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Pachamama Geography
Consultants
Dr. Wallace, Dr. Sanghe, Dr. Sandhu and Dr.
Morrison
Geographical Location and Physical Site
Nestled between the Carbon and Puyallup Rivers,
Orting is small suburban town located at 47°5′46″
N 122°12′19″W. The relatively flat terrain of Orting
makes it an ideal site for agriculture, so the
periphery of the town is composed of large acres
of farmland. The town is also bordered by a large
forest on its northeastern border, along the
Carbon river. The town is roughly 28 miles away
from MT. Rainer National Park. Sections of the
town are composed of solidified mud flows that
originated on Mt.Ranier.
Orting WA and the muddy Carbon river by James Duffin
Subduction zone
Subduction is a geological process that takes place at convergent
boundaries of tectonic plates where one plate moves under another and
is forced down into the mantle. Regions where this process occurs are
known as subduction zones. Rates of subduction are typically in
centimetres per year, with the average rate of convergence being
approximately two to eight centimetres per year along most plate
[1]
boundaries.
Plates include both oceanic crust and continental crust. Stable
subduction zones involve the oceanic lithosphere of one plate sliding
beneath the continental or oceanic lithosphere of another plate due to
the higher density of the oceanic lithosphere. That is, the subducted
lithosphere is always oceanic while the over-riding lithosphere may or
may not be oceanic. Subduction zones are sites that have a high rate of
volcanism, earthquakes, and mountain building.
An explanation of subduction, and why the cascade volcanoes exist.
The Cascade Volcanoes (also known as the Cascade Volcanic Arc or the Cascade Arc) are a number of volcanoes in a volcanic
arc in western North America, extending from southwestern British Columbia through Washington and Oregon to Northern California, a
distance of well over 700 miles (1,100 km). The arc has formed due to subduction along the Cascadia subduction zone. Although
taking its name from the Cascade Range, this term is a geologic grouping rather than a geographic one, and the Cascade Volcanoes
extend north into the Coast Mountains, past the Fraser River which is the northward limit of the Cascade Range proper.
The Cascadia subduction zone (also referred to as the Cascadia fault) is a convergent plate boundary that stretches from northern
Vancouver Island to northern California. It is a very long, sloping subduction zone that separates the Explorer, Juan de Fuca, and
Gorda plates, on the one hand, and the North American Plate, on the other.
The denser oceanic plate is subducting beneath the less dense continental plate offshore of British Columbia, Washington, Oregon,
and northern California. The North American Plate moves in a general southwest direction, overriding the oceanic plate. The Cascadia
subduction zone is where the two plates meet.
History of eruptions
There are Five main growing stages in the history of Mount Rainier. The first date back half a million years when there
began calumnious and continuous volcanic rock. There was geothermal activity before but not until this point did Rainier
begin taking its shape.
500 to 420 ka - Old Desolate – Rapid accumulation of lava
First 80000- the volcano was very active. A thick apron of pyroclastic flows emerged over the glacier.
420 to 280 ka - Rampart – Reduced rate of lava accumulation
280 to 160 ka - Mowich – Rapid accumulation of lava
160 to 40 ka - Little Tahoma – Reduced eruptions and erosion of the upper mountain
40 to 15 ka - Point Success – Reconstruction of the upper mountain
11 ka to present - Holocene eruption period
2,700 to 2,000 years ago – Summerland eruptive period
1,500 years ago – Twin Creek eruptive episode
1,100 to 1,000 years ago – Fryingpan Creek eruptive period
500 years ago – Electron Mudflow
The most recent recorded volcanic eruption was between 1820 and 1854, but many eyewitnesses reported eruptive activity in 1858,
1870, 1879, 1882 and 1894 as well
Potential hazards of Mount Rainier
Eruption: can cause lava flow, the falling of volcanic
ash and pyroclastic flows (avalanches of hot ash,
lava and volcanic gases flowing at great speed).
Which can lead to
the melting of snow and ice and can produce torrents
of meltwater which pick up loose rock and become
rapidly flowing slurries of mud and boulders known as
lahars.
Specific Risks to Orting
Lahars, rapid mud flows resulting from a volcanic eruption, pose the biggest risk to
Orting. Lahars pose a risk to buildings in Orting as geological evidence indicates
that past lahars have made their way to Orting before.
Studies by U.S. Geological Survey (USGS) suggest that there may be little to no
warning . According to geology.com, “if a large lahar were generated in the upper
Puyallup River valley without the precursors that typically herald volcanic unrest
and eruption, it could arrive at the City of Orting as little as 40 minutes after the
initial warning is sounded”
Conclusion: recommendations
Taking into account the hazards of Mount Rainier, the geographical location of
Orting and the subduction zone in which it is located, we conclude that it is
geographically unsafe to build a community college on this site. However, there
has been little to no activity in the past 100 years. Given the fact that people still
live in Orting, the establishment of proper evacuation plans and exits are
necessary before any development.