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
