Chapter 9: Volcanoes and Igneous Activity Flashcards
Factors that determine the violence of an eruption.
1) composition of magma
2) temperature of magma
3) dissolved gases in magma
Viscosity
is a measure of a material’s resistance to flow
EX: the flow of honey when cold and heated up.
The factors affecting the viscosity of magma
1) temperature
2) composition
3) dissolved gases
two components to the composition of viscosity
high silica - high viscosity
low silica- low viscosity
The process which lava flows
moves through the asthenosphere and then through the continental crust to the surface aka the lithosphere
Basaltic lava
mafic lavas that are more fluid thank felsic lavas
Types of lava
Pahoehoe lava (resembles braids in rope) Aa Lava (rough, jagged blocks)
Volcanic gases
gases make up 1-5% of magma by weight
mainly water vapor and carbon dioxide
Examples of Pyroclastic Materials
Scoria
Pumice
Volcanic ash, volcanic bombs, lapilli, and volcanic blocks
Volcanoes general features
Volcanic pipe vent lava tube crater caldera
volcanic pipe
carries gas-rich magma to the surface
vent
the surface opening (connected to the magma chamber via a pipe)
lava tube
tunnel in a hardened lava that acts as a conduit for molten lava to flow from vent
Crater
steep-wall depression at the summit
Caldera
a summit depression greater than 1 km diameter
What is the difference between a crater and caldera?
A crater is a steep walled depression at the summit of the volcano
A caldera is a depression greater than 1 km in diameter
Different types of volcanoes
Shield volcano
Cinder cone
Composite
Shield Volcano
Slightly dome shaped
Primarily made of balsamic (fluid) lava
Generally the largest volcano
Most begin as seamounts on the bottom
of the ocean floor
Resembles a broad shield in profileCinder Cone Volcano
Volcanoes built from ejected lava fragments
Has a steep slope angle
Small in size, compared to shield or composite
Frequently occur in groups
Composite Volcano
Adjacent to Pacific Ocean aka “Ring of Fire”
Large, but not the biggest
produces the most violent activity
Nudee Ardente
“burning cloud”
fiery pyroclastic flow made of hot glasses infused with ash
Can produce lahar
Basalt
dark, fine-grained, igneous rock; makes up the majority of the ocean floor
Volcanic necks
are the resistant vents left standing after erosion has removed the volcanic cone
An underground igneous body is called what?
pluton
Types of intrusive Igneous Features
Dike - tubular pluton that moves at an angle
Sill- tubular pluton that is horizontal
(buried lava flow)
Laccolith - lens shaped (blister) magma mass
Batholith - largest intrusive body of all plutons
(forms the cores of mountains)
Examples of Igneous rocks
Granite
Pumice
Basalt
Examples of Sedimentary rocks
Sandstone
Brecca
Limestone
Examples of Metamorphic rocks
Gnesis
Marble
Schist
