BP 6 Rates and scale of earth change are difficult to comprehend either too slow relative to human life or too huge in scale to imagine Related to how old we think the earth is Prior to late 18 ID: 1021906
Download Presentation The PPT/PDF document "B.P. #5 Present state of earth is tempo..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
1. B.P. #5 Present state of earth is temporary - different in past, futureB.P. #6 Rates and scale of earth change are difficult to comprehend – either too slow relative to human life, or too huge in scale to imagineRelated to how old we think the earth is ----Prior to late 18th century – earth = young; unchanging1790’s on = earth processes the same as today; implies old earthHow old?? 4.55 billion years old
2. Implications of huge amount of time – (“deep time”)Events that occur so slowly as to seem unimportant become important. Given time, unlikely events WILL eventually occur.
3. B.P. #4 Materials move within each sphere and between spheresPlate tectonic cycle
4. Cycling of Earth Materials – Plate tectonic cycleKEY TO HOW THE EARTH WORKS - NEW IDEA (1960’s) Historical background – What they knew in the early 1900’s Continents and ocean floors – are different Features of continents & forces that formed them Continental drift – (1915) Alfred Wegener Reaction to Wegener
5. Height of the earth’s surface -BAWhat are the most common elevations of the earth’s surface?
6. Height of the earth’s surface - the hypsographic curve BAWhat are the most common elevations of the earth’s surface?4-6 km below sea level, 0-1 km above sea level
7. How does this fit with Big Points from last week?What is the elevation of the ocean crust relative to the continental crust?Why is the ocean water where it is?What is the density of the ocean crust relative to continental crust?
8. What is the elevation of the ocean crust relative to the continental crust? LowerWhy is the ocean water where it is? Water fills in low areasWhat is the density of the ocean crust relative to continental crust? Ocean crust is more dense than continental crust - lowerHow does this fit with Big Points from last week?
9. Cycling of Earth Materials – Plate tectonic cycleKEY TO HOW THE EARTH WORKS - NEW IDEA (1960’s) Historical background – What they knew in the early 1900’s Continents and ocean floors –different crusts Features of continents & forces that formed them Continental drift – (1915) Alfred Wegener Reaction to Wegener
10. 1. Folded Mountains
11.
12.
13. Appalachian Mtns
14. When layers of rocks are laid down - they are horizontal
15. rocks in folded mountains
16. What has happened to the rocks in folded mountains?Folded - not horizontal What force caused this?yields
17. What has happened to the rocks in folded mountains?Folded - not horizontal What force caused this?yieldsCompression -
18.
19. Folded mountains, Pennsylvania
20. Folded mountains, Pennsylvania
21. 2. Rift systems
22. b. Rift systems - Sea levelSide viewHow can a valley be formedthat is below sea level?
23. 2. Rift systems - Sea levelSide viewHow can a valley be formedthat is below sea level?Not by river erosion - rivers run toocean.. Are not lower than sea level.Force?
24. 2. Rift systems - Sea levelSide viewHow can a valley be formedthat is below sea level?Not by river erosion - rivers run toocean.. Are not lower than sea level.Force? Tension
25. Rift valley - water can’t drain to ocean (why?) and soevaporates leaving white salts (Death Valley, CA)
26. Basin and Range from space, rift system - forces? xX = Death Valley area of previous slide
27. ~Canada~central USThis is a cross-section view.3. craton
28.
29. ~Canada~central USThis is a cross-section view.
30. Red = Canadian shield
31.
32. Questions about shield:-- Where were these rocks formed - folded not broken? -- How did they get to the surface? -- Why are they so old? -- Where do they go to find the oldest rocks on earth? -- Where is ours?
33. Questions about shield:-- Where were these rocks formed - folded not broken? Deep in earth-- How did they get to the surface? -- Why are they so old? -- Where do they go to find the oldest rocks on earth? -- Where is ours?
34. Questions about shield:-- Where were these rocks formed - folded not broken? Deep in earth-- How did they get to the surface?Overlying miles of rocks were eroded… then pushed up… isostasy -- Why are they so old? -- Where do they go to find the oldest rocks on earth? -- Where is ours?
35. Questions about shield:-- Where were these rocks formed - folded not broken? -- How did they get to the surface? -- Why are they so old? Takes long time for erosion and uplift.. -- Where do they go to find the oldest rocks on earth? -- Where is ours?
36. Questions about shield:-- Where were these rocks formed - folded not broken? -- How did they get to the surface? -- Why are they so old? Takes long time for erosion and uplift.. -- Where do they go to find the oldest rocks on earth?Shields -- there is a shield on every continent -- Where is ours?
37. Questions about shield:-- Where were these rocks formed - folded not broken? -- How did they get to the surface? -- Why are they so old? Takes long time for erosion and uplift.. -- Where do they go to find the oldest rocks on earth?Shields -- there is a shield on every continent -- Where is ours? In Canada - northern MI, north NY
38. ~Canada~central USThis is a cross-section view.c. Craton - 2nd part = stable platform(covered shield)
39. Nashville - covered shield - horizontal sedimentary rocks
40. CoveredShield =Blue, yellowGreen
41.
42. Covered shield (platform) - note horizontal layers
43. Cycling of Earth Materials – Plate tectonic cycleKEY TO HOW THE EARTH WORKS - NEW IDEA (1960’s) Historical background – What they knew in the early 1900’s Continents and ocean floors –different crusts Features of continents & forces that formed them Continental drift – (1915) Alfred Wegener Reaction to Wegener
44. Wegener’s lines of evidence that continents drifted1. Fit of the continents
45.
46. ~4 km thick Pm-J continental deposits2. Similar sequence of rocks on all southern continents
47.
48. 3. Similar fossils on all southern continents
49. Without hair?LystrosaurusWith hair?