Volcanoes Flashcards
Weak spots in the earth’s crust through which molten material (magma) moves onto the surface
Volcanoes
Layer within earth’s mantle where temperature and pressure are high enough to melt rocks
Asthenosphere
Volcanoes are commonly formed along…
Plate Boundaries
Area over a mantle plume or under the crust where magma is hotter than surrounding magma
Hot Spots
How are volcanoes formed through hot spots?
Magma rises up through crust and forms a volcano, when the plate moves, the volcano is carried away from the hotspot becoming inactive, and new volcanoes can form
It is a well-known example of islands formed by a volcanic chain coming from hot spots
Hawaiian Islands
This active volcano is currently located above the Hawaiian Islands’ hot spot
Mount Kilauea
Molten material INSIDE a volcano
Magma
Molten material after reaching the earth’s surface
Lava
It is where magma is collected inside the earth
Magma Chamber
Bowl-shaped basin at the top of a volcano
Crater
Main passageway for magma to escape
Main Vent
Smaller outlets for magma to escape
Secondary Vents
Classifications of Volcanoes according to activity
- Active
- Potentially Active (dormant)
- Inactive (Extinct)
A volcano expected to erupt or is already erupting
Active
A volcano that isn’t erupting and isn’t predicted to erupt in the near future
Potentially Active (Dormant)
A volcano not expected to ever have another eruption
Inactive (Extinct)
How long ago does a volcano’s last eruption have to be before being considered extinct?
10,000 years
Types of Volcanic Eruption
Effusive and Explosive
Type of eruption wherein lava flows out of the crater and drifts into the volcano’s base without too much volcanic materials in the air
Effusive Eruption
Type of eruption wherein magma and other pyroclastic materials are expelled into the air
Explosive Eruption
Types of Lava Flow
Aa and Pahoehoe (pronounced pahoyhoy)
Blocky, rough lava flow
Aa Flow
Fluid lava flow, appearing in smooth thin broad sheets
Pahoehoe Flow
Gases dissolved in magma come out in the form of…
Bubbles !! 🫧
Most important dissolved gases
Water vapor, carbon dioxide, sulfur
Describe relationship between dissolved gases and explosiveness
Higher dissolved gases, more explosive
Ability of a liquid to resist flow
Viscosity
Determines ability of lava to flow
Temperature of Magma
Describe relationship between magma’s temperature and lava flow
Higher temperature, lesser viscosity (lava flows easily)
Magma Compositions
- Basaltic / Mafic
- Rhyolitic / Felsic
- Andesitic
Thin and fluid due to low silica content, can travel a distance of up to 150 km
Basaltic / Mafic
70% silica, thick and stiff
Rhyolitic / Felsic
Intermediate between basaltic and rhyolitic
Andesitic
Classification of Volcano according to structure
- Shield Volcanoes
- Cinder Cone Volcanoes
- Composite Volcanoes
Broad dome structure that covers large areas
Shield Volcano
Well-known examples of Shield Volcano
- Mauna Loa in Hawaii
- Olympus Mons in Mars
Steep slopes and relatively small (about 300m high)
Cinder Cone Volcanoes
Cone shaped volcanoes built from lava fragments called cinders
Cinder Cone Volcano
Well-known example of Cinder Cone Volcano
Taal Volcano in Batangas
Has a large and nearly symmetrical structure
Composite Volcanoes
