Download Felsic

Organizing Igneous Rocks
 Sorted by mineral composition and texture
Types of
Magma
Consistency
Composition
Color/Density
Felsic
Thick and slow
Silica
(SiO2)
Light color
& less dense
Mafic
Hotter, thinner, and
more fluid
Iron (Fe) &
Magnesium
(Mg)
Dark color
& more dense
Example
Granite
Pumice
Obsidian
Gabbro
Basalt
Scoria
(1,300 – 2,000oF)
Location of
Magma/Lava
Name
Rate of
Cooling
Texture
Example
Inside crust
(under ground)
Intrusive
Igneous Rock
Slow
Coarse-grained
(large crystals)
Granite
Gabbro
Fast
Fine-grained
(tiny crystals)
Basalt
Extra Fast
Porous or Glassy
(no crystals)
Pumice
Obsidian
Scoria
Above crust
(on surface)
Extrusive
Igneous Rock
(Years)
(Days)
(Hours)
“Volcanic landforms”- Igneous Intrusions
 A rock mass that forms when magma cools inside Earth’s interior.
Also called a pluton
 Reaches Earth’s surface only after uplift and/or erosion.
1. Sills - A sheet of igneous rock that lies parallel to the layer it intrudes.
Forced between rock layers.
2. Dikes - A sheet of igneous rock that cuts across rock layers vertically or a
steep angle. Forced through (perpendicular) to rock layers.
3. Laccoliths - Dome shaped mass of igneous rock. Thick lava that does
not flow easily pushes rock layers upward.
4. Volcanic Neck – the remnant of an extinct volcano.
5. Batholith - Largest of all plutons that form the cores of many of Earth’s
mountain ranges. Exposed through uplift and erosion.