Summary on Earthquakes, Volcanoes and Landslides - Assignment Example

of institute Summary on Earthquakes, Volcanoes and Landslides A Research Presentation on Earthquakes, Volcanoes and Landslides and major natural calamities Name of Author [Pick the date] Contents Earthquakes: 3 Lisbon, 1755: 3 San Francisco, 1906: 5 Alaska, 1964: 5 New Madrid, Missouri, 1811 – 1812 8 What Causes Earthquakes? 8 How do we measure earth quakes? 11 Can we predict earthquakes? 11 The Psychology of earthquakes: 12 Volcanoes 12 Landslides: 15 Conclusion: 17 Earthquakes: Earthquakes are caused due to the shifting of tectonic plates. Tectonic plates are super massive colossal horizontal land masses underneath the sea bed that form the upper crust of the earth’s layers of soil. It covers the sea beds and is the foundation of land masses. Tectonic plate shifting along fault lines is the primary cause of major earthquakes. However this is not just the sole reason for earthquakes. Localised low intensity and low impact earthquakes also occur frequently everyday at different parts of the world. They are due to the shifting of underlying layer of soil, and are confined only to small localities in cities, town or rural area. Lisbon, 1755: The Lisbon Earthquake: The Lisbon earthquake in the country of Portugal back in the 1st of November 1755 was one of the most ghastly natural calamities in the memory of mankind. Nothing every of such gigantic destructive scale had ever occurred in the near recallable future, swallowing everything from a huge civilisation, to thousands of people, human constructions etc. The Lisbon earthquake due to its sheer magnitude of destruction is till date studied by geologists, seismologists, construction firms and earthquake experts. The natural disaster on the 1st of November 1755 in Lisbon was a combination of two natural disasters: A series of high and medium intensity earthquakes followed by an equally devastating Tsunami, due to the aftershock of the earthquake. The date was November 1st 1755 at 9:30 am, one of the most scared days in the Roman calendar (All Saints’ Day), thousands of devotees and followers had gathered in the innumerable streets and lanes of Lisbon crowding near Cathedrals or flocking towards the smaller churches. The day was crisp and clear and the priest had just begun chanting “Gaudeamus omnes in Domino, diem festum…” when the cathedrals and churches started to sway and lurch from side to side. The bronze bells began to ring madly and candles toppled from their stands and fell over. Within seconds from the initial ushering of the tremor, it gathered intensity and magnitude, tossing buildings down like match boxes and dislodging large chunks of masonry that fell on fearful worshippers crushing them to their death. The second larger shock came a few seconds later and caused even more damage compared to the first one, razing damaged construction and building to dust, killing thousands. After 90 minutes from the last major shock, three devastating Tsunamis struck the coast of Lisbon one after the other wiping out human settlement along the coast line and leaving nothing but indistinguishable ruins and mangled remains of construction debris and human bodies washed up on the shores. The extensive damage caused by the earthquake triggered a massive fire outbreak in the entire city, initiated by toppled candles and broken hearths, that set flame to the highly combustible wooden buildings. Soon the entire city was engulfed in the violent lashings of flame, charring to death thousands of people and leaving nothing but roasted remains of human property and burnt dead bodies. This was the horrific natural calamity in Lisbon two and a half centuries ago that killed tens of thousands of people and scarred the entire city mercilessly with irreversible damage that took centuries to rebuild. San Francisco, 1906: The San Francisco Earthquake: San Francisco was no stranger to destructive earthquakes and fires. It had burnt down 6 times during the years of gold rush in the years 1849 – 1851. This was because most of the building were made of flimsy wood and canvas thrown in together to accommodate the swelling population of the city mostly immigrants from other parts of the USA. It was the night of April 17th when the city was unaware that one of the most devastating earthquakes in the history of San Francisco would be arriving soon to throw normal life out of gear and paralyse the entire city. The streets were quite at around 5:12 am when suddenly a series of jolts rocked the city, startling the citizen from their sleep and bringing about pandemonium and chaos everywhere. It seemed as though waves were traversing along roads and highways. Waves of water surged through the streets and buildings and streets were tossed up and brought down in rapid successions. Alaska, 1964: The Alaskan Earthquake: The first super massive earthquake recorded by humanity