Geology Test 1
Describe Mafic. Is it intrusive or extrusive?
45-85% dark silicates comprise oceanic crust and many volcanic islands Extrusive
Describe Ultramafic. Is it intrusive or extrusive?
< 85% dark silicates Either all black or green Intrusive
Define Pyroclastic texture
Forms from the consolidation of individual rock fragments ejected during explosive eruptions (extrusive)
What is the difference between light and dark silicate minerals?
Light are light in color and Dark are dark in color (or green)
Which, light or dark, silicates are common in continental crust? oceanic crust?
Light in continental crust and Dark in oceanic crust
What are the main components of molten rock?
Liquid, Solids, and Volatiles
What is a rock?
solid mass of minerals or mineral-like matter that occurs naturally
Define Geology
study of earth
How are Metamorphic rocks formed?
"changing" preexisting igneous, sedimentary, or other metamorphic rocks
What is the difference between hypothesis and theory?
- Hypothesis is tentative (untested) and offers a ways to tests a scientific question - Theory is well-tested and widely accepted
What are the three types of rocks?
- Igneous - Sedimentary - Metamorphic
Describe Felsic. Is it intrusive or extrusive?
- Mostly light - < 25% dark silicate minerals - Major constituent of continental crust - Extrusive
What are the four composition groups?
1. Felsic 2. Intermediate 3. Mafic 4. Ultramafic
What are the physical properties of minerals?
1. Luster 2. Color 3. Streak 4. Hardness 5. Cleavage 6. Specific Gravity 7. Reaction to acid 8. Crystal Form
What are a few ways minerals form?
1. Precipitate out of fluid 2. Crystallization of Molten Rock 3. Deposition as a result of biological processes
Describe the scientific method process/steps
1. Purpose 2. Research 3. Hypothesis 4. Experiment 5. Analysis 6. Conclusion
Describe a minerals properties
1. naturally occurring 2. inorganic (generally) 3. solid substance 4. specific chemical composition 5. with an orderly arrangement of atoms and crystalline structure
Describe Intermediate. Is it intrusive of extrusive?
25-45% dark silicate minerals "salt and pepper" Extrusive
How old is the earth?
About 4.5 billion years
Describe Basalt
Aphanitic texture Most common oceanic igneous rock Most common extrusive igneous rock (Mafic)
Why do some minerals cleave while others fracture?
Bonds among the atoms within a mineral may not have the same strength
Define Pegmatitic texture
Coarse grained texture Intrusive
What is the difference between a cleavage and conchoidal fracture?
Conchoidal differs because the broken surface is not a smooth, flat plane
How are Igneous rocks formed?
Cooling and solidification of molten rock
What are the seven textures of igneous rocks?
Glassy, Porphyritic, Phaneritic, Vesicular, Pyroclastic, Aphanitic, Pegmatitic
Who proposed the Principle of Uniformitarianism?
James Hutton
What are the two types of Luster?
Metallic and Nonmetallic
Define Aphanitic texture
Microscopic crystals and rapid rate of cooling (extrusive)
How are silicates formed?
Molten rock cooling and crystallizing
Is color a diagnostic physical property
No
What are the two most abundant elements in the earth's crust?
Oxygen and Silicon
What is the unit cell of a silicate mineral called?
Oxygen tetrahedron
Describe Granite
Phaneritic texture Most common continental crust igneous rock Most common intrusive igneous rock (Felsic)
How are Physical and Historical Geology different?
Physical - material composing earth and geological processes Historical - origin of Earth and its development thru time
What are the two main divisions of Geology?
Physical and Historical Geology
Define Glassy texture
Rapid cooling and atoms are frozen in place before they can bond in an orderly crystalline structure (extrusive)
How did Uniformitarianism change how Geologists think?
Required us to think of the Earth as VERY old
Which mineral class makes up most of Earth's crust?
Silicates
What are the two mineral classes of rock-forming minerals?
Silicates and Non-Silicates
Define Uniformitarianism
Slow, gradual observable change - erosion, movement of tectonic plates and catastrophic events
What is a unit cell?
The basic building block of a mineral crystal
What are the potential pathways in the rock cycle?
They can all turn into each other
Define Vesicular texture
Usually aphanitic rock that contains voids left by gas bubbles
Define Phaneritic texture
Visible crystals seen with naked eye and slow cooling (intrusive)
How are Sedimentary rocks formed?
Weathering of preexisting rocks
Define Luster
appearance of a mineral in reflected light
Define streak
color of a mineral in powdered form
Define color
come on dude
Define groundmass
compact, finer-grained material in which crystals are embedded in a porphyritic rock
Define specific gravity
density of a mineral (how heavy it feels)
Define Volatiles
dissolved gases in molten rock
Define reaction to acid
dude come on
What are the differences between extrusive and intrusive igneous rocks?
extrusive on surface of earth from lava intrusive formed from cooling magma within earth
Define Porphyritic texture
large crystals embedded in a groundmass, a matrix of smaller crystals (intrusive followed by extrusive)
What is crystallization?
magma get cold atoms then be friends (bond)
How does magma differ from lava?
magma underground lava aboveground
Define crystal form
mm hm
Define hardness
resistance of a mineral to abrasion of scratching
Define tenacity
resistance to breaking, bending or deformation
Describe Mohs Scale
scale of hardness used in classifying minerals from 1-10
Igneous rocks are composed predominately of which rock-forming mineral class?
silicate
Define cleavage
tendency of a mineral to break along planes of weak bonding (produces smooth flat surfaces)
The name of an igneous rock is based on which two things?
texture and composition
Define Phenocryst
the large crystals, are embedded in a groundmass, a matrix of smaller crystals
How do igneous rocks form?
when hot molten rock crystallizes and solidifies
