1. Week 13 - Mod 6 Foundations of Geology
Part 2
Sections:
Erosion
Bringing it All Together: The Basic
Structure of the Grand Canyon
Next Time

2. Erosion
Back to the Grand Canyon, we saw that weathering had a big part of shaping this famous monument, but something else helped… EROSION: the process by which sediments and rock fragments are carried away by wind or rainwater. Read Exp. 6.5 (another EXTRA CREDIT experiment. 2 2

3. Erosion
Observations… What would happen if it was just dirt? What happens when the sod is in place? The faster the water, the faster the erosion. And then you have the wind whipping things up. But erosion by water is most common. What happens to all the material from erosion? Depends on what water did the eroding? 3 3

4. Erosion
Creeks lead to streams which lead to rivers… where do rivers end… the ocean. With each new level, the water gains strength and more & more sediment is carried away. What happens in a flood? ______________ Remember any floods lately? Look at the Nile River, the _________ river in the world – Figure 6.4 4 4

5. Erosion
What is at the end of the river? __________ Oceans have tides, deposit sand and make a beach. Lake Michigan – Chicago – erosion of the shoreline. Streams and rivers move it, lakes fill in with it, and oceans redistribute it – sediments. The author calls erosion Creation’s way of recycling sediments. 5 5

6. Underground Erosion
Underground water exists and it can erode the earth and create what's called a cave, a cavern, or a sinkhole. Caverns can be very large and go on forever – Kentucky has one 348 miles long. Sinkholes are when water erodes the Earth underneath and the surface collapses into the hole. Can be due to broken storm water pipes or natural disasters. 6 6

7. Underground Erosion - Sinkholes7 7

8. Underground Erosion - Sinkholes8 8

9. Underground Erosion
When water drips into the cavern, it carves it out & creates stalactites & stalagmites – Figure 6.5 Particles in the water start on the ceiling and form an icicle or if big enough, drip to the floor and form a mass. 9 9

10. Underground Erosion
stalactites – icicle-like structure hanging down. stalagmites – statue-like structure rising from the ground. When these 2 formation touch, they form a “column”. Lincoln Memorial – stalagmites in the basement – it’s made out of stone. “On Your Own” 6.7 & 6.8 10 10

11. Bringing it All Together: The Basic Structure of the Grand Canyon
Learned about many things so far – erosion, types of rock, and different weathering. Look at Figure 6.6 in detail. Notice that the rock of the G. C. is stratified. Look at dashed line – example of Unconformity Defined: a surface that separates one layer of rock from another. There are many unconformities in the Grand Canyon, but the one pointed out is most striking. 11 11

12. Bringing it All Together: The Basic Structure of the Grand Canyon
Angular Unconformity – layers at distinct angles to each other. The rocks below are tilted relative to the rocks above. Because it is so striking, this unconformity is called the Great Unconformity of the Grand Canyon. 12 12

13. Bringing it All Together: The Basic Structure of the Grand Canyon
There are 3 other types – NONconformity - area where stratified layers meet UNstratified layers. Disconformities – parallel, stratified rock layers above & below the unconformity, but with a clear surface of erosion. Paraconformities – a layer that geologists believe contains an unconformity, but can’t find it. 13 13

14. Bringing it All Together: The Basic Structure of the Grand Canyon
READ ALONG: p. 155, paragraph 4. What formed the Great Unconformity in the Grand Canyon? The sides argue over the details, but they both agree that rocks below the angular conformity were tilted by some major event like an earthquake. Then the rocks above the angular unconformity were laid down. 14 14

15. Bringing it All Together: The Basic Structure of the Grand Canyon
Intrusion – a vein of igneous rock through several layers of sed. rock. Sills and dikes – parallel & perpendicular veins of igneous rocks. 4 types of rocks in the G. C. – igneous, metamorphic, and sedimentary rock, and finally, igneous rock at the surface from volcanic eruptions. 15 15

16. Bringing it All Together: The Basic Structure of the Grand Canyon
The G. C. is a spectacular sight in the US visited by people from all over the world. It’s highlighted here because it is a good general representation of the geological characteristics of our planet. Contains all 3 basic rock groups, has many strata, and several unconformities. Thus it contains all the major geological features that you will find on earth. 16 16

17. Bringing it All Together: The Basic Structure of the Grand Canyon
Next module we discuss fossils that one can find in rocks like those of the G. C. Fossils tell us a lot about the history of life and can tell us a lot about geology itself. Next module, we’ll sum it all up with a comparison between the 2 views of the formation of the earth – Uniformitarianism vs. Catastrophism… or the Unis VS the Cats. 17 17

18. For Next Time
Write up “On Your Own” 6.7, 6.8, 6.9, and Write up Experiment 6.2 – “Separation of Sedimentation” if not done yet. Take Module 6 test EXTRA CREDIT: Experiments 6.1, 6.3, and 6.4 18 18