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Volcanoes

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Title: Volcanoes


1
Volcanoes!
  • Hi, Im Olivia and I am here to tell you all
    about volcanoes!

2
My Aims
  • The aims of the presentation is to tell you
    everything there is to know about VOLCANOES
  • The structure of the earth
  • History about volcanoes and the chosen volcano
  • Damage and after effects
  • Different types of volcanoes
  • and a conclusion
  • Also additional information will be added.

3
Mount St Helens
4
General information
  • The eruption of Mount St. Helens in Washington
    State on May 18, 1980, is certain to be
    remembered as one of the most significant
    geologic events in the United States of the 20th
    century. The explosion, on May 18, was initiated
    by an earthquake and rockslide involving one-half
    cubic mile of rock. As the summit and north slope
    slid off the volcano that morning, pressure was
    released inside the volcano - where super hot
    liquid water immediately flashed to steam. The
    northward-directed steam explosion released
    energy equivalent to 20 million tons of TNT,
    which toppled 150 square miles of forest in six
    minutes. In Spirit lake, north of the volcano, an
    enormous water wave, initiated by one-eighth
    cubic mile of rockslide debris, stripped trees
    from slopes as high as 850 feet above the
    pre-eruption water level. The total energy
    output, on May 18, was equivalent to 400 million
    tons of TNT - approximately 20,000 Hiroshima-size
    atomic bombs.

5
More information
  • On May 18 and also during later eruptions,
    critical energy thresholds were exceeded by
    potent geologic processes which were able to
    accomplish significant changes in short order.
    These processes challenge the traditional
    uniformitarian way of thinking about how the
    earth works, and serve as a miniature laboratory
    for catastrophism. Institute for Creation
    Research scientists have spent three summers
    investigating the geologic changes which have
    occurred at the volcano. Four of the most
    significant discoveries are summarized in this
    short report.

6
Local History
  • Long before settlers arrived from the east, Mt.
    St. Helens was a sacred place to the local Indian
    tribes.  They had been witnesses to its long
    history of eruptive behaviour and ancient legends
    caused them to give the mountain a wide berth. 
    Some of the names given to the mountain were
    Lawelatla ("One From Whom Smoke Comes"),
    Louwala-Clough ("Smoking Mountain"),
    Tah-one-lat-clah ("Fire Mountain") and the most
    commonly used name today Loo-wit ("Keeper of the
    Fire").  The local tribes would not fish in
    Spirit Lake, believing the fish, with heads like
    bears, held the souls of the evilest people who
    had ever lived. 

7
  • They also believed the lake shores were populated
    by a band of rogue demons.  Only young warriors
    out to prove their bravery dared climb to the
    timberline and spend the night.  Later, legends
    claimed the evil spirits of the mountain were
    punishing the local tribes for allowing the white
    men to settle at her feet.
  • In 1792, Captain George Vancouver of the British
    Royal Navy spotted the mountain from the deck of
    his ship Discovery as he sailed past the mouth of
    the Columbia River.  He gave the peak its present
    name after a fellow countryman and friend,
    Alleyne Fitzherbert, who held the title Baron St.
    Helens and was at the time the British Ambassador
    to Spain.

8
The Structure!
9
The Crust
  • This region is thin compared to the other layers
    in the Earth.  It varies in thickness from 10km
    deep to 65km deep.  The crust is made up of
    lighter rocks that "float" on top of the mantle. 
    This layer includes the continents as well as the
    rock under the oceans.  The thickness of the
    crust might be a little deceiving... to put it
    into perspective, we have built many deep mines
    but NONE have yet reached the mantle!

10
The Mantle
  • This region lies under the crust and is
    approximately 2900km thick.  The mantle is much
    denser than the crust (which is why the crust
    floats on top) and has a texture much like tar. 
    The rock in this region is rich in compounds made
    from iron, magnesium, and silicon which accounts
    for why it is denser than the crust.

11
The Core
  • This region is divided into two parts.  The outer
    part is called the Outer Core.  It is about
    2100km thick and made of liquid nickel and iron. 
    The inner part is called the Inner Core and it is
    the real centre of the Earth.  This part is about
    2800km in diameter and is made of solid iron and
    nickel.

