Posted: November 16th, 2022

Particular volcanoes in the Cascade Range pose geological threats

#1
Particular volcanoes in the Cascade Range pose geological threats to nearby population centers including Seattle-Tacoma, Mount Vernon and Bellingham in Washington; Eugene, Portland and Bend in Oregon; and Weed in California.
Population Centers Volcanoes
Seattle-Tacoma Mount Rainier, Mount Adams, Glacier Peak, Mount Baker and Mount St. Helens
Portland Mount Hood, Mount St. Helens and Mount Adams
Bend Mount Jefferson, Three-Fingered Jack, Mount Washington, Pilot Butte, Lava Butte, Newberry Caldera, Belknap, Broken Top, Three Sisters and Mount Bachelor
Mount Vernon Mount Baker, Mount Vernon, Mount St. Helens and Glacier Peak
Bellingham Mount Baker, Mount Rainier
Portland Mount Hood Volcano
Weed, CA Black Butte, Mount Shasta, Lassen Peak
Eugene, OR Three Sisters, Mount Hood,
#2
Volcanic eruptions that occur after much longer intervals may pose potentially more destructive hazards compared to those that break out frequently, say after a century, for example, the Mount St. Helen eruptions. This is because for longer interval volcanic eruptions may be forgotten or overlooked and it is difficult to predict occurrences and the amounts of volcanic particles that would erupt and destroy lives and property. However, people can adopt measures to counteract and avoid the frequently occurring volcanic eruptions such as the Mount St. Helen eruptions by using the land-use zoning and avoiding or allowing least developments in the eruption prone areas.
#3
The main concentration area of tephra accumulation in the Cascade Range eruptions is Mount St. Helen. Over the past 4000 years, the area has an annual probability of 0.2% of 10 centimeters or more of Tephra concentration.
#4
The main factors that determine the spatial patterns of tephra accumulation probability of 10 cm or more per year in the Pacific Northwest from Cascade Volcanoes are the landscape patterns, site amelioration, Volume of the ejected materials, secondary disturbances and other physical conditions.
#5
Seismometer Reading of 3.5 miles after 77 seconds means that the explosion cloud moved at a speed of 163 7/11 miles per second.
This can be shown by the following calculations:
Conversion from seconds to hours: 77/3600hrs
Speed Calculation in 3.5 miles: 3.5÷77/3600=163 7/11 miles per second.
#6
The populations that the Osceola Mudflow runs beneath are the Seattle, Tacoma and Bellingham in Washington. This is because, by extension, Mt. Rainier which is prone to Lahars mostly affects the two populations.
#7
Community Response Time (minutes)
Enumclaw 80
Kent 90
Auburn 90
Tukwila 80
#8
The ecological and physical changes that have affected the flow paths of lahar and river valley since the settlement of the European include reduced vegetation cover, gulley formations due to floods, melting snows which generate water, landslides that transform the downstream patterns, and rapid water release from the crater breakages.
#9
Flow velocities are increased where vegetation there is less vegetation or forest covers. Moreover, gulley developments due to floods can change the courses of flow of both lahar and river waters. Finally, rapid water release from craters can cause breakage of craters which may ultimately hasten mudflows.
#10
I would recommend that the schools should practice evacuation procedures in case mudflows occurrences. Moreover, the schools should ensure that slopes are always stable before erecting schools. Finally, the schools should be informed of the role of FEMA in evacuations and always call their hotlines when disasters are likely to occur.
For nuclear power plants, I would recommend that the nuclear power station should develop and implement the Lahar warning techniques.
#11
Orting will need a quicker response time when compared to Tacoma. This is because the lahar, originating from Mount Rainier through Carbon Rivers and Puyallup, is a frequent disaster in Orting, arriving there before Tacoma.
#12
Volcanic hazards can be mitigated through proper urban planning in Orting city. Spatial maps showing low frequency of lahar and other volcanic activities occurrences are very useful for decision making while establishing elementary schools and other buildings within the city. Moreover, the schools should be built at the locations near evacuation routes.
#13
From the eruption history of Glacier Peak, we can observe that the recurrent intervals are proportional to the debris flow amounts. After long eruption intervals, tephra eruptions and lahars are large enough to reach the sea. Contrariwise, short intervals of eruptions result into small emission of debris and sometimes only steam is emitted.
#14
The flow might have changed its direction due to prevailing wind direction, westward slope failure, and landslide.
#15
Factors that cause avalanche deposits in Mount Rainier:
Volcanic eruptions causing Pyroclastic flow, lava flow, tephra fallouts, surges, and glacial outburst
Dormant period occurrence
Hydrothermal volcano alterations and mixed melt waters and debris
#16
From the hazard map, the debris avalanche can pose threat to Puget since the town is within the effects proximity.
#17
Mount Rainier GLOF
#18
90 minutes reaction time

Reference
Sheets, P. D., & Grayson, D. K. (Eds.). (2013). Volcanic activity and human ecology. Elsevier.

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