GEOL 105- Exam 2

Mineral

Naturally occurring

Inorganic

Solid

Specific chemical composition

Orderly Internal Crystal Structure

Element

most fundamental substance that matter can be separated into chemically

What is the smallest component of an element?

atom

neutron

subatomic particle with a mass of 1 and a charge of 0

proton

sub-atomic particle with a mass of 1 and a positive charge

electron

sub-atomic particle with a mass of 1 and a negative charge

covalent bonding

bond between two atoms in which electrons are shared

ionic bonding

bond in which electrons are transferred from one atom to another, thus forming ions

Why do atoms bond?

an atom seeks to have a full outer shell to be atomically stable. it's accomplished by transferring or sharing electrons with other atoms

Physical Properties used to Identify Minerals

Color and Streak	Crystal Structure
Luster	Specific Gravity and Density
Magnetism	Fluorescence
Hardness	Effervescence
Cleavage/Fracture	Smell and Taste

What mineral

• fizzes when it reacts to a weak acid

• tastes like salt- because it is salt!

• smells like rotten eggs

sulfur

What is Moh’s Hardness scale?

A scale that ranks minerals based on their ability to scratch another mineral or be scratched, ranging from 1 (talc) to 10 (diamond)

What is the hardness of a fingernail?

2.5

What’s the hardness of a glass plate?

5.5

Cleavage

breaks along smooth planar surfaces (along directions of weak bonding)

Fracture

breaks along irregular surface, or smooth curved surfaces

Does glass have cleavage or fracture?

It has conchoidal fracture

silicon-oxygen tetrahedron

Basic building block of silicate minerals

One Si4+ cation surrounded by four O2- anions

Forms the shape of a tetrahedron

An important characteristic of them is their ability to join together to form more complex structures

Two join together by sharing an oxygen anion

Isolated/Nesosilicate tetrahedra

most basic type of silicate

no sharing of oxygen between tetrahedrons

individual tetrahedra linked to each other by bonding to cation between them

Overall negative charge

Positive cations fit in interstitial zones that act as a weak glue to bind silica tetrahedron

No apex oxygens shared within this type of silicate mineral at atomic scale

Randomly distributed in any orientation

Fact that there’s no shared oxygen- tends to leave them susceptible to weathering and breakdown

Single chain silicates

Crystal structure that is somewhat more ordered

Share 1 apex oxygen

Form chains that still have positive cations that weakly chain them together

Less resistant to weathering than more structured silicates that would have additional shared oxygen

More durable than nesosilicates

Positive cations are present- loosely bond the chains together

Double chain silicates

Chains are now linked together by sharing oxygen in

central position

Positive cations are still present in the interstitial zone (middle)

More durable than the first two

Phyllosilicates/sheet silicates

Base of tetrahedrons fall in one plane and apex in another

Corner oxygens on base are linked to other silica tetrahedron

Forms a sheet-type structure

Positive cations/electrostatic charge can join one sheet to an adjacent
sheet- But can easily be pulled apart

Tectosilicates/framework

all the corner/apex oxygens are connected to an adjacent tetrahedra

More resistant to weathering than the others

forms a more complex structure

isotopes

a form of an element that differs from other forms because it has a different number of neutrons

compound??

substance composed of many identical molecules containing atoms from more than one chemical element held together by chemical bonds

energy levels??

2, 8, 18, 8???

idk- 2 in the first and 8 valence electrons

ion

an atom that has either gained or lost electrons and has thus become charged

van der Waals bond

Layers of covalently bonded carbon atoms-

very strong within sheet themselves, but in between layers- interstitial zone- weak attractive force that holds layers together

Ex: Chunk of graphite- draw like a pencil- leaving covalently bonded layers on paper, breaking of interstitial layers

luster

character of reflected light

Two basic types- metallic and nonmetallic

(Does the mineral have the look of a metal or not?)

streak

the mark left on a porcelain plate when a mineral sample is ground to a powder by being rubbed across the plate

hardness

Resistance to scratching

effervescense

escape of gas from an aqueous solution and the foaming or fizzing that results from that release

sulfur??

crystal form

distinct shape that crystal forms

Multifaceted structure

fluroescense

emission of light by a substance that has absorbed light or other electromagnetic radiation

specific gravity

ratio of mineral’s weight to weight of an equal volume of water

(essentially the same density in g/cm3)

