bree_hernandez_lab_15
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Metropolitan Community College, Kansas City *
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101
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Geography
Date
Dec 6, 2023
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docx
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Mass Wasting (Lab 15)
For this lab you will need the following:
●
Google Earth
●
Mass Wasting KMZ file (posted in lab 15 assignment link in Canvas)
Location 1: Mt. St. Helens
●
Click the link for the “Mass Wasting” KMZ file to begin this activity.
●
Open the “Location 1: Mt. St. Helens Lahar” folder and click the icon for the “Mt. St. Helens
Lahars” placemark to fly to it. Open the placemark balloon. Click through to the lahar images
linked there.
●
Click and fly to the icon for placemark A, and open placemark A’s balloon. The image is of the
Toutle River valley lahar, taken 24 years after the eruption.
●
Click and fly to the icon for placemark B, and view the close-up image of the lahar in that
placemark.
●
Click and fly to the icon for placemark C and click through to the web page detailing efforts to
control sediment flow in the downstream reaches of the Toutle River.
1.
Describe the man-made structure at placemark C, and explain how it works and why it was built.
It is a dam and it's meant to hold back water in order to control flooding, generate energy, or store water.
●
Use the Search panel to fly to Orting, Washington.
2.
Notice that Orting is located at the confluence of two rivers. The river NE of town is the Carbon River,
the river to the SW is the Puyallup River. Trace both of those rivers upstream, and describe the location
and source of water for those streams.
They both originate from Mt. Rainier.
3.
What hazards would the inhabitants of Orting face in the event of an eruption of Mt. Rainier (25 miles
SE of Orting), and what plans can be made or actions can be taken to prevent loss of life and property if
an eruption occurs?
A polluted river, smoke, and volcanic ash and sediment would all pose a threat. A sediment retention
structure, such as the one seen in the Tootle River, might be an option to keep the material from
reaching them.
4.
Search for Carbonado, Washington, and explain why the inhabitants of Carbonado, though closer to
Mt. Rainier, are in less immediate danger of inundation by a lahar if Mt. Rainier were to erupt.
The inhabitants of Carbonado, Washington are less in immediate danger from lahar due to eruption of
Mt. Rainier because they are protected by their location and the surrounding vegetation, which creates
friction and reduces the speed of a lahar. The inhabitants can also easily evacuate as they are near roads
and highways.
5.
Compare the appearance of the Puyallup and Carbon River valleys around Orting with the Toutle River
valley at placemark A. How are the valleys similar? And how are the valleys different?
All three rivers appear to be braided, but the Toutle appears to have cut out a broader valley as a result
of the water's cutting action.
6.
Describe any evidence you see that suggests the Puyallup and Carbon River valleys have been the sites
of lahars in the past.
Lahar flow has previously occurred in the Puyallup and Carbon River valleys. They're in a good location
due to the fact that the river receives water from a neighboring glacier.
Location 2: La Conchita, California
●
Open the “Location 2: Coastal California” folder and click the icon for the “Location 2: La
Conchita Landslide” placemark to fly to it, and open the placemark balloon. Click through to
view the video (works best in Internet Explorer) and read the description of the January, 2005
event.
1.
What geologic conditions existed in the area prior to the 2005 slide that pre-disposed the area to
future slides?
The houses were all built at the base of a steep slope that had already experienced a slide prior. Experts
had also declared it was a recurring slide.
2.
What were the immediate causes of the 2005 slide?
The landslide occurred after a 15-day period of unprecedented records of rainfall in Southern California.
Seasonal rainfall had been constant in the area, triggering a slope failure.
3.
Determine the gradient between placemarks A and B (on the slide itself) and between placemarks C
and D on the intact slope adjacent to the slide.
Gradient on the slide = __
35%_____ Gradient on the intact slope = ___
50%_____
4.
Describe how the occurrence of the slide helps to stabilize the material that has failed during the slide.
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