Week Four – Volcanoes
Today we visited the
volcanoes called Mount Fuji in Japan.
Since this is our first trip to Japan we had to see their sacred
mountain of Mount Fuji. On our two-day
trip to the mountain we learned that Mount Fuji is a whopping 12,388 feet tall
with a base diameter of around 30 miles and a circumference around 78
miles. The top of the mountain has a
crater that is about 1600 feet in diameter and about 820 feet deep. The whole family thought it was impressive to
learn that Mount Fuji is actually a volcano that hasn’t erupted since 1707. Even though it hasn’t erupted in over 300
years it is still labeled an active volcano according to geologist (Britannica, n.d.).
The volcano is a composite cone or stratovolcano with a steep summit and
gradual slopes on the sides. This is due
to how the volcano was built over the hundreds of thousands of years. The lava that flowed from this volcano was
very thick and as a result when it was getting closer to the surface it was
encountering less pressure and the gases that are contained inside the magma quickly
release and expanded to hundreds of times their original volumes and send rock,
lava and other pyroclastic materials into the air. This pyroclastic material helped shape the nicely
sloped sides of the mountain. Once the
initial eruption happened the thick lava keep flowing, but since it is so thick
it does not flow as easily and creates steeper summits. This cycle continued over the thousands of
years to create the beautiful Mount Fuji we visited today (Lutgens &
Tarbuck, 2015) (p. 130 – 141).
From 8000 to 4500
years ago the volcano had explosive eruptions and then from 4500 to 3000 years
ago the eruptions provided a steady flow of the thick lava. 3000 to 2000 years ago most eruptions took
place at the summit and on the flank making over 100 flank cones. The last and the largest was during the 1707
eruption that left ash and debris as far away as Tokyo (Volcano Discovery, n.d.).
I believe that
geologist still say the volcano is active due to the amount of time that can
happen between eruptions. So, who knows when
it will erupt again. A volcano can only
be called dormant if it has no activity for 2,000 years (Reuters, 2001).
The mountain is located above the area where three tectonic plates
converge. The three plates are the
Amurian, Okhotsk, and Filipino plates (National Geographic,
2011). With all that plate action
and small earthquakes many believe the mountain is having magma raising into
its chamber and building up pressure getting ready to blow again. Since there is a large population so close to
the mountain many monitoring devices are used on the mountain to try and
estimate if the mountain will erupt again.
These include global positioning system arrays, seismometers, and art
laser mapping technology (Wolman, 2006).
I can see using the
laser mapping technology, since during one of my geology courses at Regis
University I remember that in a video it discussed how the base of a volcano
will expand or increase in size before it is going to erupt.
Mount Fuji with reflection in lake (National Geographic, 2011).
References
Britannica.
(n.d.). Mount Fuji. Retrieved from https://www.britannica.com/place/Mount-Fuji
Lutgens, F.
& Tarbuck, E. (2015). Essentials of
Geology (12th ed.). Upper Saddle River, NJ: Pearson Education,
Inc.
National
Geographic. (2011). Mount Fuji. Retrieved
from https://www.nationalgeographic.org/media/mount-fuji/
Reuters.
(2001). Japanese Scientists to Closely
Monitor Mount Fuji. Retrieved from https://www.nytimes.com/2001/02/07/science/japanese-scientists-to-closely-monitor-mount-fuji.html
Volcano
Discovery. (n.d.). Mt Fuji volcano. Retrieved
from https://www.volcanodiscovery.com/fuji.html
Wolman,
D. (2006). Mount Fuji Overdue for
Eruption, Experts Warn. Retrieved from https://news.nationalgeographic.com/news/2006/07/060717-mount-fuji_2.html
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