Assignment #2

Earthquakes & Volcanoes

Dustin Collins & Mak Soden

December 3rd 2014

Chris Melmoth

Algonquin College

Earthquakes

What are earthquakes, and what causes them?

An earthquake is a sudden and destructive shaking of the

earth’s upper layer. Earthquakes occur in areas where two or

more “plates” touch each other. When these plates rub or

fracture, they release enormous amounts of energy in the

form of seismic waves. There are different types of

earthquakes. These are called foreshocks, mainshocks, and

aftershocks. If a mainshock is large enough, the aftershocks can continue for days, weeks, and

even months or years!

Definition: a sudden and violent shaking of the ground, sometimes causing great destruction, as a

result of movements within the earth's crust or volcanic action.

So how do these plates create earthquakes? The earth has four

major layers: the inner core, outer core, mantle and crust. The top

portion of the mantle as well as the crust, are where we find tectonic

plates. Tectonic plates and the edges of the plates are called the

plate boundaries. These plates move around the surface of our

planet, and fit together like puzzle pieces. Since the edges of

the plates are rough, they get stuck while the rest of the plate

keeps moving. When a plate has moved far enough, the

edges unstick or break on one of the faults and there is an

earthquake. When the plates move around we find that most

earthquakes will happen where these plates touch. These

zones are where the majority of earthquakes occur. When an

earthquake occurs underwater we can get another dangerous natural phenomenon, these are

called Tsunamis. The energy that radiates outward from the fault can displace a plate, resulting

in the displacement of water. If the earthquake occurs close to land the resulting effect is a

massive wave of displaced water that is incredibly dangerous.

Historic & Recent Earthquakes

In this next section we will look at two major earthquakes that have occurred. One will be from

the past, while the other will have occurred in more recent times. We will look at the magnitude

of the quake, as well as where it was located and how much destruction it caused.

The Great Kantō Earthquake, Tsunami, and Fire (1923)

In 1923 at 11:58 a.m., a large earthquake from a

seismic fault six miles beneath the floor of

Sagami Bay near Tokyo hit Japan. A 60- by 60-

mile segment of the Philippine oceanic plate

slipped past a portion of the Eurasian continental

plate convergent boundary where the Philippine

Sea Plate is sub-ducting beneath the Okhotsk

Plate along the line of the Sagami Trough. This

released a massive burst of tectonic and seismic energy. The earthquake was a magnitude 7.9,

and caused massive amounts of damage. Many buildings were destroyed in Yokohama and

Tokyo, but this was not the end of the destructive earthquakes power. Shortly after the

earthquake a large 40 foot waver decimated the area around the two cities. When the water

retreated back to ocean it dragged with it thousands of people. The death did not stop there

though, as fires burned their way across the region destroying whatever remained from the initial

quake and tsunami. In the end there were just over 140,000 dead, 44,000 of those were burned

alive from the fires when they sought shelter from the quake around Tokyo’s Sumida River. All of

Yokohama, and Japan’s Capital were destroyed. The Japanese government even discussed moving the

nation’s capital to a different city in the weeks after the quake. The aftershocks and fires injured 502,000

and left 3.25 million homeless. About 80 percent of the dwellings in Yokohama and 60 percent of those

in Tokyo were destroyed.

For more photos of the devastating earthquake, tsunami and fire of 1923, see the following page.

Bodies from the disaster

What remained of Tokyo

More Destruction

Japan is no stranger to earthquakes, in

fact there have been 68 recorded

earthquakes in and around the islands of Japan dating back to 684 AD. All of Japan’s

earthquakes are the result of the subduction of the Philippine Sea Plate beneath the continental

Amurian Plate and Okinawa Plate to the south, and subduction of the Pacific Plate under the

Okhotsk Plate to the north. This is an area where the continuous movements of the tectonic

plates, creates a dangerous seismic area for the Japanese people. This became true again in 2011.

