All About Volcanoes

Lesson 8: Volcanoes

2nd Quarter | Earth Science 7

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Video: Volcanoes 101

Open Ended

Write everything you know about volcanoes.

Open Ended

What would you like to learn about volcanoes today?

Lesson Objective:

Explain how volcanoes change the Earth's Surface

What is a Volcano?

• A vent in the Earth's crust where molten rock flows

• Magma= underground liquid/ molten rock

• Lava = above-ground liquid/ molten rock

Multiple Choice

Molten rock above the ground is called

• Magma

• Lava

video: parts of a volcano

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Multiple Choice

Which of the following is the main vent of a volcano?

• Crater

• Central vent

• Parasitic cone

• Fumarole

Multiple Choice

1. 
   Where does magma accumulate before it erupts through the volcano?

• Magma Chamber

• Crater

• Vent

• Lava dome

Multiple Choice

1. 
   Which feature is formed by the accumulation of hardened lava around the vent?

• Crater

• Cone

• Vent

• Lava dome

How do Volcanoes form?

• Movement of tectonic plates causes eruptions and volcanoes

• Shape the Earth's surface

• Make mountains, new crust, destroy forests / land

Convergent Plate Boundary Volcanoes

• The denser plate subducts and becomes molten rock/ magma

• The magma rises through the cracks in the crust

• a volcano is formed

Multiple Choice

Which type of crust is the densest and will subduct in a convergent boundary?

• Continental Crust

• Oceanic

Divergent Plate Boundary Volcanoes

• When plates separate, magma flows up

• Happens the most at Mid Ocean Ridges

HOT SPOTS

• Not all volcanoes occur at plate boundaries

• Tectonic plates move over magma plumes

• Plumes are convective currents of magma

• Hawaii is an example of this

Multiple Choice

Where do volcanoes NOT occur?

• Convergent plate boundaries

• Divergent plate boundaries

• Transform plate boundaries

• Hot Spots

The Pacific Ring Of Fire

• An area in the Pacific that has a lot of volcanic and seismic activity

• The Philippines is located in the Pacific Ring of Fire

Multiple Choice

The Philippines is not part of the Pacific Ring of fire.

• True

• False

Volcanoes in the Philippines

• There are around 300 volcanoes in the Philippines

• 24 of these are active.

Volcanic Features/Shapes

• Shield: large, gentle slopes, basaltic lava

  Example: Mauna Loa in Hawaii

• Composite: large and steep-sided, explosive eruptions

  Example: Mayon Volcano

• Cinder Cones: small steep sided, erupt gas rich basaltic lava

  Example: Taal Volcano

​Types of Volcanoes

Active volcanoes have a recent history of eruptions within the past 600 years; they are likely to erupt again.

Inactive volcanoes have not erupted in a long time but are expected to erupt again in the future.

Extinct volcanoes those which have not erupted in human history. 

Volcanic Eruptions

• Can be a Gentle lava flow (think Hawaii)

• Can be Explosive (Mount St. Helens,1980)

• Depends on the chemistry of the magma

Magma Chemistry

• Silica affects viscosity (how it flows)

• Low silica means it flows easier, fluid lava and makes basaltic rock, found at Mid ocean ridges and ocean hot spots (Hawaii)

• High viscosity flows like sticky toothpaste, makes rocks like rhyolite and andesite, found at subduction zones and continental hot spots (Mount. St. Helens)

Multiple Choice

What kind of magma SILICA content causes big, explosive volcanic eruptions?

• Low

• High

Magma Chemistry (Dissolved gases)

• Contributes to how explosive an eruption can be

• Water Vapor, Carbon Dioxide, Sulfur Dioxide

• As magma approaches the surface of the Earth, less pressure holding the gas in the magma

• Eruptions caused by the gas bubbles building and escaping.

• Explosions happen bc gas doesn't easily escape from high silica magma

Multiple Select

What 2 things determine how explosive a volcanic eruption is?

• Silica Content

• Sulfur Content

• Dissolved Gases

• Plate boundary

A pyroclastic flow is a dense, fast-moving flow of solidified lava pieces, volcanic ash, and hot gases.

It is extremely dangerous to any living thing in its path.

Pyroclastic Flow

Fumaroles are openings in the earth's surface that emit steam and volcanic gases, such as sulfur dioxide and carbon dioxide.

Fumarole

Pahoehoe is lava that in solidified form is characterized by a smooth, billowy, or ropy surface.

Pahoehoe

Multiple Select

What 2 things determine how explosive a volcanic eruption is?

• Silica Content

• Sulfur Content

• Dissolved Gases

• Plate boundary

Effects of Volcanic eruptions

• Lava Flows: rarely deadly, but damaging

• Ash falls: particles of rock/glass, dangerous, heavy, affects air quality and climate

• Mudflows: heat can melt snow and ice on the summit mix with ash and cause a flowing river of mud called lahars

• Pyroclastic flows: fast moving avalanches of gas, ash and rock

Poll

Which of the volcanic effects do you think is most dangerous?

• Ash Fall

• Mudflow

• Pyroclastic flow

• Lava Flow

Open Ended

What do you think is the difference between Lava and pyroclastic flow?

Multiple Choice

Which is the best definition of Fumarole?

• It is rich in Oxygen

• It is a type of lava

• It is rich in Sulfur dioxide

• It is a type of magma

Multiple Choice

Which is NOT a characteristic of Pahoehoe lava?

• It is a rough, rocky lava

• It is a sticky lava

• It is solidified and smooth

• It is ropy and billowy

Open Ended

What questions do you have in mind right now?