The Scablands of Washington state are a remarkably eroded. But how? That's what this NOVA episode is about. How were the Scablands formed, and how did the science community do its work? Sometimes it worked better than at other times. Dearly held beliefs compete with empirical evidence. Just as with Wegener's idea about continental drift and Alvarez's idea about an asteroid impact that killed the dinosaurs, beliefs closed geologists' minds to the empirical evidence that supported a very different idea. Is this good, or is it bad? Assignment:
A dramatic example of erosion in Arizona is Antelope Canyon. The picture below shows the canyon from inside. The video below the picture shows what it looks like from the ground surface at the top of the canyon during a flash flood; it sort of just looks like a crack in the ground, doesn't it! But this video was taken during a flash flood that went through the canyon. Remember, the canyon is 30 to 40 feet deep. All we are looking at is the top! Pretty violent! Rivers flow faster in some situations and slower in others. Rivers flow at different speeds in different places within their currents. As a result, erosion is greater in some locations than in others. One effect of this is that rivers meander. It's what rivers do, given enough time. We can see this happen over about 28 years in the YouTube videos linked below. Can you find the cut banks? the point bars? the oxbow lake? the cutoff? Assignments:
Erosion and deposition are important processes in shaping Earth's surface, and not only Earth's but also Mars. We'll stick to Earth, though.
Erosion is our new concern, and we learned four different agents of erosion today. What are they? We noted that Marcus Landslide in our very own McDowell Mountains is a notable local example of erosion which occurred about 550,000 years ago. And as we know, boulders still tumble down hills and mountains from time to time. And then there are floodplains, a source of concern and some controversy here in Scottsdale and Phoenix. We'll have more to say about that. Assignments:
We wrapped up our work with weathering and soil formation with a quiz today.
Wind, water, ice, and gravity all are causes of erosion, the movement of weathered material. Scottsdale has its flood fans and washes. Are flood fans 5 and 6 really a flooding threat? It seems they haven't had a flood in over 10,000 years! We also saw some spectacular examples of gravity's work today! Landslides, mudslides, slump, and creep filled our time today. I hope it wasn't too creepy!
Assignment:
We finished up or discussion of weathering and erosion today. We also began discussing the way that soils develop.
Assignment:
We studied different kinds of weathering today and, in particular, Karst topography.
Weathering and erosion are the processes of interest today. You should be able to describe both processes, clearly distinguishing between them. Each process is caused by several agents. You should be able to list several of these agents for both weathering and for erosion.
Assignment:
PREPARATION FOR THE SEMESTER FINAL EXAM
We continued our descriptions of motion at constant velocity and accelerated motion. See you all after Thanksgiving break!
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Earth ScienceMr. Swackhamer Archives
March 2020
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