Types of Eruptions: Explosive and Nonexplosive
-
Upload
shannon-elliott -
Category
Documents
-
view
217 -
download
0
description
Transcript of Types of Eruptions: Explosive and Nonexplosive
Types of Eruptions: Explosive and Nonexplosive
Geology 12 Ms. Bowie Types of Lava There are 4 main types of lava:
Aa (pronounced Ah-Ah)
Pahoehoe (pronounced pa-hoy-hoy) Pillow Blocky Volcano Shapes &
Eruption Types
The shape of volcanoes and the violence of the eruptions depend on
the same rather thing: the physical properties of erupting lavas.
Volcano Shapes & Eruption Types
The two most important properties of lava are: its viscosity, the
amount of gases dissolved in the liquid rock. Lava Viscosity
Viscosity is the thickness or runniness of the fluid The
explosivity of lava depends on several factors: Composition -
especially the amount of silica (SiO2) in the lava. Amount of gases
dissolved in the lava (H2O & CO2) Pressure generated Low
Viscosity Little Gas
Lava with a small amount of silica and little dissolved gases tend
to be: Runny Mildly bubbly Under Low pressure This results in lava
that flows fairly gently and smoothly out of the volcano. Low
Viscosity Little Gas
This is called Pahoehoe Pahoehoe (pa-hoy-hoy) lava flows develop
surface crusts that form thick plates with ropy and/or gently
undulating surfaces. Pillow Lava Lower viscosity lava that erupts
under water forms rounded mounds that look like pillows. Moderate
Viscosity Lava
Lava with a moderate amount of silica and little dissolved gases
tend to be: Lumpy Moderately bubbly Under Moderate pressure This
results in lava that flows less easilyand somewhat bumpy out of the
volcano. Aa-Lava Aa (Ah-Ah) lava flows have a very rough, rubbly
surface because of their high eruption rates. Pieces of the rocky
surface are broken, rolled and tumbled along as the lava flow
moves. When finally cooled to a solid, aa lava flows look like a
jagged heap of loose rock. Low Viscosity High Gas
Lava with a little silica but lots of dissolved gases tend to be:
Frothy Tossing into the air lava, cinders & lava bombs This
results in spectacular lava fountains that toss materials
predictably and impressively into the air above the vent. High
Viscosity High Gas
Lava with a large amounts of silica and dissolved gases tend to be:
Thick & Gooey Pockets of trapped gas Under High pressure This
results in lots of gas trapped under thick lava. The pressure
builds until it blows the entire top of the volcano. Pyroclastic
Material from EXPLOSIVE ERUPTIONS
4 types of pyroclastic material: a. Volcanic blocks b. Volcanic
bombs c. Lapilli d. Volcanic Ash Volcanic Bombs Volcanic bombs are
large pieces of magma that harden in the air as the erupt out of a
volcano. They can form in a variety of sizes and shapes. Lapilli
Lapilli means little stones in Italian.
They are tiny pieces of magma that harden before they hit the
ground. Volcanic Ash Volcanic ash forms when gases in stiff magma
expand rapidly. The walls of the gas bubbles explode into tiny
glasslike slivers. Ash makes up most of a pyroclastic eruption.
High Viscosity Low Gas
Blocky Lava Cool stiff lava that does not travel far from the
erupting vent. It cools and form sharp edged chunks. Review List
the 4 types of lava.
This type of lava is very rough with jagged edges. This type of
lava forms from underwater eruptions, looks like rounded lumps.
This type of lava has a smooth surface and rounded edges. This type
of lava forms sharp edged chunks. List the four types of
pyroclastic material. These are large blobs of magma that have
cooled and hardened as they flew through the air. These are tiny
pieces of magma that have hardened in the air. These are solid rock
fragments and usually consist of pieces of the old volcano. This is
formed from when gases in stiff magma expand and explode into
slivers. Answers Aa, pahoehoe, pillow, blocky Aa Pillow Pahoehoe
Blocky
Blocks, bombs, lapilli, ash Bombs Lapilli Blocks Ash