The Tōhoku Earthquake and Tsunami (2011)

In 2011 an earthquake with a magnitude 9.0 hit Japan,

this was the strongest earthquake to have hit the islands

of this nation. It was also the fourth largest earthquake

in the world since modern record keeping began. The

earthquake triggered a tsunami that hit the coast and

traveled almost 10km inland. The earthquake itself

pushed Japan’s main island (Honshu) two and a half

metres east. It also shifted the Earth’s axis, estimates

place this movement from 4-10 inches. This quake was

truly destructive.

Shortly after the quake and tsunami, the Japanese police, rescue workers, and government

release some startling statistics. There were15,889 deaths, 6,152 injured, and 2,601 people

missing. In addition to the death toll

there were 127,290 buildings totally

collapsed, 272,788 buildings 'half

collapsed', and another 747,989

buildings partially damaged. Over four

million homes in northeast Japan were

without power, and one and a half

million without running water.

The tsunami also caused the critical

meltdown of the Fukushima Daiichi,

Fukushima Daini, Onagawa Nuclear

Power Plant and Tōkai nuclear power

stations , which is still putting thousands of

gallons of nuclear material into the Pacific

Ocean. The estimated cost of the destruction

was 235 billion U.S dollars, making it the

most expensive natural disaster in human

history. Over 340,000 people were displaced

from the tsunami, many have never been able

to return to their homes due to the radiation

seeping out from the Fukushima Daiichi

power plant.

References

Info

Hammer. J. (May 2011). The great japan earthquake of 1923. Retrieved from:

http://www.smithsonianmag.com/history/the-great-japan-earthquake-of-1923-

1764539/?no-ist

Factsanddetails. (n.d). Great Tokyo earthquake of 1923. Retrieved from:

http://factsanddetails.com/japan/cat26/sub160/item2226.html

Wald. L. (n.d) The green frog news. Retrieved from:

http://earthquake.usgs.gov/learn/kids/eqscience.php

Pictures

Logsoku. (1923). 1923 Earthquake japan. Retrieved from:

http://www.logsoku.com/r/poverty/1334150736/

Factsanddetails. (n.d). Great Tokyo earthquake of 1923. Retrieved from:

http://factsanddetails.com/japan/cat26/sub160/item2226.html

Kyodo News. (2011). Before and after. Retrieved from:

http://blogs.sacbee.com/photos/2011/03/japan-one-week-after-the-earth.html

All other pictures are public domain.

Volcanoes

What are volcanoes, and what causes them?

“When a part of the earth's upper mantle or

lower crust melts, magma forms. A volcano is

essentially an opening or a vent through which

this magma and the dissolved gases it contains

are discharged. Although there are several

factors triggering a volcanic eruption, three

predominate: the buoyancy of the magma, the pressure from the exsolved gases in the magma

and the injection of a new batch of magma into an already filled magma chamber. What follows

is a brief description of these processes.

As rock inside the earth melts, its mass remains the same while its volume increases, producing a

melt that is less dense than the surrounding rock. This lighter magma then rises toward the

surface by virtue of its buoyancy. If the density of the magma between the zone of its generation

and the surface is less than that of the surrounding and overlying rocks, the magma reaches the

surface and erupts.

Magmas of so-called andesitic and rhyolitic compositions also contain dissolved volatiles such as

water, sulfur dioxide and carbon dioxide. Experiments have shown that the amount of a

dissolved gas in magma (its solubility) at atmospheric pressure is zero, but rises with increasing

pressure.

For example, in an andesitic magma saturated with water and six kilometers below the surface,

about 5 percent of its weight is dissolved water. As this magma moves toward the surface, the

solubility of the water in the magma decreases, and so the excess water separates from the

magma in the form of bubbles. As the magma moves closer to the surface, more and more water

exsolves from the magma, thereby increasing the gas/magma ratio in the conduit. When the

volume of bubbles reaches about 75 percent, the magma disintegrates to pyroclasts (partially

molten and solid fragments) and erupts explosively.

The third process that causes volcanic eruptions is an injection of new magma into a chamber

that is already filled with magma of similar or different composition. This injection forces some

of the magma in the chamber to move up in the conduit and erupt at the surface.

Although volcanologists are well aware of these three processes, they cannot yet predict a

volcanic eruption. But they have made significant advances in forecasting volcanic eruptions.

