Test 2: Volcanism Flashcards
What are Pyroclastic Materials?
Magma fragments that are explosively ejected by volcanoes, most are solid.
Which Volcano?
Rhyolitic lava flows-most viscous
Very Explosive
Lava Domes
Which Volcano?
Layers of lava flows and pyroclastic debris Steep Cone Shaped Intermediate compositions-andesite Explosive “Ring of Fire”`
Composite Volcanoes
Which Volcano?
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Gentle slopes and rounded shapes
Basaltic lava flows
Non-Explosive
Hawaiian Volcanoes
Komotilite
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Shield Volcanoes
Which Volcano?
Pyroclastic materials
Steep cones
Rarely exceed 400 m high
Cinder Cones
True or False?
The shape and eruptive style of volcanoes are related to the chemistry and viscosity of their magmas.
True
The shape and eruptive style of volcanoes are related to the chemistry and viscosity of their magmas.
Rhyolitic lava flows:
Creates Lava Dome
Lava Dome holds in gases
Flows have broken and blocky surfaces
Andesitic lava flows:
Flows slowly
Cone shape
Made up of Pyroclastic and lava
Basaltic lava flows: Flows fast (30-50km/hr)
Flows fast (30-50km/hr)
Komatiite lava flows:
Has not erupted in about 2.5 billion years
Silica Content
Rhyolite:
High silica content (70-75%)
High Viscosity
Silica Content
Andesite:
Intermediate silica content (60-65%)
Intermediate Viscosity
Silica Content
Basalt:
Low silica content (50-55%)
Low Viscosity
Silica Content
Komatiite:
Limited Silica (Below 40%) Very Low Viscosity
Fine: (No big crystals) (It’s lave) (Came to the surface) (Cooled first, causing crystals not being able to grow)
Extrusive Igneous Rock
Basalt, Andesite, Rhyolite, Komatiite
Course: (Big Crystals) (Didn’t come to the surface)
Intrusive Igneous Rock
Granite, Diorite, Gabbro, Peridotite
What does Viscosity affect?
Viscosity affects the flow of lava and therefore the shape of the resulting volcano
In explosive eruptions, _____is ejected
In explosive eruptions, tephra is ejected
What is an accumulation of tephra called?
An accumulation of tephra is a Pyroclastic deposit
What is the term for anything that explodes out of the volcano?
Pyroclastic is anything that explodes out of the volcano
Molten rock material below the earth’s surface
Magma
Magma turns into a liquid when the surface is reached, creating lava
Lava
The viscosity of Magma is controlled by ______?
The viscosity of Magma is controlled by Silica Content
More Silica causes a ______explosion
More Silica causes a bigger explosion (Builds up pressure)
Less Silica makes for a ______explosion
Less Silica makes for a smaller explosion
How do we have magma?
Decompression (Weight onto of it, prevents it from being liquid)
Addition of volatiles (Adding water breaks chemical bonds, creating fluid)
Addition of heat (When magma comes up it warms adjacent material, turning it into liquid)
The tectonic setting determines the type of volcano
Mid-ocean ridges, subduction zones, hot spots
Mixing of Basalt and Granite create andesite which makes cone volcanoes
Subduction Zones
The tectonic setting determines the type of volcano
Mid-ocean ridges, subduction zones, hot spots
One section is moving one way and another section is moving a different way, the magma pushes through the weak spot creating lava.
Mid-Ocean Ridges
The tectonic setting determines the type of volcano
Mid-ocean ridges, subduction zones, hot spots
Magma is stationary, but the plates are moving so there is a build-up of magma pressure which creates small islands.
Hot Spots
Where does the Ring of Fire surround?
The Ring of Fire surrounds the Pacific Ocean. (Surrounds Pacific Ocean) (Subduction zones)
How many of all active volcanoes on land are located along the Ring of Fire which surrounds the Pacific Ocean?
2/3
Popular Volcanoes
Still active (Pompeii)
Mount Vesuvius, Italy