Agenda: Tuesday April 2nd

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Agenda Tuesday April 2nd

• 1) Mental Mon(Tues)day
• 2) Hand in Geological Clocks!!!!
• 3) Volcanoes

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Phys Geo So Far

• Layers of the earth
• Continental Drift
• Tectonic Plates
• Tectonic Processes
• Geological Eras

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Still to come

• Natural disasters
• Volcanoes
• Earthquakes
• Assignment
• Rock Cycle
• Glaciation
• Soils
• Weather/Climate

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VOLCANOES!!!!
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cool fact!

• The term volcano is from the Latin Volcanus or
  Vulcan, the Roman god of fire.

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neat fact!

• The most formidable volcanoes are called
  supervolcanoes. A supervolcanic eruption can
  cause worldwide climatic changes, such as a drop
  in global temperature due to the release of tons
  of ash particles into the atmosphere. These
  monsters rear their ugly heads only ever few
  hundred thousand years, however. One of the
  biggest is in Yellowstone National Park, and
  scientists say it may be due for another eruption.

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wild fact!

• The largest volcanic eruption ever observed was
  of Mount Tambora, on the island of Sumbawa, in
  Indonesia. Its eruption in 1815 killed about
  100,000 people. Indonesia is thought to have the
  largest number of historically active volcanoes
  a total of 76, according to the U.S. Geological
  Survey.

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weird fact s

• Hundreds of years ago, the Aztecs of Mexico and
  the people of Nicaragua believed gods lived in
  lava lakes. They would sacrifice beautiful young
  girls to these powerful gods.

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sad fact ?

• During the past 400 years, nearly a quarter of a
  million people have been killed as a direct
  result of volcanic eruptions. Indirect
  aftereffects such as famine, climate change, and
  disease most likely have tripled that number

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What is a Volcano?
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A Volcano is an opening (crack) in the earths
crust where lava reaches the surface
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How are they formed?

• Volcanoes are formed when molten (sticky rock
  called magma) forces its way through a crack in
  the Earths crust.
• The magma that spills out of the crater on the
  top of the volcano is called lava.
• (lava is magma that has reached the earths
  surface)

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A lake of boiling lava on an island in the South
Pacific Ocean

• http//www.youtube.com/watch?vIAxj2ob_JoU

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Active vs. Dormant vs. Extinct

• A volcano is active when it erupts often.

• When a volcano is dormant, it has not erupted
  for a long time but it might in the future.

• A volcano is extinct when it hasnt erupted
• for at least 100,000 years.

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How does it happen?
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• We know the earths crust is made up of plates,
  and we know that these plates move

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• If you look at the location of volcanoes in
  relation to these plates, you will notice some
  things
• Many of the worlds volcanoes occur along the
  edges/ boundaries of the plates.
• Plate boundaries are among the most geologically
  active places on earth. Here, new rock is being
  both created and destroyed, so this is where most
  of the worlds volcanic eruptions and earthquakes
  occur.

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• Volcanoes are generally found where tectonic
  plates are 1) diverging or 2) converging, or from
  3)hot spots
• ..

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Sidenote

• (Volcanoes are usually not created where two
  tectonic plates slide past one another..this
  type of movement causes..???)

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Plate Tectonics Hotspots
Divergent plate boundaries
Convergent plate boundaries
Hotspots
Located away from tectonic plates, over mantle
plumes where pipes vent magma. Volcanoes formed
over hotspots become dormant and new ones are
formed when plates move overhead.
The pulling apart of plates, causing molten
rock to come to the top of the mantle. Causes
mainly submarine volcanic activity and creates
new oceanic crust.
The collision of plates, causing Subduction or
one plate to submerge beneath the other late to
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1. Divergent Plate Boundaries

• Most divergent plate boundaries are at the bottom
  of the oceans, causing most of the volcanic
  activity to be under water, thus forming new
  seafloor. (ie. Mid Atlantic Ridge)
• -Where the mid-oceanic ridge is above sea-level,
  volcanic islands are formed, for example, Iceland.