12
Here is a more detailed drawing
13
  • earthquakes are the shaking, rolling or sudden
    shock of the earths surface. Earthquakes happen
    along "fault lines" in the earths crust.
    Earthquakes can be felt over large areas although
    they usually last less than one minute.
    Earthquakes cannot be predicted -- although
    scientists are working on it! Most of the time,
    you will notice an earthquake by the gentle
    shaking of the ground. You may notice hanging
    plants swaying or objects wobbling on shelves.
    Sometimes you may hear a low rumbling noise or
    feel a sharp jolt. A survivor of the 1906
    earthquake in San Francisco said the sensation
    was like riding a bicycle down a long flight of
    stairs.
  • he intensity of an earthquake can be measured.
    One measurement is called the Richter scale.
    Earthquakes below 4.0 on the Richter scale
    usually do not cause damage, and earthquakes
    below 2.0 usually cant be felt. Earthquakes over
    5.0 on the scale can cause damage. A magnitude
    6.0 earthquake is considered strong and a
    magnitude 7.0 is a major earthquake. The
    Northridge Earthquake, which hit Southern
    California in 1994, was magnitude 6.7.

14
  • Earthquakes are sometimes called temblors,
    quakes, shakers or seismic activity. The most
    important thing to remember during an earthquake
    is to DROP, COVER and HOLD ON. So remember to
    DROP to the floor and get under something for
    COVER and HOLD ON during the shaking.

15
Where do volcanoes occur?
16
Why do they occur?
  • Volcanic eruptions occur only in certain places
    and do not occur randomly. That's because the
    Earth's outermost shell -- the lithosphere -- is
    broken into a series of slabs known as
    lithospheric or tectonic plates. These plates are
    rigid, but they float on the hotter, softer layer
    in the Earth's mantle. There are 16 major plates.
    As the plates move about, they spread apart,
    collide, or slide past each other. Volcanoes
    occur most frequently at plate boundaries. Some
    volcanoes, like those that form the Hawaiian
    Islands, occur in the interior of plates at areas
    called hot spots. Although most of the active
    volcanoes we see on land occur where plates
    collide, the greatest number of the Earth's
    volcanoes are hidden from view, occurring on the
    ocean floor along spreading ridges.

17
  • Mount St. Helens is typical of more than 80
    percent of the volcanoes that have formed on
    land. Known as subduction zone volcanoes, they
    occur along the edges of continents where one
    plate dives, or subducts, beneath a second plate.
    When the subducting plate reaches about 100
    kilometers (60 miles) into the Earth's hot
    mantle, it triggers partial melting of the
    overlying plate and forms new magma. Some of the
    magma rises and erupts as volcanoes.

18
Pyroclastic flows
19
  • Pyroclastic flows are heavier-than-air
    gas-particle emulsions that travel across the
    ground at velocities ranging from 10 m/sec to 300
    m/sec. They can attain temperatures of over 1000
    C. They range from high density flows that move
    down valleys and can move beneath water, to
    dilute flows that extend over mountains and can
    move across water. The term "pyroclastic surge"
    is a synonym for "dilute pyroclastic flow." As
    shown by lateral facies transitions in
    pyroclastic flow deposits, pyroclastic flows and
    surges commonly develop simultaneously from the
    same flow and evolve one from the other.

20
Kilauea
  • This is a video of a fountain of lava. As you can
    see it is very hot!!!!!!

21
Mount St Helens
  • On May 18th, 1980 the eruption of Mt. St. Helens
    in southwest Washington state disrupted the lives
    of thousands and changed more than 200 square
    miles of rich forest into a grey, lifeless
    landscape. Now, twenty-four years later, the land
    around the mountain is slowly healing herself. 
    Nature is covering the scars of the eruption but
    many people will never forget what happened that
    spring day.