in Lisbon, Portugal was the first one that brought this kind of a natural calamity out of the realm of superstition, from the books of fables and fairy tales into a part and parcel of day to day life. It changed the way mankind saw earthquakes forever. Again the earthquake in San Francisco in the year 1906, paved the way for what we now call as seismology and seismographic techniques to study and pinpoint earthquakes and their potential epicentres. These two were major milestones in habituating mankind to live alongside such devastating natural disasters, and rather understand the behaviour and nature of such natural upheavals. The earth quake in Alaska on Friday 27th March 1964 was quite a dramatic one, uncharacteristic of all the major earthquakes that had hit the world in different places till that point in time. Alaska back then was even more thinly populated with sparse human habitation, large open unoccupied land and just for miles together only snow capped hills and undulating terrain could be spotted. It was during the festive time of the year and it was in fact Good Friday. Quite ironically it was the day when according to the Gospel of Matthew 27:51, “and the earth shook and the rocks were split”, at Jesus’ crucifixion. The unprecedented and lurking earthquake started off with mild tremors at 5:36 pm in Alaska just when people were retiring from their work and homeward bound for the weekend and Good Friday celebrations. That meant that most of the working class was either on their way back home or were already home after a day’s work in downtown Anchorage. The businesses were done for the week and were closed down. Fishing season was also over and therefore people flocking along the coastline were also low. It was nearing spring time in Alaska with warm days and relatively cosy nights. People were not forced to stay indoors due to the extreme hard Alaskan winter but rather preferred staying outdoors. Moreover at that point of tome Alaska was having a very low population. The earthquake started as a very mild rumbling and the entire land mass supporting the city roads and buildings, in essence the entire visible land till the horizon started dancing and shaking violently. This violent shaking lasted for 5 minutes. Eye witnesses reported that it seemed to be as if it were going to last for eternity. In contrast the other earthquakes like Loma Prieta Earthquake in 1889 or the Northridge earthquake in 1994 lasted for a short burst of only 30 seconds. The damage done to the Alaska terrain, property and human construction was immense, with millions of dollars worth construction being reduced to rubble in a matter of a few minutes. The damaged caused by the Alaskan earthquake was spectacular, mostly in downtown Anchorage, where roads were buckled under the pressure due to the violent earthquake. The Alaska earthquake was not one discrete sudden jolt, rather a gradual rumble that intensified quickly to a series of shocks and back to back slips along the fault line at 19, 28, 29, 44 and 72 seconds after the initial shock. The shock waves kept getting propagated one after the other in ripples taking them almost 5 minutes to die down completely. The damage to the buildings in Anchorage was unthinkable, primarily due to the repeated jolts that rocked the Alaskan terrain. The streets were ripped open and had dropped down to 3 meters because of the land slipping beneath. Coupled with the shock waves of the earthquake, the Tsunami that followed, 10 meters in height, swept over the docks, damaging oil tankers, and reducing man made architecture, buildings etc on the shore. The Tsunami was responsible for most deaths, 122 lives out of 131. Another fatal consequence of the earthquake was the catastrophic landslide at Turnagain Heights subdivision, southeast of Anchorage. The land mass on which major developmental and construction work had started broke apart when the vigorous shaking caused the mud layers to disintegrate and liquefy along with ground water. New Madrid, Missouri, 1811 – 1812 The New Madrid earthquake: The Earthquake in New Madrid, Missouri was one of the largest earthquakes in terms of reach and intensity. The largest earthquake didn’t occur along the east coast or the west coast but rather in the centre of the continent of North America in New Madrid, Missouri. The earthquakes in New Madrid were rather a series of intense aftershocks spread across a span of 3 months. The aftershocks occurred in December 16th 1811, January 23rd 1812 and Feb 7th 1812. Due to the sparse human habitation in and round New Madrid, Missouri the loss of human lives and damage to property was minimal, but its effects on neighbouring states and cities were quite consequential. The intensity with which the earthquakes rocked New Madrid was co powerful that its effects were felt in Boston. The steeples were toppled and the church bells violently rang after the tremors in New