Download NATURAL DISASTERS OF THE EARTH Earthquakes East

NATURAL DISASTERS OF THE EARTH
Read and summarize each of the four articles on Earthquakes, Mass Wasting,
Volcanoes, and Tsunamis. Be sure to explain the geologic processes that caused each
of these natural disasters.
Earthquakes East of the Rockies
Most earthquakes occur near plate boundaries in places such as California and Japan. However, areas distant from
plate boundaries are not immune, A team of seismologists estimated that the probability of a damaging earthquake
east of the Rocky Mountains during the next o years is roughly two-thirds as likely as an earthquake of comparable
strength in California. This prediction is based in part on the geographic distribution and average rate of earthquake
occurrences in these regions.
At least six major earthquakes have occurred in the central and eastern United States since colonial times, Three
were centered near the Mississippi River Valley in southeastern Missouri and had estimated Richter magnitudes of
7.5,7.3, and 7.8. Occurring over a three-month span between December 1811 and FebruaTy i8ia, these earthquakes
and numerous smaller tremors destroyed the town of New Madrid, Missouri. They also triggered massive landslides,
inflicted damages in six states, altered the course of the Mississippi River, and enlarged Tennessee’s Reelfoot Lake.
The distance over which these earthquakes were felt is truly remarkable. Chimneys were downed as far away as
Cincinnati. Hundreds of miles to the northeast, Boston residents reported
feeling the tremor. Although destruction from the New Madrid earthquakes was slight compared to the Loma Prieta
earthquake of 1989, it is only because the Midwest was sparsely populated in the early 8oos. Memphis, Tennessee,
located near the epicenter had net yet been established, and St. Louis was a small frontier town. Today, the Memphis
metropolitan area has a ponulation of more than one million people. In addition, it rests on unconsolidated floodplain
deposits, so its buildings are particularly susceptible to earthquake damage. A federal study concluded that a 7.6magnitude earthcuake in this region could cause an estimated 2500 deaths, collapse 3000 structures, cause 25
billion in damages. and disulace a u’arer of a million people.
The greatest iis r cal c -t
i the ‘astern statca occurred n Charleston South Carolina, in 1886. This one
ninute event caused o d
me ous injuru’s, and great economic loss within 200 kilometers (lao miles) of
Charleston. Mimiles after he
kp, s rong vibrations shook the upper floors of buildings in Chicago
and St. Louis,
causing people to rusS oedoor’,, in Charleston more than a hundred buildings
were destroyed, and 90 percent am the reTnalning structures were damaged.
New England and adjacert am sFr e experienced sizable shocks, including the 1683 quake in Plymouth and
the
1755 quake in Cambridge, Massachu:e Es. Since records have been kept, New York State
has experienced more than
300 earthquakes large enough o be pelt by humans. Other damaging earthquakes include one
that was centered near
Aurora, Illinois (1909), and another that shook Valentine, Texas (1931).
Earthquakes in the central ard eastern states occur far less frequently than in California. Yet shocks east of the
Rockies generally p odu e struct iral damage over larger areas than tremors of similar magnitude in California. The
reason for this difference ml ted to the underiing bedrock. In the central and eastern United States the bedrock is
older and more tig’d Sian ‘ii the ‘-‘st. As a result, seismic waves travel greater distances with less attenuation
(lessening of intensity) than :n the w”stern United States. When similar earthquakes are compared, the region of
maximum ground metiot hi he East way be up to 10 times larger than in the West. Cur sequenti the greater
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Epic Vajont Darn Disaster. Italy, 1963: Manmade or Natural?
On October 9, 1963, at 10:39 p.m., 1,000 feet of Italian Alp (specifically, Mount Toe),
consisting of about 350 million cubic yards (268 million cubic meters) of heavy compact rock,
slid northward into a vast reservoir containing 115 million cubic meters of water, The reservoir
sat behind the spectacularly tall Vajont (pronounced in English: Vay-yont) dam, which cemented
closed the west end of the Vajont Creek Valley. The mass of fallen rock completely blocked the
narrow gorge to a depth of about 1,200 feet just behind the dam.