22
The Scorned Woman
  • May 18, 1980 dawned clear and bright.  It was an
    amazingly beautiful day for May in the Pacific
    Northwest.   Being a Sunday, there were only a
    few loggers, campers and scientists in the area. 
    Many of these people had been lulled into a false
    sense of security because of the mountain's
    recent silence.  Not even the scientists could
    predict exactly what was to come.   

23
Pictures before the eruption
24
During the Eruption
  • At 832 a.m. a 5.1 magnitude quake struck one
    mile below the mountain. While there had been
    literally hundreds of earthquakes at the mountain
    since March 20th, the unstable north face could
    not sustain another. Within moments the largest
    landslide in recorded history removed more than
    1,300 feet from the summit and swept away almost
    the entire north side of the mountain.  The
    elevation of the mountain dropped from 9,677 feet
    to its present day 8,363 feet.  What was once the
    9th highest peak in Washington state was suddenly
    reduced to the 30th highest peak. 

25
  • The intense high pressure/high temperature steam
    that escaped, instantly turned more than 70 of
    the snow and glacial ice on the mountain to
    water.  This massive movement of rock, ash, water
    and downed trees swept into Spirit Lake and down
    the north fork of the Toutle River Valley at
    speeds in excess of 175 miles per hour.
  • As the north face slid away it let loose the
    trapped gases like a cork removed from a well
    shaken bottle of champagne.  The three pictures
    below are from a series of photos taken by Gary
    Rosenquist who was camping at Bear Meadows, 11
    miles north east of the mountain. Rosenquist and
    the rest of his party survived the eruption even
    though the lateral bast was rushing straight in
    their direction at speeds nearing 650 miles per
    hour.  Luckily, after rolling over ridge after
    ridge, the blast suddenly turned.  In the last
    picture you can see the lateral blast overtaking
    the landslide.  In only three minutes the blast
    flattened 230 square miles of old growth forest
    in a fan shape north of the mountain.

26
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27
The Effects!!!
  • As the north face of the mountain collapsed,
    expanding gases and steam from the molten rock
    hurtled rock and ash out across the land at
    speeds up to 670 miles per hour uprooting trees
    as far as 6 miles from the mountain.  It was
    impossible to outrun and the searing heat too
    intense.  Reid Blackburn, a photographer with The
    Columbian newspaper was one of the first victims
    of the eruption.  Blackburn had tried to take
    shelter in his car but the lateral blast blew in
    the windows, letting in the hot, choking ash.  He
    was found in his car 7 miles north of the
    mountain.

28
  • Along with the loss of human life, it seemed the
    plants and animals in the area were almost
    completely wiped out as well. It is estimated
    that 5,000 black-tailed deer, 1,500 Roosevelt
    elk, 200 black bears, and 15 mountain goats fell
    victim. Millions of small game, fish, birds and
    insects were also in the path of the eruption. 
    The areas nearest the mountain were completely
    stripped of topsoil by the lateral blast. 
    Nothing remains but bare rock.  For weeks after
    the eruption, pyroclastic flows (seen here at
    left) of escaping steam and ash rolled down the
    remains of the north face, sterilizing the soil
    with its intense 1200 degree heat and depositing
    pumice and ash up to 60 feet thick in the valley
    below. Two weeks after the eruption when
    temperature measurements could safely be made,
    the pyroclastic deposits still averaged 650
    degrees.   Today, the pumice plan, a fan shaped
    area just below the crater, has been heavily
    eroded by wind and rain.

29
  • Directly in the path of the huge landslide was
    Spirit Lake.   Normally a chilly 42 degrees, the
    landslide instantly raised the temperature to
    near 100 degrees.  As the mud and rock hit the
    lake, the intense temperatures and choking ash
    killed all of the life in the water. Like
    dropping a large rock into a bucket of water, the
    lake sloshed up onto the surrounding hillsides,
    pulling trees and other debris into the lake. 
    With the addition of heavy metals from the
    mountain and all the organic material washed down
    from the hillsides, huge bubbles of methane gas
    escaped from the lake for months after the
    eruption.  Today the bottom of Spirit Lake is 100
    feet above the original surface.  The lake now
    has two and a half times more surface area than
    it did before the eruption.  This photo was taken
    from the top of Mt. St. Helens looking north. Mt.
    Rainier can be seen in the distance.   (photo to
    right by Lyn Topinka, USGS) The water in the lake
    looks strange because there is a gigantic mat of
    logs floating on the surface.  Today many of
    these logs have sunk or washed up on shore. 
    Plants and small animals are slowly returning to
    the water but so far the water is still not able
    to sustain larger life such as fish.

