Magmatism Flashcards
Endogenic Processes
- Magma Formation and Volcanism
- Diastrophism/Deformation
- Earthquake
- Metamorphism
Factors in Magma Formation
- temperature
- pressure
- addition of volatiles
molten rocks found beneath the earth’s surface
* temperature ranges from 800-1400 C
* possess the ability to flow due to high temperature
* commonly forms between the lower crust and the upper mantle
* less dense than surrounding rocks; therefore, capable of rising to the surface
* is called lava when it reached the surface
composed of abundant
elements
* most common component
is silica (about 45-75% by mass)
* contains dissolved gases
like CO2 and water vapor
(0.2-3%)
magma
flow of magma
mantle plume - hotspot - magma chambers
an area under the rocky outer layer of Earth, called the crust, where magma is hotter than surrounding magma. The heat from this extra hot magma causes melting and thinning of the rocky crust, which leads to widespread volcanic activity on Earth’s surface above it
mantle plume
- fed by a region deep within the Earth’s mantle from which heat rises through the process of convection. This heat facilitates the melting of rock at the base of the lithosphere, where the brittle, upper portion of the mantle meets Earth’s crust. The melted rock, known as magma, often pushes through cracks in the crust to form volcanoes.
occurs due to abnormally hot centres in the mantle known as mantle plumes.
volcanic hotspots
The location beneath the vent of a volcano where molten rock (magma) is stored prior to eruption. Also known as a magma storage zone or magma reservoir.
magma chamber
a fluid’s resistance to flow
- the state of being thick, sticky, and semifluid in consistency, due to internal friction.
- opposite of fluidity
viscosity
what affects the magma’s viscosity
silica content and temperature
More Silica/Lower Temperature
more viscous
Less Silica/Higher Temperature
less viscous (more fluid)
Factors Affecting Magma Formation
partial melting & fractionation
occurs when only a portion of a solid is melted. For mixed substances, such as a rock containing several different minerals or a mineral that displays solid solution, this melt can be different from the bulk composition of the solid.
(Rocks are composed of different minerals with different melting point, When the rocks begin to melt, only certain minerals are melted.)
partial melting
A eutectic mixture is a homogeneous mixture of substances that melts or solidifies at a single temperature that is lower than the melting point of any of the constituents. What is the term for its temperature?
Eutectic Temperature
During melting, magma that
formed first tends to be richer
in silica.
* Some minerals, usually
metals, can already
crystallize/remains solid
despite the high temperature.
* This high density rocks settle
at the bottom while less
dense magma will rise.
What is this called
Fractional Crystallization/Fractionation
Types of Magma Formation
heat transfer melting, decompression melting, flux melting
Types of Magma Formation
heat transfer melting, decompression melting, flux melting
The melting of surrounding rocks
due to the rising magma.
* Magma from the asthenosphere (upper mantle) melts the rocks in the lower crust.
* This occurs in hotspots, rift valleys, ocean ridges, and subduction zones or anything with the presence of magma
- through conduction
heat transfer melting
The temperature stays the same but the pressure decreases.
* It usually occurs in rift valleys, oceanic ridges, and volcanic hotspots/divergent plate boundaries
decompression melting
When water or volatile gases are
added, they will react with rocks
and will weaken or break their
bonds and cause them to change
from solid to liquid.
* This usually occurs in subduction
zones.
flux melting
What happens after magma is formed
Crystallization and Volcanic Eruption
describes the temperature at which minerals crystallize when cooled, or melt when heated.
- The sequence of mineral crystallization
- partial melting and fractionation
Bowen’s Reaction Series.
a Bowen’s reaction series branch where it starts with olivine, then pyroxene, amphibole, and biotite.
- reaction series - each mineral in the series is replaced by the next one as the molten cools.
- At a certain temperature, magma might produce olivine, but if that same magma was allowed to cool further, the olivine would “react” with the residual magma, and change to the next mineral on the series (in this case pyroxene). Continue cooling and the pyroxene would convert to amphibole, and then to biotite.
discontinuous series
this Bowen’s reaction series branch describes the evolution of the plagioclase feldspars as they evolve from being calcium-rich to more sodium-rich.
continuous branch
as the temperature drops, in Bowen’s reaction series, the branches merge and we obtain the minerals common to the felsic rocks - __________________________
orthoclase/potassium/alkaline feldspar, muscovite mica, and quartz (the banana slug of the mineral world)
Occurs when lava is ejected to the surface through an opening in the earth’s crust.