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This amazing landslide took between 20 and 30 seconds to displace more than 50% of the
reservo’r’s water by first creating a giant wave of about 40,500 acre$eet (50 million cubic
meters, The wave rose up as a mushroom to 820 feet (250 meters) in height, and then, in a 50
million-cubic meter tsunami rush, powered 25 million cubic meters of smelly water both
upstream (eastward) to smash two small villages named Casso and Erto. and downstream
(westward) over the top of the dam to crush five towns (Longarone, Pirago. Villanova, Rivalta,
and Fae) in the valley of the Piave River. The entire upstream and downstream inundation
occurred in less than seven minutes. One cubic meter of water weighs 2.200 pounds. The Vajont
dam itself was unharmed
About 2,000 (some sources say 2 600) people perished in this unusual disaster, and about 1,300
f the atalitc occurre in the t w of Lo garone (proince of Belluno resulting in a fatality
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s on 0 ‘t th r 10, 1963, stood on br dg s in thc a cy of the iave
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Rer uith oles deseratel wnKin o hook the bodies of burr ans and ammals floating by to
pre’ cut the’r ‘aterr trinsnort on mies to the Adriatic Sea near the city of Venice. Economic
losses have never been definitieiv issessed as a result of litigation h plaintiffs, particularly
Onc c-f the nrernses of the piantiti that the disaster
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The Eruption of Mt St Helens
The eruption of Mt. St. Helens in 1980 was the worst volcanic disaster in U.S. history;
however, it offered scientists an exceptional opportunity to examine and study a large
volcanic eruption, which has enriched scientific knowledge of volcanoes.
Mt. St. Helens is a composite volcano within the Cascade Range in what is now southern
Washington, approximately 50 miles northwest of Portland, Oregon. Though Mt. St. Helens
is approximately 40,000-years old, it is considered a relatively young, active volcano.
Mt. St. Helens historicaHy has had four extended periods of volcanic activity (each lasting
hundreds of years), interspersed with dormant periods (often lasting thousands of years).
The volcano is currently in one of its active periods.
Native Amencans hying in the area have long known that this was not an ord nary
mountain, but one that had fiery potential. Even the name, “Louwala-Clough, a Native
American name for the volcano, means “smoking mountain.
Native Americans living in the area have long known that this was not an ordinary
mountain, but one that had fiery potential. Even the name, “Louwala-Clough a Native
American name for the volcano, means “smoking mountain.”
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The volcano was first discovered by Europeans when British Commander George Vancouve
of the H,M.S.Discovery spotted Mt. St. Helens from the deck of hs ship while he was
exploring the northern Pacific Coast from 1792 to 1794. Commande- Vancouver named toe
mountain after F s eIlow countryman Aileyne Fitzherhert, the Baron St, Heiens, vh vc
servra a the BrLsh arobacador to Scam.
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Similar eruptions to the one on March 27 continued for the next month. Though some
pressure was being released, large amounts were still building.
In April, a large bulge was noticed on the north face of the volcano. The bulge grew quickly,
pushing outward about five feet a day. Though the bulge had reached a mile in length by
the end of April, the plentiful plumes of smoke and seismic activity had begun to dissipate.
Thus, as April drew to a close, officials were finding it increasingly difficult to maintain the
evacuation orders and road closures due to pressures from homeowners and the media as
well as from stretched budget issues.
At 8:32 a.m. on May 18, 1980, a 5.1 magnitude earthquake struck under Mt. St. Helens.
Within ten seconds, the bulge and surrounding area fell away in a gigantic, rock avalanche.
The avalanche created a gap in the mountain, allowing the release of pent-up pressure that
erupted laterally in a huge blast of pumice and ash. The noise from the blast was heard as
far away as Montana and California; however, those close to Mt. St. Helens reported hearing
nothing.
The avalanche, huge to begin with, quickly grew in size as it crashed down the mountain,
traveling around 70 to 150 miles per hour and destroying everything in its path. The blast of
pumice and ash traveled northward at 300 miles per hour and was a raging hot 660° F
(350° C). The blast killed everything in a 200-square mile area. Within ten minutes, the
plume of ash had reached 10 miles high. The eruption lasted nine hours.