30
  • The larger portion of the landslide flowed down
    the Toutle River Valley at speeds of 30 miles an
    hour at times carrying rock (some boulders were
    as big as 20 feet in diameter), ash, trees and
    even homes downstream with it. Twenty-seven
    bridges were destroyed by the 25 foot tall wall
    of debris. By the evening of the 18th, the Army
    Corps of Engineers was forced to close the
    Columbia River at Longview, more than 75 miles
    from the mountain. The normally 40-foot deep
    channel had been reduced to 17 feet by ash
    sediment washed downstream. Even after six days
    of dredging, large freight ships could only
    navigate that section of the river during high
    tide "windows" when the channel was 30 feet
    deep.  Even now the remains of the debris
    avalanche sends enough sediment down the river
    that it is a muddy brown and towns and cities
    downstream can flood if the sediment retention
    dam can not retain enough of the silt.

31
Eyewitness Report
  • An Eyewitness Account by John H Lienhard It was a
    beautiful Sunday, morning in the Pacific
    Northwest. I left my home in Walla Walla, WA, to
    drive to Pendleton, Oregon, airport. As I drove
    south crossing the Washington-Oregon border the
    sun was rising over the Blue Mountains. It was a
    perfect day for my trip to Newark, N.J. via
    Portland and Chicago.   I was booked on United
    Airlines Flight No. 271,  scheduled to depart
    from Pendleton at 800 AM and arrive in Portland
    at 839 AM.  As I recall we were a few minutes
    late in departing.  The aircraft for the flight
    to Portland was a 727.  A few days before, Mt.
    St. Helens had given an indication of activity
    with tremors and emitting of gases.  Taking this
    in consideration, I took a window seat on the
    right side of the aircraft.  My purpose being
    that I wanted to get a good view of the mountain
    when we flew past.  There were probably no more
    than 20 to 25 passengers on board that morning.
    The flight originated in Pendleton and most of
    the passengers were to connect with other flights
    out of Portland.
  • Soon after leaving Pendleton we were flying west
    parallel to the Columbia River.  It was a bright
    and cloudless sky and the morning sun glistened
    on the snow cap mountains of the Cascade Range. 
    Somewhere in the vicinity of Mount Hood, OR our
    plane crossed over the Columbia River and
    proceeded in a westerly direction on the
    Washington side of the River. Our pilot was
    starting to descend to make the landing in
    Portland.  Looking out  the window I could see
    that we were approaching the vicinity of Mt. St.
    Helens.  Soon we were directly south of the
    mountain. The sky was very clear and an
    occasional white cloud but nothing to obstruct
    the view of the mountain.

32
  • Soon our plane was out of sight of St. Helens
    --but that cloud was parallel to our flight path.
    Our plane was on the Oregon side of the river and
    the cloud was on the Washington or north side of
    the river. As our plane continued east our pilot
    continued to comment.  He would say  "We are now
    passing Hood River and the cloud is still with
    us." Then later "We are passing The Dalles and
    the cloud is still with us."  This continued to
    be repeated until we were in the vicinity of
    Hermiston, Oregon. At that point the cloud of ash
    picked up a wind out of the southwest and it made
    a sharp turn to the north toward Tri-Cities,
    Moses Lake and Spokane, Washington.   As I
    continued to keep my itinerary and call on my
    customers,  I found myself repeating this story
    over and over.  I was questioned repeatedly about
    what I had experienced.  The interest was very
    high at the time.
  • As a point of information  As I was told on my
    arrival in the East, our flight from Portland was
    one of the last out of the Northwest on that
    Sunday. The airports were closed down and flights
    were suspended. The fine ash was entering
    aircraft, truck, automobile and locomotive
    engines and the abrasive action was causing great
    damage.
  • That is the end of my story.  I still have my
    United Airline tickets along with memories.  I
    appreciate being able to share this story.