Forecasting involves probable character and time of an eruption in a monitored volcano. The

character of an eruption is based on the prehistoric and historic record of the volcano in question

and its volcanic products. For example, a violently erupting volcano that has produced ash fall,

ash flow and volcanic mudflows (or lahars) is likely to do the same in the future.

Determining the timing of an eruption in a monitored

volcano depends on measuring a number of parameters,

including, but not limited to, seismic activity at the

volcano (especially depth and frequency of volcanic

earthquakes), ground deformations (determined using a

tiltmeter and/or GPS, and satellite interferometry), and

gas emissions (sampling the amount of sulfur dioxide

gas emitted by correlation spectrometer, or COSPEC).

An excellent example of successful forecasting occurred

in 1991. Volcanologists from the U.S. Geological survey accurately predicted the June 15

eruption of the Pinatubo Volcano in the Philippines, allowing for the timely evacuation of the

Clark Air Base and saving thousands of lives.”

What are the 4 different types of volcanoes?

Geologists generally group volcanoes into four main kinds cinder cones, stratovolcanoes, shield

volcanoes, and calderas.

Cinder cones

Stratovolcanoes

Shield Volcanoes

Calderas

Typical places where volcanoes occur:

Volcanic activity frequently occurs at the boundaries of the Earth's tectonic plates, which are

large masses of rock moving between each other. The movement of these plates plays a

significant role in the type of volcano formed, which influences its shape.

Spreading plate margins

Where plates move away from each

other at spreading or divergent plate

margins, volcanic eruptions are gentle

extrusions of basaltic lava. Most of

these occur underwater where magma

rises from great depth below to fill the

space created by seafloor spreading

which occurs at a rate of about 10 centimetres a year.

Subducting plate margins

At subducting plate margins, one plate is pushed

under a neighbouring plate as they squeeze

together. In addition to the older, denser plate

being forced down and melted, wet sediment

and seawater is forced down creating granitic

lava and more violent eruptions containing

ash. These volcanoes form classic cone shapes.

Some volcanoes are found at great distances from plate boundaries and are referred to as intra-

plate, within plate or hot spot volcanoes. These form above hot mantle upwellings or plumes

which rise from great depths. As the plate overlying the plume moves away from the hot spot

and a new volcano is formed, the previous one cools to become dormant and eventually extinct.

This sequence forms a volcanic chain such as that currently found in the Hawaiian Islands.

Hotspot volcanism forms very large, low gradient shield volcanoes and are similar in

composition and eruption style to those found at divergent plate boundaries.

Historic & Recent Eruptions

“Mount Fuji: Is the highest volcano and highest peak in Japan and considered one of the 3 Holy

Mountains (along with Mount Tate and Mount Haku). Fuji is a perfect stratovolcano about 60

miles south-west of Tokyo, with an exceptionally symmetrical shape making it into famous

symbol of Japan and an important element in Japanese art. It is a popular destination for

excursions travelers, tourists and hikers. More than 200,000 people climb to the top of the Mt

Fuji every year. The last eruption of Mt Fuji was in 1707–08. Between 2000 and 2001, seismic

activity under the volcano was at slightly elevated levels, rising concern about a possible

reawakening of the volcano.”

“Mt Fuji has a complex geologic origin. The large stratovolcano has a base diameter of almost

50 km and culminates in a 500 m wide and 250 m deep summit crater. The volcano overlies

several older volcanoes, whose remnants form irregularities on Fuji's symmetrical profile,

including Komitake and Ko-Fuji (Older Fuji) which was active 100,000 - 10,000 years ago.”

“The present-day, mainly basaltic edifice started to grow about 11-8,000 years ago when large

lava flows were erupting, that still form 25% of the volume of the structure today. From 8000 to

4500 years ago, Fuji's activity was mainly explosive before another effusive cycle took place

between 4500 to 3000 years ago. In the past 3000 years, large explosive eruptions occurred in

between phases of milder vociferous activity. From 3000 to 2000 years ago, most eruptions took

place at the summit, while a large number of flank eruptions occurred during the past 2000 years,

forming more than 100 flank cones.

