Transcript volcano - Mrs. Henderson

Do First
Actions: Turn in Volcano vs Earthquake Webquest
Questions:
1. What type of plate interaction(s) forms volcanos?
2. What type of plate interaction(s) does not form volcanos?
Boys rules still apply, hop up and get 30 minutes with me
Agenda
• Test is Wednesday: Plate Tectonics, Earthquakes, and Volcanos
• Volcano Notes
• Volcano Video
Pixar Video
https://www.youtube.com/watch?v=uh4dTLJ9q9o
What is a volcano?
• A volcano is a rupture on the crust that
allows hot lava, volcanic ash, and gases to
escape from a magma chamber below the
surface
Where do Volcanos occur?
•Volcanos mostly occur at convergent and
divergent plate boundaries
•Plate motion causes mantle rocks to melt to
form magma
What causes volcanoes?
Where do Volcanos occur?
•Convergent boundaries produce volcanic arcs
• At Ocean – ocean convergent boundaries rising
magma can form volcanic arcs in an ocean
(Aleutian Islands).
• At Ocean – continental boundaries rising magma
can form continental volcanic arcs (Andes
Mountains).
• 75% of volcanos occur in the “Ring of Fire”
•Divergent boundaries produce the greatest
volume of volcanic rock along the oceanic
ridge system
Where do Volcanos occur?
•The remaining volcanos occur within a plate
and not at a boundary which is called
intraplate volcanism
• The regions are known as “hot spots”
• Volcanos occur here because a mass of hotter than
normal mantle material called a mantle plume rises
toward the surface.
• The Pacific plate moves over a hot spot, producing the
Hawaiian Islands.
Mantle Convection Models
Hot Spots
Types of Eruptions
•Violent (Explosive)
• Destroy the volcano
• Viscous (thick) lava traps the gases until large
pressures build up & the system explodes
• Pyroclastic flow (ash, rock fragments) flow out of
vent
•Non-violent (Calm or Quiet)
• Build up the volcano
• Fluid lava flows easily allows gases to bubble away
Types of Lava
•Lava is what magma is referred to once it
reaches the surface
•Viscous Lava (Thick)
• Cool temperature
• Composition: silica-rich (granitic)
•Fluid Lava (Thin)
• Higher temperatures
• Composition: Low silica (basaltic)
Other Ejected Materials
•Dissolved gases
• Mainly water vapor and carbon dioxide
• If gases escape easily then eruption is less explosive
• Pyroclastic Materials
• particles produced in volcanic eruptions
• Range in size from very fine duct and volcanic ash (less
than 2 millimeters) to pieces that weigh several tons
Pompeii
After the 79 C.E. eruption
Parts of a Volcano
• A volcano is a mountain formed of lava and/or pyroclastic
material.
• A crater is the depression at the summit of a volcano or that
which is produced by a meteorite impact.
• A conduit, or pipe, carries gas-rich magma to the surface.
Types of Volcanos
Shield volcano
Composite volcano
Cinder cone volcano
Types of Volcanos
• The three main volcanic types are shield volcanoes,
cinder cones, and composite cones.
Types of Volcanos
•Shield Volcanoes
• Shield volcanoes are broad, gently sloping volcanoes built
from fluid lavas.
Types of Volcanos
• Cinder Cones
• Cinder cones are small volcanoes built primarily of pyroclastic material
ejected from a single vent
• Steep slope angle
• Rather small in size
• Frequently occur in groups
Types of Volcanos
• Composite Cones
• Composite cones are volcanoes composed of both lava flows and
pyroclastic material.
• Large size
• Alternating layers of lavas and pyroclastics
• Most violent type of activity
Types of Volcanos
•Volcanos can also be defined by when they
are expected to erupt
• Active: has erupted in the last 10,000 years
• Dormant: hasn’t erupted in the last 10,000 years
but it expected to erupt again
• Extinct: hasn’t erupted in the last 10,000 years
and is not expected to erupt again
Mount St. Helens Before and
After the May 18, 1980, Eruption
https://www.youtube.com/watch?v=UK--hvgP2uY
DYL
• 1. What are the three types of volcanos?
• 2. What is a hot spot?