Typical minerals/rocks- around 2.5

Often associated with metals or metal ores

silicates

minerals that contain silicon (Si4+) and oxygen (O2-)

Make up over 85% of the mass of the crust

Dominant component of most rocks

Over 1000 silicate minerals have been identified and described

What is the rock cycle

the series of processes through which rocks are transformed from one type to another

Visually illustrate how the 3 primary rocks relate together

Geologic material gets recycled over and over and over and over…

Various earth materials- rocks and minerals

Processes that cause earth materials to

Move and/or change

Because its a cycle- no beginning or end really

There are a number of possible pathways that earth materials can follow through the rock cycle

igneous rock

a rock formed from the cooling of magma, crystallize from molten material

sedimentary rock

rock that has formed by the lithification of sediments

Most common rocks on earth’s surface

metamorphic rock

hosed rocks lol- messed with over and over and over again- interesting though

Lithification

process by which loose sediment turns into solid

Metamorphism

the transformation of a parent rock into a new rock as a result of heat and pressure that leads to the formation of new minerals, or recrystallization of existing minerals, without melting

magma

molten rock that flows within the earth, typically dominated by silica

lava

molten rock that has reached the Earth’s surface

Cools quicker because its on the surface

how does the rate of cooling affect crystal sizes in igneous rocks

fast- small

slow- large

mixed cooling history- mixture of grain sizes

What are the different igneous rock textures

phaneritic

aphanitic

porphyritic

Bowen’s Reaction Series- significance to metling and crystallization, and magma composition

Minerals that crystallized last melt first and vice versa

Both mafic and felsic rocks can crystallize from an originally mafic magma

Minerals that form early can react with magma to form new minerals

Or earlier formed minerals may be removed from the system

Magmatic differentiation/fractional crystallization

how does this process affect the chemical compostion of a magma

mini convection cells

Composition of magma changes as solidified crystals are removed from mixture

Cracks act as a strainer- minerals are filtered out and changes the percentage of certain minerals

viscosity

a measure of a fluid's resistance to flow, which is influenced by the fluid's composition and temperature

how is viscosity related to temp and/or silica content of a magma/lava

higher temp and/or lower silica content- less viscous/runny

lower temp and/or higher silica content- more viscous/thicker

How does viscosity impact the explosiveness of volcanic eruptions?

high viscosity- more explosive, gas trapped

low viscosity- less explosive/effusive

Mafic rocks

Intrusive- gabbro

Extrusive- basalt

magnesium and iron rich minerals

Intermediate rocks

Intrusive- diorite

Extrusive- andesite

sodium and aluminum-rich minerals

Felsic rocks

Intrusive- Granite

Extrusive- Rhyolite

feldspar and silica-rich minerals

What is the intrusive ultramafic rock?

Peridotite

sill

an igneous intrusion that is parallel to existing layering in the country rock

dike

cuts through preexisting layers of surrounding rock

other intrusive igneous bodies

batholith, laccolith, lopolith, plutons, volcanic necks, magma diapirs

Active Volcanoes

erupted within historic time (600)

Dormant Volcanoes

hasn’t erupted in last few thousand years, but has potential to be active again

Extinct Volcanoes

hasn’t erupted for 10s of thousands of years and not expected to again

Where are the majority of Earth’s volcanoes located? Why?

plate boundaries- more activity

specifically, the ring of fire- pacific plate is mostly subduction zones

What type of magma is more explosive?

felsic- lower temps and higher silica content

How does viscosity/temperature affect the way mafic and felsic magmas cool?

Felsic tends to be more explosive because of lower temp, higher viscosity- cools first because “less ground to travel“ in terms of temperature

Mafic tends to be effusive because of higher temp, lower viscosity

What are some of the formations that basalt can make?

Aa

Pahohoe

where are mafic and felsic magmas/lavas found in terms of plate tectonics?

Mafic- divergent mid-oceanic ridges

Felsic- subduction zones

What are some volcanic hazards?

Can be extremely dangerous- duh

Destruction of property and loss of life

Threat to health

Crop failure

What can we do about volcanic hazards?

be knowledgeable, inform the public, have plans in place, etc.

How can eruption change global climate?

volcanic ash able to create sulfuric acid- contributes to global cooling

also able to reflect radiation

Shield Volcanoes

a low-profile volcano formed primarily from eruptions of low-viscosity mafic magma

Cinder cones

a steep-sided volcano comprised almost entirely of loose rock fragments and typically formed during a single eruptive event

What parts of the US have volcanic activity?

