Volcanoes

Question 1

Relation between Silica, Viscosity, thickness, and explosivity

Answer 1

Silica ∝ Viscosity ∝ Thickness ∝ Explosiveness of Volcano

Question 2

Types of Volcano based on magma characteristics

Answer 2

1. Shield Volcanoes
   - Low Viscosity
   - Non - Explosive (Exception: Reaction with H20 makes it explosive)
   - Examples: Hawaiian Volcanoes such as Mauna Loa and Mauna Kea
2. Stratovolcanoes
   - High viscosity and highly gaseous
   - Felsic Magma
   - Examples: Mount Stromboli (Light house of Mediterranean), Mount Vesuvius, Krakatoa, and Mount Fuji
3. Flood Basalt Volcanoes
   - Fissure Type
   - Examples: Siberian Traps, Deccan Traps, Snake Basin, Icelandic Shield, and Canadian Shield
4. Cinder Cones
   - Short eruptions
   - Releases only Pyroclastic

Question 3

Types of Volcanoes based on eruption

Answer 3

1. Active Volcanoes
   The volcanoes which erupt frequently

Examples:
Etna, Vesuvius, Barren Islands in the Andaman and Nicobar Islands, Anak Krakatoa, and Stromboli Volcano

2. Dormant Volcanoes
   Not erupted regularly, possibility of eruption in future

Examples:
Mt. Kilimanjaro (Tanzania)

3. Extinct Volcanoes
   Dormant volcanoes for 100s of years
   Before becoming extinct, the steam and other hot gases are exhaled which are known as Fumaroles / Solfataras

Question 4

Basaltic Lava
Occurrence: _________
Origin: _________
Composition: _________
Explosivity: _________
Flow Dynamics: _________
Volcanic LFs: _________

Answer 4

Occurrence: Along constructive/divergent boundaries with fissure type eruptions

Origin: Mantle with less Silica and hottest type of lava

Composition: Rich in Fe & Mg, Mafic

Explosivity: Low

Flow Dynamics: Flows to larger areas quietly

Volcanic LFs: Shield Volcanoes

Question 5

Types of basaltic lavas

Answer 5

1. Pahoehoe - Low Silica
2. Aa - High Silica

Question 6

Andesitic Lava
Occurrence: _________
Origin: _________
Composition: _________
Explosivity: _________
Flow Dynamics: _________
Volcanic LFs: _________

Answer 6

Occurrence: Along constructive/divergent boundaries where subduction occurs

Origin: Crust with more silica

Composition: Light colored and Low dense

Explosivity: High

Flow Dynamics: Slow flow

Volcanic LFs: Throws out many volcanic bombs (or) pyroclasts

Question 7

Which gases released in volcanic eruption?

Answer 7

H2o (g), CO2, SO2, H2S, HCl

Question 8

Pyroclastic Materials

Answer 8

Tephra: Loose material

Volcanic Ash (Diameter < 2mm)
Cinder/Lapilli (Diameter 2mm - 64mm)
Volcanic Blocks/Bombs (Diameter > 64mm)

Lahars/Volcanic Mudflows: Fast-flowing mixtures of water, volcanic ash, and other debris

Question 9

Intrusive Volcanic LFs

Answer 9

1. Batholiths: Large granitic rock bodies formed due to the solidification of hot magma inside the earth
2. Laccoliths: Large dome shaped plutons (intrusive bodies) connected to Batholiths
3. Lopolith: Saucer shaped plutons by horizontal flow of magma
4. Phacolith: Lens shaped plutons with Anti-cline and Syn-cline
5. Sills: Horizonal plutons (referred as sheets if thickness is less)
6. Dykes: Vertical plutons