Volcanoes
Week 2
December 7 to December 11
1
Wk. 2 Day 1
• Before: Question of the Day
– What 3 factors control the style of a volcanic eruptions?
• During: Notes
• After: Exit Slip
2
Three Types of Volcanoes
1. Shield
2. Cone
3. Composite
3
Volcanoes
• Shield Volcano: A broad volcano with
gently sloping sides, quiet eruptions,
silica-poor lava. (ex. Hawaiian Islands)
4
Shield ( Basic) Cone
Mauna Loa Hawaii -USA
Shield Volcanoes are enormous features
built up only from layers of lava. They
produce lots of lava but they tend not to
erupt violently.
Layers of Lava
Lava Flow
10,000m
250 miles
Composite volcano to scale
Volcanoes
• Cinder Cone Volcano: steep sided
volcano, explosive eruptions that
throw lava and rock in the air, silicarich lava (ex. Paricutin in Mexico)
6
Ash and Cinder Cone
Paracutin - Mexico
Volcanic Bombs
3,000m
Pipe
The volcano is built
up of layers of ASH.
When it erupts it is
normally with great
explosive force.
Layers of Ash
and Cinder
Volcanoes
• Composite Volcano: a small volcano, both
quiet and violent eruptions
• (ex. Mt. St. Helens)
• Also called “stratocones”
8
Composite Cone
Mt St Helens - USA
Crater
Pyroclastic Flow
The volcano is built up
of alternate layers of
LAVA and ASH. They can
explode with great
violence.
Ash layer
Lava Layer
Conelet
Dyke
Flank
eruption
Lava
Flow
Crust
Volcanic (lava) Domes
• A volcanic dome is created when a body of
viscous lava slowly pushes its way upward.
• An example is the Dome formed in crater
left by 1980 eruption (explosion) of Mount
St. Helens.
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Lava Dome
11
Volcanoes
• Tephra: pieces of rock and solidified lava that
fall from the air. (all types of pyroclastic
material)
• Lahar: a mixture of water , pyroclastic
material, sand , and gravel capable of moving
up to 100 km/hr (mudflow)
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Volcanic Mud Flow (Lahar)
13
14
Wk. 2 Day 2
• Before: Question of the Day
– What are the three type of volcanoes?
• During: Notes
• After: 3-2-1
15
Pyroclastic Material
Ash, Lapilli, Lava Bombs
There are many kinds of pyroclastic material ejected during a volcanic eruption.
Ash
Ash is the most common pyroclastic rock material ejected during an eruption.
Volcanic ash is so fine that it can be blown into the atmosphere and picked up by
the jet stream where it can circle the Earth for several years.
Lapilli
Lapilli are pea-size to walnut-sized pieces of volcanic rock. All types of lava
produces lapilli. Shield volcanoes, cinder cones, and composite volcanoes all
produce lapilli
Lava bombs
Lava bombs are volcanic rocks larger than 64 mm in size. Lava bombs leave a
volcano vent as glowing semi-molten rock fragments. While airborne lava bombs
become streamlined forming aerodynamic shapes.
16
Violent volcanic eruptions
Lava blocks are often produced during violent volcanic eruptions when pieces
of a volcano are blown away. The rock fragments are greater than 64 mm in
size with no upward limit to their size.
Lava blocks
Lava blocks are large pieces of rock blown out of a volcano which have angular
shapes and are solid. Some lava blocks are pieces of the volcano vent or sides
of the volcano when it blows apart. The pieces can be as big as a small car.
Lava blocks are the largest pieces of pyroclastic material ejected during a
violent eruption.
Pumice
Pumice is light-colored igneous rock blown into the air in a semi-liquid state.
The rock cools so fast it does not have time to crystallize. Gas bubbles inside
the molten lava expands producing a rock that resembles a sponge.
Floating rocks
Pumice is often buoyant enough to float and has been known to float for
thousands of miles after a major eruption. It is often found on the shores of
volcanic islands thousands of miles from the eruption.
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Pyroclastic Flows
This eruption of Mt. Pinatubo caused
LOWER GLOBAL TEMPERATURES
19
Volcanoes
• Igneous Rock – formed when magma hardens
below the ground. Eventually, the process of
erosion wears down rock at the surface,
exposing features such as
– Batholiths
– Dikes
– Sills
20
Igneous Rock Features
• Batholiths – largest igneous rocks formed
when magma cools underground.
• Dike – magma that is squeezed into a
generally VERTICAL crack that cuts across rock
layers and hardens
• Sill – magma that is squeezed into a
HORIZONTAL crack between rock layers and
hardens
21
Volcanoes
• Volcanic Neck- the solid igneous core of a
volcano left behind when a volcano stops
erupting
• Caldera – large opening formed when a
volcano collapses
22
Caldera formation
23
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Hot Spots
• Areas of volcanic activity in middle of a plate
• Exact cause is unclear, possibly due to hot area of
magma under the lithosphere
• There are two equally valid hypotheses that might
explain hot spots:
– The plate could be moving over a stationary hot plume in
the mantle, or the hot area causing the volcanic activity
may be moving under a static, unmoving surface. At this
point in our explorations, we are unable to confirm one or
the other hypothesis--each is worthy of consideration.
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Volcanic Results
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Wk. 2 Day 3
Before: Question of the Day
What are pea-size to walnut-sized pieces of volcanic rock?
During: volcano in a cone Activity
After: Review
29
Wk. 2 Day 4
Before: Question of the Day
What are Hot Spots?
During: Review
Mini- Q
30
Wk. 2 Day 5
Before: Question of the Day
What is a caldera?
During: Review
Mini Test
31
Week 3
December 14-18
32
Wk. 3 Day 1
Volcano
Summative Assessment
33
Wk. 3 Day 2-5
Exam Review and Exams
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