Western plate boundary- Cascade Range

Yellowstone Hotspot

What can be used for predicting volcanic eruptions?

Gas leaks — the release of gases from the magma into the atmosphere through cracks in the overlying rock

Bit of a bulge — the deformation of part of the volcano, indicating that a magma chamber at depth is swelling or becoming more pressurized

Getting shaky — hundreds to thousands of small earthquakes, indicating that magma is on the move

Dropping fast — a sudden decrease in the rate of seismicity, which may indicate that magma has stalled, which could mean that something is about to give way

Big bump — a pronounced bulge on the side of the volcano (like the one at Mount St. Helens in 1980), which may indicate that magma has moved close to surface

Blowing off steam — steam eruptions (a.k.a. phreatic eruptions) that happen when magma near the surface heats groundwater to the boiling point. The water eventually explodes, sending fragments of the overlying rock far into the air.

Is there volcanic activity not on Earth?

Yes

Mars- Olympus mons, shield volcano 27 km high

Jupiter’s moons- strong gravity influence from Jupiter- moon compresses and relaxes- generates heat and formation of subsurface pockets of liquid sulfur and then erupts at surface

Weathering

physical breakdown and chemical alteration of rocks when exposed to air, moisture, organics

Erosion

The process by which gravity, moving wind, water or ice transports the products of weathering from one place to another

Mechanical weathering/disintegration

Breakdown of a rock or mineral into smaller pieces

No change in chem composition

Change in shape and size, but still original material

Increases surface area- more area to be weathered

More area for air or water to interact

Can lead to chemical weathering

Chemical weathering/decomposition

Involves chemical breakdown through various chemical reactions

Taking preexisting minerals and changing it into something else- feldspar to clay mineral

Typically- taking unstable mineral to form a more stable mineral

Types of Mechanical Weathering

frost wedging, frost heaving, solidification, thermal expansion and contraction, pressure release, abrasion, plant roots, animals

Types of Chemical Weathering

hydration, hydrolysis, dissolution/leeching, oxidation

Compaction

DOG PILE!!- if on the bottom- you’re feeling the compaction of the weight on top of you

Cementation

the process by which minerals are precipitated between grains in sediments

Rock

aggregate of one or more minerals

Phaneritic

a rock texture in which the individual crystals or grains are visible to the naked eye

large crystals, fast cooling

Aphanitic

an igneous texture characterized by crystals that are too small to see with the naked eye

small crystals, fast cooling

Porphyritic

an igneous texture in which some of the crystals are distinctively larger than the rest

mixed grain sizes, mixed cooling history

Pegmatites

Pegmatitic- many large crystals

Grains over 2 cm

Very slow cooling rate

exceptionally coarse-grained igneous rocks composed of interlocking crystals, with individual crystals usually over 1 centimeter (0.4 in) in size and sometimes exceeding 1 meter (3 ft)

Obsidian

volcanic glass

no crystal structure

cooled instantaneously

Pumice

a highly vesicular felsic volcanic rock (typically composed mostly of glass)

a bunch of ash put together???

Pluton

a body of intrusive igneous rock

Laccolith

concordant intrusion in which the central part has formed an upward dome- muffin top

Batholith

an irregular body of intrusive igneous rock that has an exposed surface of at least 100 km2

collection of smaller blobs- grandaddy of them all

Highlands

rugged, mountainous regions on the Moon’s surface that are characterized by their bright, rugged terrain

Vesicles

small holes left behind after lava cools and turns into volcanic rock

Scoria

dark-colored igneous rock with abundant round bubble-like cavities known as vesicles

Pillow basalts

outer surface hardens in contact with cool water, inner portion remains fluid and breaks through crust at the end

left with ropey, pillow-like structures

occurs on the seafloor

lava tubes

a tube that forms as mafic lava flows along a channel and lava leveés build up on either side, eventually forming a roof (once a lava tube forms it insulates the flowing magma, allowing it to stay hot a liquid for longer and therefore flow much further)

very big and does not always occur under water

pyroclastics

volcanic material formed during an explosive eruption

tephra

fragments of volcanic rock (including volcanic ash) ejected during an explosive eruption

volcanic dust

very fine volcanic ejecta; about the consistancy of flour