Transcript Volcanoes - Cloudfront.net

Chapter 8
VOLCANOES
1
How do volcanoes form?
When magma (melted rock) gets to
Earth’s surface, it erupts and forms a
volcano.
Ring of Fire – the
area that many
volcanoes are
located by the plate
boundary in the
pacific ocean.
Where do volcanoes form?
Most volcanoes form at plate boundaries.
Divergent
Boundaries
summary
picture
Convergent
Boundaries
summary
picture
Magma
Plumes/Hot
Spots
summary
picture
Hot Spots
A volcanically active area that is not near a
tectonic plate boundary
4
What causes magma to form?
Magma needs 3 things:
Temperature•Rock has to get
really hot to melt
•High
temperature
Pressure•Low pressure
•This is found
near the crust
•Magma takes
up more space
than rock.
Fluid•Rock that has
fluids like water
can melt more
easily than dry
rock
5
Review 8.1
•Hot spot
•Magma
•Volcano
•Divergent boundary
•Convergent boundary
•Subduction
•Locations of volcanoes
•How magma forms
•How rock melts
•Mid-ocean ridge
What kind of volcanoes form at
Divergent boundaries?
Mid Ocean Ridge
•Mafic lava – thin, runny, dark
•When lava erupts under the water it hardens quickly
New land
Old land
Oceanic
crust
magma
Sea floor spreading
Oceanic
crust
Old land
Rift zone – deep cracks that form as two plates
separate.
What kind of volcanoes form at
convergent
boundaries?
Lava
• comes from melted crust and melted mantle
• mafic (rich in magnesium and iron) (thin, dark,
runny)
•felisc (rich in silica and feldspar)(thick, sticky, light in
color)
Pyroclastic
material – rocks,
gas, ashes, large
chunks
Big explosion
Pyroclastic flow
•Can destroy everything in its path
•700 degrees C super HOT!!
Vent – openings where lava is
released.
Magma chamber – the magma
that feeds the eruption pools
deep underground in this
structure.
Lava tubes- long pipelike
structures created when the
flow will cool and solidify on
top while the interior continues
to travel.
9
Types of Lava
1. Lava – magma that has reached earth’s surface.
•Thin and runny, like water
•Thick and stiff
•Made of different material
2. Mafic – magma that comes from the mantle
•Lava that has a lot of iron and magnesium
•Not much silica
•Dark in color
Shield volcano
• Lava quietly flows from the vent.
• mountain covers a large area.
• sides are gently sloped.
• Mountain is dome-shaped.
• wide tall mountain.
• mafic lava – runny and dark.
• Erupts over and over for a long period of time.
• continuous non explosive eruptions.
Cinder cone volcano
• cinders and rock particles are blown into the air.
• Mountain is small.
• Mountain has steep sides.
• lava and ash come out of small vents and spray
out in the air. Pieces of hard lava fall on the
ground (cinders).
• cinders and ash build
up around the vent to
form a small, steep
volcano
• Example: Paricutin, Mexico
Composite volcano
• violent eruptions sends up volcanic bombs,
cinders and ash.
• quiet volcanic flow follows the explosion. Alternating
layers continue forming the mountain.
• mountain is large.
• Sides steep.
• mountain is cone-shaped.
• Erupts over and over for
a long period of time.
• also called strato
volcano.
• Example: Mt. Vesuvius,
Italy.
Review 8.2
•Lava
•Rift zone
•Mantle chamber
•Pyroclasitc material
•Mafic
•Felsic
•Shield volcano
•Composite volcano
14
Effects of volcanic eruptions
Harmful
•Volcanoes hurt/kill people
•Destroys buildings and trees
•Creates changes in the environment
•Pyroclastic flows bury anything in its path.
•Snow and rain can cause floods and mudflows
(lahars).
•Hard to breathe
•Damages crops
•Ashes can block sunlight and make the world cooler
for several years.
•Affect Earth’s climate for several years.
•Ash and gases released in the air can cause
temperatures to go down.
Effects of volcanic eruptions
Helpful (benefits)
•Volcanic rocks break down soil
•Volcanic Soil contains nutrients for plant growth.
•Geothermal energy – people can pump hot water
out of rocks to make electricity or to heat
buildings.
•Volcanic rocks –used for build buildings, cat
litter, soap, cleaners, and polishes
Review 8.3
•Lahar
•Geothermal water
•Volcanic soil
•Global effect of volcanic eruption
•Uses of volcanic rocks.
•Geothermal energy.
•Large volcanic eruptions can cause…