For the scientists and others who were caught in the area, there was no way to outrun
either the avalanche or the blast. Fifty-seven people were killed. it is estimated that about
7,000 large animals such as deer, elk, and bears were killed and thousands, if not hundreds
of thousands, of small animals died from the volcanic eruption.
Mt. St. Helens had been surrounded by a lush forest of coniferous trees and numerous clear
lakes before the blast. The eruption felled entire forests, leaving only burned tree trunks all
flattened in the same direction. The amount of timber destroyed was enough to build about
300,000 two-bedroom homes. A river of mud traveled down the mountain, caused by
melted snow and released groundwater, destroying approximately 200 houses, clogging up
shipping channels in the Columbia River, and contaminating the beautiful lakes and creeks
in the area.
Mt. St. Helens is now only 8,363-feet tall, 1,314-feet shorter than it was before the
explosion. Though this explosion was devastating, it will certainly not be the last eruption
from this very active volcano.
The Deadliest Tsunami in History?
Tsunamis: Facts About Killer Waves
The earthquake that generated the great Indian Ocean tsunami of 2004 is estimated to have
released the energy of 23,000 Hiroshimatype atomic bombs, according to the U.S. Geological
Survey (USGS>.
Giant forces that had been building up deep in the Earth for hundreds of years were released
suddenly on December 26, shaking the ground violently and unleashing a series of killer waves
that sped across the Indian Ocean at the speed of a jet airliner.
By the end of the day more than 150,000 people were dead or missing and millions more were
homeless in 11 countries, making it perhaps the most destructive tsunami in history.
The epicenter of the 9.0 magnitude quake was under the Indian Ocean near the west coast of
the Indonesian island of Sumatra, according to the USGS, which monitors earthquakes
worldwide. The violent movement of sections of the Earth’s crust, known as tectonic plates,
displaced an enormous amount of water, sending powerful shock waves in every direction.
The earthquake was the result of the sliding of the portion of the Earth’s crust known as the
India plate under the section called the Burma plate. The process has been going on for
millennia, one plate pushing against the other until something has to give. The result on
December 26 was a rupture the USGS estimates was more than 600 miles (1,000 kilometers)
ong, displacing the seafloor above the rupture by perhaps 10 yards (about 10 meters>
horizontally and several yards vertically. That doesn’t sound like much, but the thilions of tons
of rock that were moved along hundreds of miles caused the planet to shudder with the largest
magnitude earthquake in 40 years.
Above the disturbed seafloor the great volume of the ocean was displaced along the line of the
rupture, creating one of nature’s most deadly phenomena: a tsunami, Within hours killer waves
radiating from the earthquake zone slammed into the coastline of 11 Indian Ocean countries,
snatching people out to sea, drowning others in their homes or on beaches, and demolishing
property from Africa to Thailand.
Tsunamis have been relatively rare in the Indian Ocean, at least in human memory, They are
most prevalent in the Pacific. But every ocean has generated the scourges. Many countries are
at risk.
The Indian Ocean tsunami traveled as much as 3000 miles (nearly 5000 kilometers) to Africa,
arriving with sufficient force to kill people and destroy property.
A tsunama may be ass than a foot (30 centimeters) n height on the surface of the open ocean,
which is why they are not noticed by 5811015. But the powerful pulse of energy travels rapidly
through the o.cean at hundreds of miles per flour Once a tsunami reaches shallow water near
the coast it ‘s slowed down. The top of the wave moves faster than the boom, causing the sea
to rise dramatIcally.
The indian Ocean tsunami caused waves as high as 50 feet (15 meters) P some places.
according to news renorts. But in many other pieces wttnesses descrIbed a rapId surgIng of the
ocean, more like an extremely powerful river or a flood than the advance and retreat of giant
waves.
Tsunamis can extend inland by a thousand feet (300 meters) or more. The enormous force
and weight of so much water sweeps away almost everything in its path. As many as a third of
the people who died in the Indian Ocean tsunami were children; many of them would not have
been strong enough to resist the force of the water. Many people were crushed by debris or
when the sea hurled them against structures.