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2. Convergent Plate Boundaries

• When two plates collide, causing the one plate to
  submerge under the other plate (called
  subduction).
• In the case of oceanic-continental, a deep trench
  just off shore is formed.
• When the thick magma reaches the surface, a
  volcano is formed.
• This is what caused the typical Ring of Fire
  volcanoes.

Oceanic - Oceanic convergence
Continental - Continental convergence
Oceanic - Continental convergence
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• In the theory of plate tectonics most of the
  geological characteristics are explained by
  interaction among plates. 
• However, some of most spectacular formations are
  caused by "hot spots" which are situated far from
  the edges of tectonic plates.

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3. Hotspots
A hotspot is a place in the middle of a tectonic
plate where hot magma rises (called a mantle
plume) until it reaches the crust. Magma then
flows out.
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Pacific Ring of Fire

• The Pacific Ring of Fire is an area of frequent
  earthquakes and volcanic eruptions circling the
  basin of the Pacific Ocean.
• Result of plate tectonics and the movement and
  hitting of crustal plates.

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Pacific Ring of Fire
-The Pacific Ring of Fire is an area where large
numbers of earthquakes and volcanic eruptions
occur in a 40,000km horseshoe shape. -Contains
452 volcanoes, with over 75 of worlds active and
dormant volcanoes.
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Notes to fill in on your handout
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Inside a Volcano
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Inside a Volcano

• The magma chamber is a collection of magma inside
  the Earth, below the volcano.
• The main vent is the main outlet for the magma to
  escape.
• Secondary vents are smaller outlets through which
  magma escapes.
• The crater is created after an eruption blows the
  top off the volcano.

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There are 3 types of Volcanoes

• Shield Volcano
• Cinder Cone Volcano
• Composite Volcano

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Shield Volcano

• A gently-sloped volcano (large volcano but not
  very tall)
• Lava is thin, runny and spreads a long way from
  the vent
• 95 lava and 5 ash

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Shield Volcano Diagram
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Composite (Strato) Volcano

• Usually quite tall
• Made up of alternating layers of lava and ash
  (other volcanoes just consist of lava). Results
  in steeper sides
• Have a pyroclastic flow (a mixture of hot steam,
  ash, rock and dust).

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Composite Volcano Diagram
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Cinder Cone

• Most common
• Smallest type
• Steep, straight sides
• Often have very large summit craters
• Made of cinders (melted volcanic rock that has
  cooled down)

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Cinder Cone Volcano Diagram
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Real World Examples of Volcano Types
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What kind of volcano is this?
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Diamond Head, Hawaii is an eroded Cinder Cone
volcano

• Early sailors mistakenly thought shining
  calcite crystals inside the rocks were diamonds,
  leading to the incorrect name. Diamond Head
  formed when hot magma rising up a tube hit ocean
  water, causing large explosions that threw
  exploded magma particles into a broad ring.

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What kind of Volcano is this?
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Mount St. Helens is a composite (strato) volcano

• -Mount St. Helens (Washington) is most
  notorious for its catastrophic eruption on May
  18, 1980- the deadliest and most economically
  destructive volcanic event in the history of the
  United States.
• -an active volcano!

California
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Mt St. Helens

• https//www.youtube.com/watch?v-H_HZVY1tT4

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What kind of volcano is this?
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Kohala is a shield volcano.

• Kohala is the oldest of the volcanoes that make
  up the Island Of Hawaii. Kohala is considered to
  be extinct because it has not erupted for 60,000
  years.

Hawaii
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Positive and negative effects of an eruption
Positive Negative
-Dramatic scenery created by volcanic eruptions attracts tourists (income) -Many lives can be lost as a result of a volcanic eruption.
-Lava and ash deposited can provide valuable nutrients for the soil. Human and natural landscapes can be destroyed and changed forever.
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2010- A volcanic eruption near the Icelandic
Volcano Eyjafjallajökull glacier in southern part
of Iceland.

• http//www.youtube.com/watch?vUmEJRmBcM0o