Madrid. Though damage to buildings was minimal, the entire course of the Mississippi river was changed. The area Mississippi river from Memphis, Tennessee to Cairo, Illinois was rocked and stirred by the seismic waves originating from the cataclysmic upheaval underneath the river bed, where huge land masses crushed and slid against each other. What Causes Earthquakes? Earthquakes are caused by several reasons. They happen on subduction zone plate boundaries (Alaska), fault lines that slide horizontally (California), crush zones when continents collide due to inter-continent tectonic plate collision (Portugal, Lisbon). All these reasons are nature’s adjustment to the ever changing characteristic of the upper crust of earth’s layers of soil and landmass. The subject of modern Seismology and Seismological study starts after the shattering earthquakes in San Francisco and Alaska, that lead to the revelation that the upper crust of earth’s soil is made up of regular and irregularly shaped plates, also known as tectonic plates. The shifting and movement of these tectonic horizontally along a fault line is primarily responsible for major earthquakes having an epicentre and radiating out to the peripheries of a country or a continent. Therefore Tectonic Plate Movement is a chief cause for earthquakes. Earthquakes have been interpreted in varying and diverse ways with different mythological explanation, influenced on the tradition, beliefs and culture of the community. The fact however remains that whatever the cause of the earthquake is, it is purely coincidental to the re-arrangement of the land masses due to growing imbalances and loss of equilibrium. Cultural Explanations of earthquake: Some of the cultural explanations of causes of earthquakes by different communities and tribes across the globe are as follows: 1. The Gods were angered. According to the explanation by Portuguese people after the Lisbon earthquake. 2. Winds travelling underneath the ground. This explanation was provided by Greek Philosopher and thinker: Aristotle. 3. Giant catfish called Mamazu in Japan, This explanation is linked with Japanese mythology and folklore. 4. Dog pulling the sled stopped to scratch its back. This explanation was provided by native tribes in Serbia. 5. Arguments between the turtles that held up the earth. This explanation was provided by North American natives of the West Coast. Actual Explanations include: 1. Sudden Motion below the earth’s surface and the related vibrations that are produced from the point of origination. They propagate to the earth’s surface and are perceived as earthquakes. 2. Plate boundaries, subduction zones and transform faults are primarily responsible for earthquakes 3. Ring of fire – The pacific cusp that is in the shape of a circular rim is the most vulnerable and earthquake prone zone. It is accounted for most of the earth quakes and loss of lives due to it. It has the most seismological activity throughout the year than any other region in the whole world. Earth quake wave explanations include the following: 1. P- waves or primary waves: These waves are compression waves and are the fastest to reach. 2. S – waves, or shear waves characterised by complex waved motion. These are the second fastest to reach the earth’s surface 3. Love Waves . These are side to side waves 4. Rayleigh waves. These have wave like motion on the surface. More than 1 million detectable earthquakes happen each year. Everyday there are around hundreds of mild intensity earthquakes occurring in California regions that are too feeble to be registered by humans, it’s only the large earthquakes that claim hundreds of lives and cause extensive damage to property that we hear about on television. The rocks along the fault zone get deformed whenever there is a lack of tectonic plate equilibrium. The rocks expand, and this can be detected by changes in groundwater, electrical conductivity, magnetic field, the tilt and uplift of fault zone and other phenomena. These observations and inferences proved to be extremely vital in predicting earthquakes in China, especially the Haicheng earthquake in the year 1975. How do we measure earth quakes? The revolution of measuring earthquakes started with the idea and invention of the seismograph. This is a very sophisticated and high precision instrument that quantifies an earthquake. Earthquakes couldn’t be quantified until the invention of the seismology. Thereafter it became a possibility to measure earthquakes. Earthquakes are measured primarily in the Richter scales with values from 1.0 to 10.0 and even above. Each value in the Richter scale had amplitude 10 times greater than the previous value and 30 times more energy. Can we predict earthquakes? Predicting earthquakes is a really challenging task. No two earthquakes are the same or even remotely similar due to the very nature of interacting natural forces and properties like