33
  • As the plane taxied to the terminal building, I
    was making my plans for the next flight I was to
    take. I knew that to get the best view of the
    mountain I should get a seat by the window on the
    left side of the plane.  After arriving inside
    the terminal I quickly went to get my seat
    assignment on United Airline Flight 152,
    scheduled to depart at 1030 AM for Chicago.  The
    terminal was generally a quiet place that Sunday
    morning.  I talked with several people at the
    United Airline counter and none of them were
    aware of what Mt. St. Helens was doing and seemed
    very surprised.  Looking east from the terminal
    building, one could see the black cloud moving to
    the east.  It was very evident that prevailing
    winds were out of the west and thus moving the
    cloud of ash in an easterly direction.  I do not
    recall if UAL flight 152 departed on time but it
    was not delayed very long if at all.  Little did
    I realize what I would see on this leg of my
    journey.
  • As the passengers boarded and were seated, it was
    amazing to me how few of these people were aware
    of the eruption of the mountain.  Likewise, they
    were not prepared for what they would soon see. 
    After the plane was airborne and was on course to
    the east we could see the mountain.  At that time
    the pilot announced " Mt. St. Helens is erupting
    and therefore our flight plan calls for us to
    stay just south of the Columbia River and
    maintain a low altitude until we are certain that
    we are away from the cloud of ash."  The pilot
    continued to describe the eruption of Mt. St.
    Helens and indicated he would fly as close to the
    south side of the Columbia River that he
    considered safe. The mountain was belching ash
    and smoke and was very dark and eerie. There
    appeared to be lightning flashes coming from the
    crater.  The reaction of the passengers was one
    of excitement to one of no interest.  I recall
    that two ladies from Portland were sitting in my
    row of seats.  Most of the people from the other
    side of the aisle were practically on top of
    those of us on the left side so they could get a
    good view of the mountain. The two ladies were
    busy chatting away at what they were going to do
    in New York.  I asked them "Do you see the
    mountain erupting?" Their reply after viewing the
    mountain at a glance was one of amazement. "I
    have never seen a mountain do that before."  At
    the time I thought the explanation was a gross
    understatement but after thinking about it, I had
    to agree.

34
  • The pilot started to explain to the passengers
    and said "There is Mount St. Helens, she has
    been rather quiet the past few days".   At that
    point most of the passengers had moved to the
    right side of the plane to get a better view. 
    The plane was at an altitude on the decent to
    Portland airport that provide those on board UAL
    271 a view of not looking down at the mountain
    but rather out at the mountain. Although, we were
    possibly higher than the mountain peak, it
    appeared that we could almost reach out and touch
    it.  I took my eyes off of the mountain and
    leaned back in my seat.  In a matter of seconds
    the pilot shouted over the speaker "Everyone
    look quick, Mount St. Helens is making a
    spectacular display".
  • At that point, all of the passengers rushed to
    the right side of the plane and we saw an
    unbelievable sight. What had been a rather
    tranquil landscape only moments before had become
    an almost indescribable scene.  A plume of black
    ash immediately exploded from the mountain and
    went straight up into the atmosphere. I have no
    idea how high the plume went only to know that
    the ascent was very rapid.  (At a later time, a
    United Airline pilot approaching Portland from
    the south indicated it went to 90,000 ft.)  
    Simultaneously, it appeared that the westerly
    part of the mountain exploded and the area and
    sky were dark with the deep grey to charcoal
    black ash.  In a few minutes we were landing at
    the Portland airport. The sky was not a clear
    blue that was evident before the eruption but
    rather a hazy yellowish hue. There was a certain
    odour in the air that may have been a sulfur
    odour.

35
Volcanic Eruptions
  • Explosions of spatter as lava hits the ocean and
    forms a littoral cone

36
Mount Etna
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