Lec 5: Igneous Rocks and Volcanic Activity Flashcards
Lecture’s goals:
IGNEOUS ROCKS
1_ List and describe the ways that igneous rocks form and how this affects rock texture
2_ Describe how magma generation is related to plate tectonics
3_ Compare and contrast igneous rocks of mafic and felsic composition
4_ Predict the mineral composition of igneous rocks based on Bowen’s reaction series
VOLCANIC ACTIVITY
5_ Use the composition of magma and shape/type of a volcano to predict if it will erupt explosively
6_ Compare and contrast 2 of the most important types of volcanoes
7_ Describe how volcano type is related to plate tectonics
8_ List and describe a selection of volcanic hazards
Lecture’s goals:
IGNEOUS ROCKS
1_ List and describe the ways that igneous rocks form and how this affects rock texture
2_ Describe how magma generation is related to plate tectonics
3_ Compare and contrast igneous rocks of mafic and felsic composition
4_ Predict the mineral composition of igneous rocks based on Bowen’s reaction series
VOLCANIC ACTIVITY
5_ Use the composition of magma and shape/type of a volcano to predict if it will erupt explosively
6_ Compare and contrast 2 of the most important types of volcanoes
7_ Describe how volcano type is related to plate tectonics
8_ List and describe a selection of volcanic hazards
Lecture’s goals:
IGNEOUS ROCKS
1_ List and describe the ways that igneous rocks form and how this affects rock texture
1st way that igneous rock forms is from the cooling and crystallization of molten rock (magma/lava)
2 words to remember:
_ intrusive = from underground
_ extrusive = form above ground
intrusive:
_ cooled relatively slowly
_ large crystals
_ phaneritic texture (coarse)
Extrusive:
_ cooled relatively quickly
_ small crystal
_ aphanitic texture (fine)
2 stages cooling: larger crystals embedded in a matrix of smaller crystals = mixed (porphyritic)
Lecture’s goals:
IGNEOUS ROCKS
2_ Describe how magma generation is related to plate tectonics
. The majority of red color is not magma, only a small amount that fairly close to the surface (asthenosphere)
Rocks melt by adding heat, reduction of pressure, and addition of volatiles
Magma generation relates to plate tectonics:
_ convergent plate boundaries: volatiles as oceanic plates subduct under the continental plate. This creates felsic magma
_ divergent plate boundaries (oceanic spreading ridge): mafic magma produced
_ others: accounts for magmatic activity not at a plate boundaries
Lecture’s goals:
IGNEOUS ROCKS
3_ Compare and contrast igneous rocks of mafic and felsic composition
Felsic: feldspar and silica
Mafic: magnesium and iron
Example:
Felsic-intrusive(coarse): granite
Mafic-extrusive(fine): rhyolite
Lecture’s goals:
IGNEOUS ROCKS
4_ Predict the mineral composition of igneous rocks based on Bowen’s reaction series
High temperature - mafic: olivine
Intermediate: pyroxene, then amphibole
Lower temperature - felsic: biotite
Lecture’s goals:
VOLCANIC ACTIVITY
5_ Use the composition of magma and shape/type of a volcano to predict if it will erupt explosively
Explosiveness = high viscosity (slowly move liquid, sticky) + gas content magma; also temperature is not high
Effusiveness = low viscosity + low gas content magma; also, temperature is high
Lecture’s goals:
VOLCANIC ACTIVITY
6_ Compare and contrast 2 of the most important types of volcanoes
2 types:
- Shield volcanoes (mafic)
_ composite (strato-) volcanoes (felsic)
Lecture’s goals:
VOLCANIC ACTIVITY
7_ Describe how volcano type is related to plate tectonics
_ Convergent plates: composite (strato-) volcanoes (felsic)
_ Divergent plates: shield volcanoes (mafic)
Lecture’s goals:
VOLCANIC ACTIVITY
8_ List and describe a selection of volcanic hazards (hint: 3)
1_ fluid material (lava flows)
-> low viscosity lava
2_ pyroclastic material (ash)
-> fast, hot, and a mixture of gas and pyroclastic material
3_ lahars (note: not always associated with an eruption)
-> mixture of water and debris
-> usually follow river channels