terrain, land mass, nature of waves, location of earthquake etc. therefore the guidelines to detect and predict an earthquake based on the data gathered from other earthquakes is most likely to lead us in the wrong direction. Rarely does it happen that two earthquakes resemble each other in terms of their causes and circumstances. As intellectually put by Charles F. Richter “Only fools and charlatans predict earthquakes”. Another challenge in the way of successful prediction of earthquake and alerting the community affected by it is the case of “Crying Wolf”. Most of the times this problem leads to a false alarm; therefore increasing the chances of the population to ignore an alarm that warns people of real earthquakes. The closest that we can get to predicting earthquakes with reasonable accuracy are finding the recurrence interval. But again, that is just the average. The Psychology of earthquakes: The very nature of the natural calamity: Earthquakes inspires and invokes extreme dread and immense fear in humans. The way an earthquake destroys life and property is the reason behind the fear that mankind bears against earthquakes. Due to the fact that earthquake’s strike with shear force and raw energy, crushing buildings, pulverising structures and razing everything to rubble, it is the most feared natural calamity. Volcanoes Volcanoes and Earthquakes are very closely related. In fact the occurrence of one leads to the occurrence of the other. Due to the very nature of and origin of the two natural calamities in several cases volcanic eruption is followed by a series of earthquakes and tremors that unsettle the earth’s crust leading to open fissures, gorges and wide chasms or channels through which molten lava (the material that fills earth’s underlying layers and crust) escapes out into open land, shooting through the atmosphere and causing extensive damage to the surrounding habitat for man and animals. It is one of the main causes of the sudden drop in temperature and an induced ice age 75, 000 years ago when there was a violent volcanic explosion leading to spewing of volcanic dust and ash hundreds of kilometers up in the atmosphere occurred in the island of Sumatra. It was responsible for a drastic drop in earth’s temperature and a near extinction of human life. Its sheer strength and magnitude can be inferred from the amount of volcanic material thrown out, a staggering 2,800 km3 volume of material. Prediction of Volcanic eruption is not an easy task. The sheer unpredictability of the activity beneath earth’s layers of soil is very challenging to understand and analyse. It is so heterogeneous and disorderly that a precise prediction of time and location of a volcanic event is really tough. Scientists and volcanologists around the globe had had some success in relating an approaching volcanic threat with other associated changes in the environment and behaviour of animals and birds apart from superficial changes in the temperature and composition of the soil. Volcanoes can be classified as: 1. Active 2. Dormant 3. Inactive or dead volcanoes Active volcanoes pose the threat of immediate eruption whereas dormant volcanoes are capable of erupting any time in the near future without posing an immediate threat in the weeks and months to come. Dead volcanoes are incapable of any eruption due to the fact that it has spent its lava and volcanic eruption in the past and now are devoid of further open channels and connectivity to earth’s interior bed of lava. Many volcanoes show signs of life with frequent fuming and spewing of smoke ash and dust, fumaroles, and sometimes even small explosions, eventually going dormant. There are different kinds of volcanic eruptions as follows: 1. Basaltic volcanoes These volcanic eruptions are composed of materials from deep underneath the earth’s surface which are several times hotter than other volcanic expulsions. These volcanic eruptions are less violent and have a lesser reach with some fountains and lava bursts. They don’t travel that far and high into the atmosphere. 2. Andesites, Dacites and Rhyolites This type of volcanic eruption is rich in silica. The remains of such volcanic eruptions are crusty and hard. They leave behind a tough terrain of hardened rocks that define the terrain and landscape in and around the eruption site. The origin of volcanic material is from the cooler magmas which are more viscous and rich in minerals. As discussed above they form thick and tough deposits. They produce pyroclastic materials, ash, pumice and hot glowing clouds of volcanic material. Sub-terrain containing such a composition of silica rich and viscous lava are the source for violent volcanic explosion. Volcanic eruptions from such sources tend to be more powerful and more explosive due to nature and structural characteristics of the chemical compounds in the lava. The eruption of Mt. St. Helens is a typical case of