The last confirmed eruption of Mt Fuji took place in 1707 and was Fuji's largest during historical

time. It deposited ash as far as present-day Tokyo and formed a large new crater on the east

flank.”

1707 eruption of Mt Fuji

“On 26th October 1707, a new eruption announced itself with a large 8.4 magnitude earthquake

devastating Honshu island, followed by several smaller earthquakes felt near Mt Fuji.

The eruption started on 16th December 1707 from a new vent on the SE flank of the volcano

erupting a sub-plinian column of ash and pumice, turning into basaltic lava fountaining after 6

hours into the eruption. On the first day of the eruption, 72 houses and 3 Buddhist temples were

destroyed in Subassiri town 10 km from the volcano. Ash fell all over the south Kanto plain,

Tokyo, and on areas of the NW Pacific Ocean 280 km from the volcano. The total volume

erupted over 16 days was estimated to 0.68 cubic km of magma. Violent explosions were

recorded until 25-27 December, before the eruption calmed down and ended on 1st January

1708.”

Japan’s newest volcanic island

A new island emerged on 20 November 2013 out of the ocean as the result of a Surtseyan

eruption on the S flank of Nishinoshima, a small volcanic island in the Izu-Bonin arc, ~940 km S

of Tokyo (figure 1). The new island, originally called Niijima ('new island') by the Japan Coast

Guard (JCG), eventually merged with Nishinoshima on 24 December 2013. It’s described the

now merged islands under the name 'Nishinoshima.'”

“Further background: The new island was

located in the Volcano Islands, a group of

three Japanese active volcanic islands that lie

atop the Izo-Bonin-Mariana arc system that

stretches S of Japan and N of the Marianas.

According to the Geological Survey of Japan,

Nishinoshima was an emerged submarine

volcano in 1974 with a height of ~3,000 m

from the surrounding ocean floor and ~30 km

wide at its base.”

November 20th

November 21st

December 24th

January 20th

“In summary, the new addition to Nishinoshima grew

500 m SSE of the island's S flank, beginning 20

November 2013, from a depth of 50 m to a height of 65

m from an originating time no earlier than 1974, the time of the latest addition to the island.

Based on continued emissions and satellite-based thermal alerts, it is apparent as of 13 March

2014 that Niijima was still expanding outward in all directions from the vents, and that

Nishinoshima had grown to over three times its original size.”

References

Images taken from:

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http://thebritishgeographer.weebly.com/uploads/1/1/8/1/11812015/8944472.jpg?353

What causes a volcano to erupt and how do scientists predict eruptions? (n.d.). Retrieved November

27, 2014, from http://www.scientificamerican.com/article/what-causes-a-volcano-to/

Volcanoes: Principal Types of Volcanoes. (n.d.). Retrieved November 27, 2014, from

http://pubs.usgs.gov/gip/volc/types.html

(n.d.). Retrieved November 27, 2014, from http://images.mapsofworld.com/travel-blog/mount-fuji.jpg

(n.d.). Retrieved November 27, 2014, from

http://www.forensicgenealogy.info/images/mt_fuji_map.gif

Global Volcanism Program | Nishinoshima. (n.d.). Retrieved November 27, 2014, from

http://volcano.si.edu/volcano.cfm?vn=284096

(n.d.). Retrieved November 27, 2014, from http://img.theepochtimes.com/n3/eet-

content/uploads/2013/11/Nishinoshima.jpg

Info taken from:

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from http://www.ga.gov.au/scientific-topics/hazards/volcano/basics/causes

(2002, January 18). Retrieved November 27, 2014, from

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What causes a volcano to erupt and how do scientists predict eruptions? (n.d.). Retrieved November

27, 2014, from http://www.scientificamerican.com/article/what-causes-a-volcano-to/

Volcanoes: Principal Types of Volcanoes. (n.d.). Retrieved November 27, 2014, from

http://pubs.usgs.gov/gip/volc/types.html

Mt Fuji. (n.d.). Retrieved November 27, 2014, from http://www.volcanodiscovery.com/fuji.html

Global Volcanism Program | Nishinoshima. (n.d.). Retrieved November 27, 2014, from

http://volcano.si.edu/volcano.cfm?vn=284096