred Wegener
4
Evidence: (1) Continents Fit Together
5
Evidence: (2) Rocks & Structures Match Up
8
Evidence: (3) Glacial Features
10
Evidence: (4) Fossils
11
Pangea
12
Animation Link
13
“If we are to believe Wegener’s Hypothesis, we must forget everything which has been learned in the last 70 years and start over again.” –Critic of Continental Drift in 1928
14
Harry Hess
15
Evidence: Seafloor
16
Seafloor Age
18
Seafloor Spreading
19
Earthquake Distribution
20
Volcanoes and Plate Tectonics
21
Plate Tectonics
22
Earth’s “surface” (lithosphere) is broken into plates Plates move on asthenosphere “Geology happens” where the plates interact with one another Basic Plate Tectonics
23
Crustal Properties CrustDensityCompositionThicknessAge continental ~2.8 g/cm 3 Felsic Thick: 20-70 km Old: up to 4 Byrs oceanic ~3.2 g/cm 3 Mafic Thin: 2-10 km Young: <200 Mys
24
Divergent Boundary Results in the formation of Oceanic Crust
25
Examples:
26
Transform Boundary
27
Transform Example
28
Convergent Boundary: Subduction Results in the formation & growth of Continental Crust and destruction of Oceanic Crust Melting Produces More Felsic Magma
29
Example: Pacific Northwest
30
Example: Andes Mountains
31
Convergent Boundary: Collision Results in the growth of Continental Crust
32
What Drives Plate Tectonics? Internal Heat
33
Convection Models
34
Set the “Wayback Machine” to return to the Hadean…
35
Heat Generated by Radioactive Decay Hadean Earth was much hotter! Convection was more intense
36
Rapid Convection Created “Mini” Plates that were Quickly Subducted & Destroyed
37
Subduction Creates more Felsic Volcanic Islands
38
As Plates Move - Islands “Accrete” to Form Larger Islands
39
Greenstones & Tonalites (Granites)
40
Continental Crust Forms 3.96 Billion Year Old Gneiss
41
Archean Crust Oldest Rocks Oldest Minerals
42
Continental Evolution: One Reconstruction Up to 60% by the Proterozoic
Similar presentations
© 2024 SlidePlayer.com. Inc.
All rights reserved.