earthquake acting as a precursor, as a warning sign of a upcoming volcanic eruption. The earthquakes started as mild , low intensity swarms of earthquake, gradually gathering force and intensity as the volcanic eruption neared. Back in those years the absence of sophisticated volcano prediction and warning systems meant loss of several lives including that of Harry Truman owner of spirit lake lodge. The volcanic explosion of Vesuvius in AD 79 was also one of the most shattering, cataclysmic earthquakes in the history of human civilisation out of all the volcanoes recorded so far. On August 24th nature’s sudden fury was unleashed on the human habitation of Vesuvius. The entire region was covered in a thick canopy of volcanic ash, dust and pulverised rocks flying in the air and minimising visibility. The only escape route was taking to the seas. Due to lack of sufficient boats and ferries many people were left stranded and unprotected form the wrath of the aftermath of the volcanic eruption. The Vesuvius eruption led to a charging heat wave of 1560o F that charred everything in its way from humans to property to natural habitat, leaving behind a trail of unimaginable devastation and unthinkable decimation of human habitation. The city of Pompeii was buried under more than 66 feet of ash. As understood from the above discussion of specific volcanic catastrophes, it clearly bags the place of the most destructive forces of nature, a phenomena that causes agonising deaths to living creatures and instant damage to everything tangible around it. Clearly the volcano spares none. Landslides: Landslides are caused due to the loss of structural integrity of land masses and precariously positioned terrain. They are mostly experienced near river banks, waterfalls and rapids meandering through sludgy and loose soil, sea coasts and hilly terrain experience plenty of rainfall that cause the disintegration of the soil that holds together the surface of human habitation. There can be many root causes of landslides. They are the following: 1. Earthquake 2. Explosion 3. Loud Noise 4. Sources of Land and Atmospheric vibration e.g.: construction work, intensive drilling and explosion of land masses using dynamite for construction purposes. Some prime sites of landslides include regions in Malaysia, Java and Sumatra. Certain regions in hilly north east India rain fed throughout the year. As can be understood these areas have the catalyst that causes landslides: excessive fluid content in the soil, steep slopes and hilly terrain. Vaiont in 1963 witnessed one of the most terrifying landslides when the valley that was supporting millions of gallons of stored water from the river gave away due to absorption of excessive water and a consequential loss of structural integrity. This caused a mammoth 230 feet high wall of water to sweep through the city and unleash extreme destruction claiming the lives of nearly 300 people. In places like California landslides occur at slower paces without affecting human lives. It rarely cuts the path of human movement and the only reason that people get affected by it is due to bad timing and ill-fated presence during the landslide. La Conchita, California 2005 was one of the latest victims to the menace of landslides. The catalyst involved in the occurrence of the landslide was the presence of steep inclination and precariously angled slopes. The terrain was composed of marine sediments (sandstones, silt-stones and shales) that had been uplifted over 500 feet sea levels. It was a time of heavy rainfall and the land masses were heavily saturated with rainwater accumulating in the ground and underneath it. The water had saturated the sediments. On January 10th, the steep slope gave up, sending down masses of earth materials moving down the slope at a whopping speed of 22 feet per second. It ploughed through the city burying and destroying 14 houses damaging 23 others and burying dozens of people alive. As can be seen landslides have its own circumstances of destruction though localised and limited to a small region, but nevertheless causing extensive damage in the area. Conclusion: Earthquakes, volcanoes and landslides have their own means, magnitude and nature of destruction. The more dangerous out of the three being the first two, earthquakes and volcanoes cause immense widespread and damage whereas landslides are restricted to small pockets around hills, rivers, dams. Landslides on the other hand are triggered in certain cases by earthquakes. Nevertheless all three forms of natural disasters have irreversible and adverse effect on mankind and through the progress of science and technology they need to be studied deeply and avoided to the maximum extent possible. References: 1. Donald R. Prothero."Catastrophes Earthquakes, Tsunami, Tornadoes, and other earth-shattering Disasters." John Hopkins university Press. 16 Mar. 2011. Web. 1 March 2012. Read More