Igneous Rocks And Volcanoes Flashcards
Intrusive
slow cooling, large crystals, form when MAGMA crystallizes underground
Extrusive
quick cooling, tiny crystals or glassy, form when LAVA cools and crystallizes on the surface of the earth
Magma
mixture of liquid rock, crystals, and gas, starts out mafic, underground lava
What is a rock?
Solid collection of minerals/crystals/grains that grow or get cemented (stuck) together.
phaneritic
large crystals, intrusive
aphanitic
small crystals, extrusive
porphyritic
mixed, extrusive
other textures
Glassy
Vesicular (holey)
Pyroclastic (made of fragments of volcanic origin)
felsic
- SiO2, feldspar
- light colored: pink, white, grey
- explosive
mafic
- Mg (magnesium), Fe (iron)
- dark colored: green, black, brown
- effusive
Igneous rocks
formed by hardening of lava or magma
pluton
when magma cools in a mass
dyke
when magma comes through existing rock structures
sill
when magma cools between rock layers
some ocean plates
basalt
continental crust
granite
mantle
olivine
pahoehoe
river flow
a’a
all move together
Where do you find magma?
- spreading ocean ridges–>decompression melting
- subduction zone–>2 plates meet, push and then slide past each other, heat up through friction, heat up rock
- hot spot (in Hawaii)–>have mafic magma
What are three ways magma forms?
- heat (with friction)
- water
- release (or decompression melting?)
Igneous rock chart
- classifies ig rx based on two factors: mineral composition and percentage and crystal size
- a line on chart represents a single rock. The line passes through minerals that are in the rock
- match the rock color to the chart, analyze rock for crystal size or texture
Type of eruption depends on
- gas content
- silica content
- viscosity
Gas content
- less gas = effusive + mafic
- more gas = explosive + felsic
