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Chapter 8
Volcanoes
Science Entry 2
Objectives
chapter 8
• I will know the difference between non
explosive and explosive volcanic eruptions.
• I will explain how the composition of magma
determines they type of volcanic eruption tat
will occur.
• I will know what the main types of lava and
volcanic debris there is.
Entry 2
Science Vocabulary
Remember if you want an extra point you can
create a word wall. Please see me afterschool or
email which word you would like. You can only do
one word.
• Magma
• Vent
• Lava
• Volcano
• Pyroclastic material
Entry 3
Nonexplosive Eruptions
• Lava flows come from non
explosive eruptions.
Relatively calm outpourings
of lava
• Huge outpouring of molten
rock
• Mountains can form over
hundreds of thousands of
years.
Entry 4
• Science vocabulary homework
Entry 5
Explosive Eruptions
• Clouds of hot debris and gases
shoot out
• Sometimes at supersonic speed.
• Molten rock blown into a
million of pieces that harden in
the air.
• Blast millions of tons of solid
rock from a volcano.
• In minutes an explosive
eruption can demolish rock
formations that took thousands
of years to form.
• A volcano may shrink in size
after repeated explosive
eruptions.
Entry 6
Magma
• Magma- hot, liquid material that
creates volcanoes
• Magma collects in magma
chambers . Magma rises through
the holes in the Earths crust called
vents.
• Magma that erupts and flows on
the Earth’s surface is called lava.
• Magma that erupts as fragments of
molten material that solidly in the
air is called pyroclastic material.
Entry 7 Water Magma
• Water- a volcano can have
higher chances of
erupting explosively if
magma has a high water
content.
• Like a can of soda , when
you shake the can up. The
more water magma
contains the more
pressure it creates.
Entry 8 Silica Magma
• A high quantity of silica
(mineral) found in magma
can cause major explosions.
• Silica rich magma has a
thick, stiff consistency. It
flows slowly and tends to
harden in the volcano's vent.
• This plugs the vent,
producing pressure.
• Lower amounts of silica
results in calmer eruptions.
Entry 9: What erupts from a volcano?
• Depending on how explosive a
volcanic eruption is, magma erupts
as either lava or pyroclastic
material.
• Non explosive eruptions produce
mostly lava
• Explosive eruptions produce mostly
pyroclastic material.
• Over years a volcano can have
explosive and non explosive
eruptions.
• In a single eruption a volcano may
have both non explosive and
explosive eruptions.
Entry ___
What is Lava?
• Lava is magma that flows onto
the Earth’s surface.
• Once magma erupts and flows
onto earth’s surface it is lava.
• Lava can be thick or thin.
Entry ____
Types of Lava
Blocky Lava
• Blocky Lava - is cool, stiff lava
that cannot travel far from the
erupting vent.
• Blocky lava oozes from a volcano
ONLY after an explosive eruption
has released much of the gas
pressure from the magma
chamber.
• After it cools, blocky lava forms
jumbled heaps of sharp-edged
chunks.
Entry ___
Aa lava
• “Aa” lava is a Hawaiian word
that refers to a type of lava
that has a jagged surface.
• The stiff lava pours out
quickly and forms a brittle
crust.
• Crust is torn into jagged
pieces as the molten lava
under it continues to flow.
Entry ___
Pillow Lava
• Forms when lava erupts
underwater.
• Forms rounded lumps
that are the size and
shape of pillows.
• Pillows lava has a rounded
shape because contact
with water causes fast
cooling.
Entry ___
Your turn!
• Sketch in this entry the three types of lava.
Label them and draw them into this entry. I
will be checking it this week.
Pyroclastic Material Entry 15
• Rock fragments created by explosive volcanic
eruptions.
• Produced when magma explodes form a
volcano and solidifies in the air.
• Also produced when existing rock is shattered
by powerful eruptions.
• A variety of sizes, from boulders the size of
houses to particles so small in atmosphere.
Entry 16 Pyroclastic Material Types
• Volcanic blocks – the largest piece of
pyroclastic material. Consist of solid rock
blasted out of volcanoes.
• Volcanic bombs- large blobs of magma that
harden in the air.
• Lapilli- “little stones” in Italian. Pebble like bits
of pyroclastic material.
• Volcanic Ash- particles that are less than 2 m
in diameter.
Entry 17
Chap. 8. Section 2
Volcanic Effects on Earth
• Objectives
• I will describe the effects that volcanoes have
on Earth.
• I will compare the different types of volcanoes
Entry 18
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Vocabulary
1. Shield Volcano
2. cinder cone volcano
3. composite volcano
4. crater
5. caldera
Effects on Earth Entry 19
• Explosive Impact Effects
• - Because it is thrown high in the
air, ash ejected during explosive
volcanic eruptions can block out
the sun for days . Ash can blow
down trees and buildings. Cover
towns in blankets of ash.
• Flows- Clouds of hot ash can
flow rapidly downhill like an
avalanche, choking and searing
all living things. Mudflows can
create rivers of ash
Entry 20
Fallout Effects on Earth
• As volcanic ash falls to the ground,
the effects can be devastating.
Buildings may collapse under the
weight of so mush ash.
• Ash can dam up river valleys,
resulting in massive floods.
• Too much ash can smother crops,
causing food shortages and loss of
livestock.
Entry 21 Climatic Fluctuation
• In large eruptions, volcanic ash, along with sulfur
rich gases, can reach the upper atmosphere. As
the ash and gases spread around the globe they
can block out enough sunlight to cause the
average global surface temperature. To drop.
• This temperature drop can last for years, bringing
wetter, milder summers and longer, harsher
winters.
• This can cause food shortages that result in
starvation and disease.
Entry 22 Shield Volcanoes
• Shield Volcano – build out
of layers of lave from
repeated non explosive
eruptions. Because the lava
is very runny, it spreads out
over a wide area. Over time
the layers of lava create a
volcano with gently sloping
sides. Although their sides
are not very steep, shield
volcanoes can be
enormous. .
Entry 23
Cinder Cone Volcanoes
• Small volcanic cones made
entirely of pyroclastic material
from moderate explosive
eruption. The pyroclastic
material forms steeper slopes
with a narrower base than the
lava flows of shield volcanoes.
Usually erupt for only a short
time and often occur in
clusters. They erode quickly.
Entry 24
Composite volcanoes
• Also known as
stratovolcanoes, most
common types of volcanoes.
They are formed by explosive
eruptions of pyroclastic
material followed by quieter
outpourings of lava. This
creates alternating layers of
pyroclastic material and lava.
They have broad bases and
sides that get steeper toward
the summit.
Entry 25 Craters and Calderas
• Crater- top of the central vent in most
volcanoes is a funnel shaped pit
• A crater’s funnel shape results form
explosions of material out of the vent
as well as the collapse of material from
the crater’s rim back into the vent.
• Caldera- forms when a magma
chamber that supplies material to a
volcano empties and it’s roof
collapses. Causing the ground to sink,
leaving a large, circular depression.
Entry 26
Lava Plateaus
• Most of the lava on Earth’s continents erupts
for long cracks, or fissures, in the crust. When
it runs for a long period of time the landform
is known as lava plateau