EARTHSC 1121 Lecture Notes - Lecture 9: Mantle Plume, Magma Chamber, Continental Crust

39 views5 pages
Volcanic Eruptions & Formation of Igneous Rocks
KEY
1. Vocabulary
Volcanic Eruptions
Volcano: an erupting vent through which molten rock surfaces, a mountain built
from magnetic eruptions
Volcanoes are a clear result of tectonic activity
Volcanoes pose a number of hazards to humans
o Why do we live by them? (Seattle, Mexico City, Naples)
It is really easy to grow crops because the soil is nutrient rich
People like to ski on the side of volcanoes and they are pretty
Example: Mt. Vesuvius (79 C.E) destroyed Pompeii but a record of Roman life was
preserved
Unpredictable, dangerous
o Build large mountains
o Blow mountains to bits
Eruptions can…
o Provide highly productive solid to feed a civilization
o Can extinguish a civilization in a matter of minutes
Eruptions affect climate
Tectonic Settings
Plate motion is a dominant control on volcanism
Volcanic types are linked to tectonic settings…
o Hot spots: where mantle plumes cut the lithosphere
Oceanic hot spot (Hawaii)
Continental hot spots and flood basalts (Yellow Stone)
o MOR spreading axes
o Convergent boundaries subduction zones
o Continental Rifts incipient ocean basins
Setting is a dominant control of…
o Magma source
o Volcanic type
Shape
Rock compositions
o Volcanic hazard
Composition
Eruptive style
Eruptive frequency
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 5 pages and 3 million more documents.

Already have an account? Log in
Magma Formation
Magma: molten rock
Why does magma form?
o Earth is hot inside. Why?
Planetesimals and meteorite formation
Gravitational compression
Differentiation
Radioactive mineral decay **
Primordial heat **
Partial melting in crust/upper mantle
Melting is from
o Pressure release (I)
o Volatile addition (II)
o Heat transfer (III)
Magma Formation (I)
Geothermal gradient Earth is hot inside
o Crustal temperature (T) increases 25 C / km with depth
o At the base of lithosphere T ~1,280 C
Geothermal gradient varies from place to place
Pressure Release
o Base of the crust is not quite hot enough to melt mantle rock
o Due to high pressure, the rock does not melt
o A drop in pressure initiates “decompressional melting”
Solidus: the lowest temperature at which a rock begins to melt
Liquidus: the highest temperature at which any part of the rock remains solid
MOR Eruptions
Magma generated by pressure release: Magma Formation (I)
Most lava erupts along the MOR
MOR-produced oceanic crust covers 70% of the Earth
Basalt (mafic) erupted from fissures quenches as pillows
Pillow mounds are pulled apart with plate motions
Hot Spot Eruptions Magma Formation (I)
Oceanic hot spot: plume under an oceanic plate
o Basalt erupts at the seafloor and forms a growing mound
o A volcano builds above sea level to form an island
o Then basalt will not quench and can flow long distances
o Lava builds upwards and outward and the island grows
o Submarine slumps remove large masses of the volcano
** Iceland is a hot spot beneath the MOR
find more resources at oneclass.com
find more resources at oneclass.com
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 5 pages and 3 million more documents.

Already have an account? Log in

Document Summary

Magma formation: magma: molten rock, why does magma form, earth is hot inside. Why: planetesimals and meteorite formation, gravitational compression, differentiation, radioactive mineral decay *, primordial heat *, partial melting in crust/upper mantle, melting is from, pressure release (i, volatile addition (ii, heat transfer (iii) Solidus: the lowest temperature at which a rock begins to melt. Liquidus: the highest temperature at which any part of the rock remains solid. ** iceland is a hot spot beneath the mor. Addition of volatiles (ii: volatiles cause rocks to melt at much lower temperature, water (like salt is to ice lowers the melting temp, carbon dioxide, adding volatiles to hot, dry rocks initiates melting, important subduction process. Magma formation (iii: heat transfer, rising magma carries mantle heat, this raises t in crustal rock, crustal rock melts at lower t. Continental hot spot eruptions: continental hot spots, yellowstone eruption 640 ka created a 100 km caldera, 1000 times more powerful than mt.

Get access

Grade+20% OFF
$8 USD/m$10 USD/m
Billed $96 USD annually
Grade+
Homework Help
Study Guides
Textbook Solutions
Class Notes
Textbook Notes
Booster Class
40 Verified Answers
Class+
$8 USD/m
Billed $96 USD annually
Class+
Homework Help
Study Guides
Textbook Solutions
Class Notes
Textbook Notes
Booster Class
30 Verified Answers