Geology Exam 2

Solid, inorganic, crystalline structure, naturally occuring, certain/specific chemical composition

Atoms arranged in a specific 3-D pattern (crystal lattice)

Solid, naturally occuring aggregation of one or more minerals. Classified by its origin (environment).

Metamorphic rock- Form when pre-existing rocks change character due to a change in temperature and/or pressure conditions.
Sedimentary rock- Form by cementation or precipitation.
Igneous rock-Forms from molten material.

Minerals have an organized sructure and are of a certain chemical composition. Rocks can be "randomly" oriented and usually contain more than 1 mineral.

Organisms extract ions from the water to make mineral crystals (ex. Corals create aragonite (CaCO3); oysters create calcite (CaCO3))

Simplest repeating unit in a crystal

Salt water evaporation, where magma is cooling, where rock is undergoing metamorphosis, and participating out of groundwater

1. Supersaturation or the precipitation of crystals in water (ex. halite (table salt))
2. Crystalizing in a melt of lava or magma (ex. feldspar, olivine)

Silicon and oxygen; Silicates

1. Streak
2. Color (can vary though)
3. Crystal habit/form/structure
4. Cleavage
5. Specific gravity
6. Special properties
7. Hardness
8. Fracture
9. Feel/texture
10. Luster

Mineral’s tendency to break along flat surfaces, due to planes of weakness in the crystal

Resistance to scratching based on the strength of a mineral's chemical bonds

How the light is reflected (ex. pearly, metallic, vitreous)

Mineral’s color in powdered form

Density of the mineral compared to the density of water

Natural distinctive shape of a mineral; based on how a mineral grows

Diamonds degrade (very slowly) at the surface since they are unstable

Above ground; Underground

Cools at Earth’s surface; Cools underground

Remnant heat from formation of Earth, Ongoing heat generation (Decay of radioactive elements)

1. Areas of partial melting in the crust or mantle
2. Decompression/Pressure release, Flux Melting/Volatile addition, Heat transfer

Pressure is lowered, but it’s still hot underground so a melt forms (ex. continental rifts, and divergent-plate boundaries).

Volatiles lower the melting of hot rock as subduction carries volatiles down into the mantle, melting rock (ex. subduction zone)

Rising magma carries heat with it, raising temperature in nearby crust rock, which then melts (ex. hot spot).

Volcano type

The source rock dictates melt composition, and can be varried. Spectrum between which minerals are in the melt.

Silica tetrahedrons bonded to iron, magnesium, and/or calcium (ex. olivine, pyroxene, amphibole, and biotite)
1. Generally dark colored and more dense
2. Common in oceanic rocks (Ocean crust is mafic)
3. Higher melting temperatures

Silica tetrahedrons bonded to aluminum, potassium, and/or sodium (ex. Quartz, Muscovite mica, Orthoclase feldspar)
1. Generally light colored and less dense
2.Common in continental rocks (Continental crust is felsic)
3. Lower melting temperatures

Ultramafic

Partial melting happens first: not all of the rock melts
Felsic minerals melt at a lower temp, so may start to melt first

Magma melts surrounding rocks, incorporating them into the magma and altering the chemistry of the magma

As melt cools, mafic minerals crystallize first and fall out of the magma; felsic minerals crystallize last.

Blocks that fall into a magma chamber and do not completely melt and are carried by the melt

Lose heat slowly = big crystals. Magma takes longer to cool, so mineral crystals have time to grow larger
Cool rapidly = small crystals

1. When eruptions occur underwater, particularly when there is a relatively low eruption rate
2. Blobs of basalt cooled rapidly by quenching in water as more lava continues to inflate

Composition or magma/lava which it formed from

Industrial use, ore, gems, building blocks of the earth

1. pyroclastic
2. phaneritic
3. aphanitic
4. vesicular
5. glassy

1. Avalanche of hot rock, gas, and ash (500-1000C)
2. Can burn and cover everything in ash (when it cools, it can form tuff rocks)
3. common at composite volcanoes
4. Pompeii

