Assignment #2
- 1. Assignment #2 Earthquakes & Volcanoes Dustin Collins & Mak Soden December 3rd 2014 Chris Melmoth Algonquin College
- 2. 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.
- 3. 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.
- 4. Bodies from the disaster What remained of Tokyo More Destruction Japan is no stranger to earthquakes, in fact there have been 68 recorded
- 5. 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 TōhokuEarthquake 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.
- 6. 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.
- 7. 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.
- 8. 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.
- 9. 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.
- 11. 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.
- 12. 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.
- 13. 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.”
- 14. “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.”
- 15. 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.”
- 16. 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
- 17. 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: (n.d.). Retrieved November 27, 2014, from 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
- 18. (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: Applying geoscience to Australia's most important challenges. (n.d.). Retrieved November 27, 2014, from http://www.ga.gov.au/scientific-topics/hazards/volcano/basics/causes (2002, January 18). Retrieved November 27, 2014, from http://news.bbc.co.uk/cbbcnews/hi/find_out/guides/tech/volcanoes/newsid_1768000/1768595.stm 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