Midterm: Magmatism/Volcanism Flashcards
What is magma?
What is lava?
magma extruded onto the surface
What does texture mean for igneous rock?
refers to the grain size of the constituent mineral crystals making up the rock and is a proxy for their formation environment.
What is phaneritic texture mean?
igneous rocks are those whose mineral crystals are large enough to see, indicating an intrusive (i.e., plutonic) history.
What is aphanitic texture?
igneous rocks are those whose mineral crystals are too small to see, indicating an extrusive (i.e., volcanic) history.
What is porphyritic texture?
igneous rocks have a mix of large mineral crystals surrounded by a matrix of fine-grained material, indicating a multi-stage cooling process.
What is the composition of an igneous rock mean?
refers to the chemical and mineral make-up of a rock.
What does an igneous rock’s composition control?
secondary properties such as density, melting temperature, and viscosity.
What is mafic composition?
High in Mg and Fe and low in Si. Mostly made of minerals like olivine, pyroxene, and plagioclase feldspar.
What is felsic composition
High in Si and low in Mg and Fe. Mostly made of minerals like quartz, alkali feldspars, and plagioclase feldspar
How does igneous rock form?
igneous rock forms when molten rock, called magma, cools and solidifies, either below the Earth’s surface (intrusive) or when it erupts onto the surface as lava and cools rapidly (extrusive) - essentially, the process of crystallization of melted rock creates igneous rock.
How does melt form?
- Increase temperature (hot spot melting)
- Decrease pressure (decompression melting)
- Add water or other volatiles (flux melting)