Witnesses said the approaching tsunami sounded like three freight trains or the roar of a jet. In
some places the tsunami advanced as a torrent of foaming water.
In several places the tsunami announced itself in the form of a rapidly receding ocean. Many
reports quoted survivors saying how they had never seen the sea withdraw such a distance,
exposing seafloor never seen before, stranding fish and boats on the sand. Tragically the
novelty of the sight apparently stoked the curiosity of the people who ran out onto the exposed
seafloor. Tourists in Thailand were seen wandering around photographing the scene.
Geographic Knowledge Saved Lives
People who knew geography knew what the receding ocean meant Survivors who knew it
meant trouble reported how they ran for high ground, rounded up family and friends, and tried
to warn people who were drawn to the water’s edge. Experts say that a receding ocean may
give people as much as five minutes’ warning to escape to high ground. That may have been
enough time for many of the people who were killed by the 2004 tsunami to save themselves, if
only they knew what to do.
A British newspaper reported that a school student, on vacation in Thailand, recalled a
geography lesson about tsunamis and what the withdrawal of the ocean meant She warned
her family and they saved themselves.
in india a man told the Associated Press how he saved his village of some 1 500 people
because he recalled watching a National Geographic television documentary about tsunamis
[Killer Wave], and remembered that when the ocean receded it was a sign of danger. He
sounded the alarm and led the people to high ground, saving almost the entire village.
Somehow the animals also seemed to know that disaster was imminent. Many people reported
that they saw animals fleeing for high ground minutes before the tsunami arrived. Very few
animal bodies were found afterwards,
When the ocean started to return on December 26 it was in the form of the tsunami—a series
of crashing waves in some places and a sudden flood hundreds of yards inland in others.
Reports quoted survivors saying they could not run away fast enough. although many people
did manage to escape.
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d mty eople h
he to rent Some urvi ed others
safely or a mall ess.
etc ooethe whe th t ur cmi st ck were separated
ccurr ed or disapoear
baby was to nd floatirg
Survivors of the lndan Ocea9 tsunami reported that the sea suroed out as fast and as
powerfuly as t came ashore Mary neople who had survived the wail o water rushing Iniand
vere se being swept ou to sea wt en tho ocean etr ated
tsu m s a e s of a s a d e firs
ye ay ot a i most danger s. tsur
wave rain ma come as surges fve minutes to an our apa The cy e may be marked by
mceateo retreat and dvance of the ocean. Some OCOPiC da ot knew This or. Deembe 26
Qroe the rst wave ned gnre they thought it wns safe to qo nown o the beacf
The Indian Ocean tsunami destroyed thousands of miles of coastline and even submerged
entire islands permanently. The island country Maldives rises only a few feet above sea level,
but it is largely protected by outlying coral reefs. Even so, the tsunami swept across the reefs
and was reported to have washed over some islands entirely. The capital and many tourist
resorts in the Maldives were flooded. Astonishingly, relatively few people were killed. The
country was likely protected from the full force of the tsunami by its reefs.
Rotting Corpses
As the day of horror drew to a close the ocean calmed, But where at the start of the day people
were going about their normal lives or relaxing at exotic beach resorts now millions of people
were struggling with the reality of tens of thousands of dead or missing relatives, destroyed
homes, and shattered lives. The thousands of corpses, many hanging in trees or washed up
on beaches, immediately started to rot in the tropical heat With no food or clean water and
open wounds, the risk of famine and epidemic diseases was high. Health authorities feared
that the death toll might double to 300,000.
Across the world the magnitude of the disaster and the scale of the suffering prompted a new
wave—one of sympathy, support, and assistance for the people affected by the tsunami.
Deep beneath the ocean, at the source of the great earthquake and tsunami, the Earth’s
tectonic plates continued their relentless pressing against one another. Pressure was already
building for the day when pent-up energy will once again be released violently—but hopefully
not for hundreds of years.
Adaoted from: http://news.natonalgeogrphc cornnews/pf/6S467352.html
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