Geology Test 1

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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


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