Presentation1.pptx volcano..............

Lesson Objectives
• Identify the different types of
volcanoes based on shape and
structure (e.g., shield, composite,
cinder cone, and lava dome);
• assess prior knowledge about types of
volcanoes;
• appreciate the diversity of volcanic
landforms and their role in shaping
Earth’s surface.

Source:
britanicca
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Have you ever heard of Mount
Mayon or Mount Pinatubo? What
comes to mind when you think of
volcanoes?

Volcanoes are not just fiery
mountains; they play an important
role in shaping Earth's surface,
creating new land, and even
influencing the climate.

Did you know that the Philippines is
part of the Pacific Ring of Fire, a
region known for its many volcanoes?

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What is a Volcano?

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A volcano is a landform that allows
magma, gases, and ash to escape
from beneath Earth's crust. When
magma reaches the surface, it is
called lava.

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The Four Types of
Volcanoes

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1.Shield Volcanoes
⚬ These are broad and dome-
shaped with gentle slopes,
resembling a warrior's shield
lying on the ground.
⚬ Formed by low-viscosity lava
that flows easily over long
distances.

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• Example:
⚬ Mauna Loa in Hawaii, the largest
volcano on Earth.
• Key Features:
⚬ Eruptions are usually calm and
effusive.
⚬ Build up layers of lava over time.

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2. Composite Volcanoes
(Stratovolcanoes)
• Description:
⚬ Tall, cone-shaped, and steep-
sided volcanoes formed by
alternating layers of lava and
ash.

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• Example:
⚬ Mount Mayon in the Philippines,
famous for its near-perfect cone.
• Key Features:
⚬ Known for violent, explosive
eruptions due to high gas
pressure.
⚬ Eject ash, lava, and volcanic
rocks during eruptions.

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3. Cinder Cone Volcanoes
⚬ Description:
￭ Small, steep-sided
volcanoes made of loose
volcanic fragments called
cinders.

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• Example:
⚬ Parícutin in Mexico, which grew
from a farmer's cornfield in
1943.
• Key Features:
⚬ Eruptions are short-lived and
mostly involve the ejection of
lava fragments.
⚬ These volcanoes are usually
smaller and less destructive.

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4. Lava Dome Volcanoes
• Description:
￭ Small, steep-sided domes
formed by slow, thick lava
that piles up near the
vent.

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• Example:
⚬ The lava dome at Mount St.
Helens in the United States.
• Key Features:
⚬ Lava is highly viscous and
doesn’t flow far.
⚬ Can build up pressure and cause
explosive eruptions.

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Volcanic activity can be very fascinating.
After an explosive eruption, a scenic
cone-shaped structure may be
produced or changes on its slope can
be observed.
The emissions of a volcano provide us
with clues on what materials are found
inside
the Earth. Some eruptions are very
explosive, while many others are not.

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What determines the nature of
eruption? There are primary factors
affecting the
volcanoes’ eruptive style, namely: the
magma’s temperature, its chemical
composition, and the amount of
dissolved gases it contains. These
factors can affect
the magma’s viscosity in different ways.

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Viscosity is the property of the
material’s
resistance to flow. It is also described as
the liquid’s thickness and stickiness. The
more viscous and thicker the material
is, the greater is its resistance to flow.
For instance, syrup is more viscous than
water.

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Let us discuss how each factor affects the
viscosity of magma. First, let us look
into how temperature of magma affects its
viscosity. The viscosity of magma
decreases with temperature. The higher the
temperature of magma is, the lower is its
viscosity. As lava flows, it cools and begins
to harden, its ability to flow decreases and
eventually it stops.

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Next, let us look at how the composition of
magma affects its viscosity. Magmas
with high silica content are more viscous
than those with low silica content. The
magma that contains less silica is relatively
fluid and travels far before Solidifying.

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Lastly, the amount of gases
contained in the magma affects its
viscosity. Other factors being equal,
gas (mainly water vapor) dissolved in
magma tends to increase its ability
to flow. Therefore, in near-surface
environments, the loss of gases
makes magma more viscous,
forming a dome or a columnar

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Why Are Volcanoes
Different?

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The shape and structure of a volcano
depend on three main factors:
1.Type of Lava:
⚬ Runny lava (low viscosity) creates
wide, flat volcanoes like shield
volcanoes.
⚬ Thick lava (high viscosity) forms
steep-sided volcanoes like lava
domes.

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2. Eruption Style:
⚬ Quiet eruptions result in gentle
slopes.
⚬ Explosive eruptions lead to steep-
sided volcanoes.

3. Eruption Frequency:
⚬ Frequent eruptions create larger
and more developed volcanoes.

Presentation1.pptx volcano..............

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