VolcanoNotes
EOSC 114: Volcanoes Notes from Web Notes
Lesson 1: Why Do Volcanoes Have Different Characteristics?
A. Formation of Lava
Magma is formed by melting preexisting rock in Earth’s interior
For magma to rise through crust it must be:
(1)less dense than the crust
(2) runny enough to flow
(3) hot enough to stay liquid
Magma that cools to form solid rock = lava
B. Composition of Magma/Lava
Magma is composed of various proportions of:
Oxygen, Silicon, Aluminum, Iron, Calcium and Potassium
Mineral – naturally occurring element or compound that has an ordered internal structure, a characteristic chemical composition, crystal form and physical properties.
Most minerals from magma – silicate minerals from (SiO4)
Size of crystals that form – Dependent of how long magma takes to cool
Magma that cools slowly underground = intrusive rock
Magma that cools quickly (outer) = extrusive or fine-grained
C. Volcanic Products
1. Lava Flows
Relatively low in gas content, magma erupting effusively at Earths surface
Surface of lava flow may have ropy-texture called pahoehoes
Rubble-y flow top consisting of broken lava fragments is called a’a
2. Volcanic Glass - Magma erupts and cools so quickly that crystallization does not occur - Solidifies into a glass - Massive, Dark – Osideon - Bubbly, light – Pumice
3. Pyroclastic Materials - fragments of all sizes that are erupted explosively out of a volcano - Ash (<2mm) - Lapilli (2-64mm) - Blocks and Bombs (>64mm)
4. Gaseous Products - compounds bubble out of magma
D. Explosivity of Magma
1. Factors Affecting Explosivity
a. Gas Content – higher gas content have more explosive eruptions
2. Viscosity resistance to flow easy flowing magma (low viscosity) – gas bubbles dissipate – erupt effusively
High Gas Content + High Viscosity = Explosive Volcanic Eruptions
Viscosity Factors - Chemical Composition, the more SiO2 present, the higher the viscosity - temperature, the cooler, the more viscous
The Higher the M Value
Lesson 1: Why Do Volcanoes Have Different Characteristics?
A. Formation of Lava
Magma is formed by melting preexisting rock in Earth’s interior
For magma to rise through crust it must be:
(1)less dense than the crust
(2) runny enough to flow
(3) hot enough to stay liquid
Magma that cools to form solid rock = lava
B. Composition of Magma/Lava
Magma is composed of various proportions of:
Oxygen, Silicon, Aluminum, Iron, Calcium and Potassium
Mineral – naturally occurring element or compound that has an ordered internal structure, a characteristic chemical composition, crystal form and physical properties.
Most minerals from magma – silicate minerals from (SiO4)
Size of crystals that form – Dependent of how long magma takes to cool
Magma that cools slowly underground = intrusive rock
Magma that cools quickly (outer) = extrusive or fine-grained
C. Volcanic Products
1. Lava Flows
Relatively low in gas content, magma erupting effusively at Earths surface
Surface of lava flow may have ropy-texture called pahoehoes
Rubble-y flow top consisting of broken lava fragments is called a’a
2. Volcanic Glass - Magma erupts and cools so quickly that crystallization does not occur - Solidifies into a glass - Massive, Dark – Osideon - Bubbly, light – Pumice
3. Pyroclastic Materials - fragments of all sizes that are erupted explosively out of a volcano - Ash (<2mm) - Lapilli (2-64mm) - Blocks and Bombs (>64mm)
4. Gaseous Products - compounds bubble out of magma
D. Explosivity of Magma
1. Factors Affecting Explosivity
a. Gas Content – higher gas content have more explosive eruptions
2. Viscosity resistance to flow easy flowing magma (low viscosity) – gas bubbles dissipate – erupt effusively
High Gas Content + High Viscosity = Explosive Volcanic Eruptions
Viscosity Factors - Chemical Composition, the more SiO2 present, the higher the viscosity - temperature, the cooler, the more viscous
The Higher the M Value