Volcanic ash and pieces of rock (forms rock called Tuff)

1. Mud, rock, water slides of huge volumes caused by by melting snow and ice or water. Can also form from pyroclastic flows when extremely hot, flowing rock debris erodes, mixes with, and melts snow and ice as it travel rapidly down steep slopes.
2. Chaotic masses of rock, soil, ice, and what ever debris is entrained into the flow.
3. These are deadly because they happen quickly and can cover everything in their paths with rocks and other materials from the volcano.
4. Common at composite volcanoes

a. Sheet-like intrusive rock body that follows layering in surrounding rocks [horizontal]

Sheet-like intrusive rock body that cuts across layering in surrounding rocks [vertical]

Bowl-shaped depression atop a volcano; A large depression formed when a volcano erupts and collapses (bigger than crater)
Fill over time to become lakes

Pyroclasts (volcanic blocks and bombs), ash, and gas (ex. CO2, volatiles, and water vapor)

1. Resistance to flow
2. More silica=more viscous (felsic). Less silica=less viscous (mafic)

1. Shield Volcano (ex. Mauna Kea, Hawaii), Strato/Composite Volcano, Cinder Cone (ex. Cinder Cone in San Francisco
Volcanic Field, Arizona)
2. Stratovolcano/composite Volcano (ex. Mt. St. Helens)
3. Shield Volcano

If a volcano produces very fluid lava (low in the compound SiO2, or silica), the magma flows a long distance before it cools, making a flat, shield-shaped volcano. If the volcano produces very sticky magma (high in silica) it tends to have an explosive eruptive style that includes lava, pyroclastic flows, and ash

1. Lava flows
2. Lahars
3. Pyroclastic flows
4. Ash (Tephra)
5. Earthquakes
6. Volcanic gases (can cause acid rain)

1. Medium size
2. Viscous lava
3. Felsic/intermdeiate (high silica)
4. Cooler sometimes
5. Explosive sometimes
6. Thousands of years

1. Leat dangerous, smallest
2. Cinders (gravel sized lava bombs)
3. Usually produced in days/weeks during 1 eruption

1. Biggest, tallest, widest
2. Low viscosity (easy flow)
3. Mafic (low silica)
4. Effusive
5. Thousands of years

Effusive eruptions involve the outpouring of basaltic magma that is relatively low in viscosity and in gas content.
Explosive eruptions generally involve magma that is more viscous and has a higher gas content.

Most along tectonic plate boundaries, some near hotspots

Promote magma buoyancy, accelerating ascent and modulating eruptive dynamics

1. Like tiny particles of silica or volcanic glass that can travel in the atmosphere very far from the eruption site
2. Create eye and upper airway irritation, cause minor to major damage to vehicles and buildings, contaminate water supplies, disrupt sewage and electrical systems, and damage or kill vegetation

Streams of molten rock usually slow speed; Most common Hawaiian hazard

1. Stratovolcano in Skamania County, Washington
2. Large eruption was in 1980; predictedby noticing thousands of small earthquakes, venting steam, and a growing bulge protruding 450 feet (137 m) indicated that magma was rising in the volcano.
3. Volcanic hazards: A high-speed blast leveled millions of trees and ripped soil from bedrock. The eruption fed a towering plume of ash for more than nine hours, and winds carried the ash hundreds of miles away. Lahars (volcanic mudflows) carried large boulders and logs, which destroyed forests, bridges, roads and buildings.
4. Forests were obliterated and rivers followed new courses. More than 150 new lakes and ponds were formed, and existing lakes filled with sediment, flooding their banks

Geological process in which earthen materials are worn away and transported by natural forces such as wind or water

The breaking down or dissolving of rocks and minerals on Earths surface (ex. sunlight, water)

Changes the molecular structure of rocks and soil (dissolution, hydrolosis, and oxidation) (ex. dissolution of calcite in water)

Process that breaks rocks apart without changing their chemical composition (root wedging, frost wedging, abrasion)