- can be explosive or effusive
volcanic eruption
non-explosive or quiet Eruption
* dominated by the flow of lava and the formation of fountains
and lakes
- Less Silica/Higher Temperature → Less Viscous
effusive eruption
violent or Plinian eruption
* ejects ash and larger
fragments of broken up
pyroclastic materials,
forming ash clouds that
eventually, collapse and
cover the slope of the
volcano
- More Silica/Lower Temperature → More Viscous
- Addition of volatiles such as water vapor and gases commonly
results to an explosive eruption
explosive eruption
TYPE OF ERUPTION BASED ON MAGMA-WATER INTERACTION
magmatic eruption, phreatic eruption, phreatomagmatic eruption
magma-driven eruption
(I Hate Some Very Popular People)
magmatic eruption (icelandic, hawaiian, strombolian, Vulcanian, pelean, plinian)
- characterized by effusions of molten basaltic lava that flow from long, parallel fissures. Such outpourings often build lava plateaus.
icelandic
- similar to the Icelandic variety. In this case, however, fluid lava flows from a volcano’s summit and radial fissures to form shield volcanoes, which are quite large and have gentle slopes.
hawaiian
- involve moderate bursts of expanding gases that eject clots of incandescent lava in cyclical or nearly continuous small eruptions. Because of such small frequent outbursts, Stromboli volcano, located on Stromboli Island off the northeast coast of Italy, has been called the “lighthouse of the Mediterranean.”
strombolian
- named for Vulcano Island near Stromboli, generally involves moderate explosions of gas laden with volcanic ash. This mixture forms dark, turbulent eruption clouds that rapidly ascend and expand in convoluted shapes.
vulcanian
is associated with explosive outbursts that generate pyroclastic flows, dense mixtures of hot volcanic fragments and gas that roll down slopes at high speed
pelean
an intensely violent kind of volcanic eruption
- The uprushing gases and volcanic fragments resemble a gigantic rocket blast directed vertically upward.
- clouds can rise into the stratosphere and are sometimes continuously produced for several hours.
- Lightning strikes caused by a buildup of static electricity are common close toits ash clouds, adding one more element of terror to the eruption.
plinian
KINDS OF VOLCANO ACCORDING TO SHAPE AND COMPOSITION
cinder cone, shield, composite
- has a wide base with gently
sloping sides
-made up purely of solidified
lava
-formed from an effusive eruption
Examples: Mauna Kea and
Kilauea Volcano in Hawaii,
Olympus Mons in Mars
shield cone volcano
composed of alternating layers
of lava and cinders
- formed when volcanic
eruptions vary between quiet
and violent and explosive.
Examples: Mt. Fuji in Japan, Mt.
Vesuvius and Mt. Stromboli in
Italy and Mt. Mayon in the
Philippines
composite volcano
-made up of loose fragments called cinders (pyroclasts and tephra)
-it has a narrow base and a steep
slope
-it is formed from explosive eruption.
Examples: Sunset Crater in Arizona,
Mt. Pelee’ in the West Indies
cinder cone volcano
KINDS OF VOLCANO ACCORDING TO ACTIVITY
active, potentially active, inactive/dormant, extinct
They erupted within the last 600 years based on history documented by man or if it
has erupted within the last 10,000 years based on the analyses of volcanic rock deposits.
(e.g. Mt. Mayon)
active
These are young-looking, or newly formed volcanoes but have no records of eruption whether based on historical or analytical data. (e.g Mt. Apo)
potentially active
These volcanoes have no
record of eruption and their physical forms were changed by erosion and weathering such as the formation of deep and long water channels. Although, they may still show signs of the presence of magma within by emission of gases and presence of hot springs. (e.g. Mt. Makiling)
- old
- inactive/dormant
This type of volcano is considered unlikely to erupt again because they do not have magma supply anymore. (e.g. Mt. Guinsiliban)
extinct
