Download What IS A VOLCANO?

How do volcanoes affect the lithosphere,
plate boundaries, & the atmosphere?
VOLCANOES
Unit 5
EEn.2.1.1
How do volcanoes affect the lithosphere,
plate boundaries, & the atmosphere?
A volcano is a place
where lava reaches
the surface.
- The Vents - is the
main conduit through
which magma moves
towards to get to the
surface.
The Crater - sits at the
top of a volcano and is
the location where much
of the lava, gas, rock
fragments and ash are
ejected from.
There are three types of Volcanoes
1. Shield Volcano:
A gently-sloped
mountain. Forms
when layers of
basaltic lava
accumulates during
nonexplosive
eruptions.
2. Cinder Cone:
A volcano made of cinders
that are blown into the air.
•
•
•
Are smaller
volcanoes
Its magma consists
of more water &
silica than what is
found in shield
volcanoes
Large amounts
of gas
3. Composite:
A volcano built of alternating layers of
cinders and lava.
• Composite
magma consists
of large amounts
of silica, water,
and gases.
• Are more
violently
explosive
Mount Shasta is a composite
volcano.
Over the last 10,000
years, Mt. Shasta
has erupted on
average once every
800 years. During
the 3,500 years the
volcano has erupted
about once every
300 years.
Diamond Head is an eroded Cinder (Tuff)
Cone.
Diamond Head
formed when hot
magma rising up a
conduit hit ocean
water, causing large
explosions that
threw exploded
magma particles
(tuff) into a broad
ring.
Compare Magma & Lava
Magma is molten rock which is still underground in
vents. On the other hand, lava refers to molten rock
which has found its way to the ground after an
eruption.
Lava occurs in active volcano while magma occurs in
an inactive one. At the core of the earth is hot
molten rock, magma. The molten rocks erupt
through a volcano and come out as lava. The
temperature of magma is extremely high while that
of lava are lower as it cools down when it comes
out under the atmosphere. The varying amount of
heat causes a difference in their viscosity; magma's
viscosity is lower due to immense heat inside earth.
What are Lahar?
• Lahar is an Indonesian term that describes a
hot or cold mixture of water and rock
fragments flowing down the slopes of a
volcano and (or) river valleys. It’s mud.
When moving, a lahar looks like a mass of
wet concrete that carries rock debris ranging
in size from clay to boulders.
• Can lead to increased deposition (sediments
on the ground/bottom of a body of water) of
sediments
• Can destroy streams, valleys, &
communities
What are Lahar?
Volcanic effects on lithosphere, & plate
boundaries
Convergent plate boundaries are
locations where lithospheric plates
are moving towards one another. The
plate collisions that occur in these
areas can produce earthquakes,
volcanic activity and crustal
deformation. This results in
destruction of the lithosphere.
Volcanic effects on lithosphere, & plate
boundaries
Convergent Plate Boundary Oceanic and Continental
Plates
The buoyant magma
chambers begin a slow
ascent through the overlying
materials, melting and
fracturing their way
upwards. If a magma
chamber rises to the surface
without solidifying, the
magma will break through in
the form of a volcanic
eruption. This will destroy
the oceanic lithosphere.
Volcanic effects on lithosphere, & plate
boundaries
Convergent Plate
Boundary - Oceanic
When a convergent boundary
occurs between two oceanic
plates one of those plates will
subduct beneath the other.
Normally the older plate will
subduct because of its higher
density. Magma begins
ascending by melting and
fracturing its way through the
overlying rock material.
Magma break through to form
a volcanic eruption cone.