Geology Exam 2

Front 1

Igneous Texture

Back 1

Texture is the overall appearance of a rock based on the size, shape, and arrangement of interlocking minerals.

Factors affecting crystal size:
- Rate of cooling
* Slow rate = fewer but larger crystals
* Fast rate = many small crystals
* Very fast rate forms glass.

Front 2

Volcanic Glass Formation

Back 2

- Molten rock ejected into atmosphere
- Cools very rapidly
- Unordered Ion frozen in place before forming orderly crystal structure
- Obsidian is prime example

Front 3

Aphanitic (Fine-Grained) Texture

Back 3

- Rapid rate of cooling
- Microscopic crystals
- May contain vesicles (holes from gas bubbles)

Front 4

Phaneritic (Coarse-Grained) Texture

Back 4

- Slow cooling
- Large, visible crystals roughly equal in size
- Felsic, Intermediate, or Mafic

Front 5

Porphyritic Texture

Back 5

- Minerals form at different temperatures.

- Large crystals (phenocrysts) are embedded in a matrix of smaller crystals (groundmass).

Front 6

Pyroclastic Texture

Back 6

- Fragmental appearance produced by violent volcanic eruptions

- Often appear more similar to sedimentary rocks

Front 7

Pegmatitic Texture

Back 7

- Exceptionally coarse-grained

- Form in late stages of crystallization of granitic magmas

Front 8

Vesicular Texture

Back 8

Voids Left by Gas Bubbles

Front 9

Igneous Relations

Back 9

Aphanitic --> Phaneritic
----------------------------------
Rhyolite ----> Granite
Andesite ---> Diorite
Basalt--------> Gabbro

Front 10

Know How The Igneous Rocks Form

Back 10

Intrusive

Extrusive

Front 11

Bowens Reaction Series

Back 11

- Minerals crystallize in a systematic fashion based on their melting points.

- During crystallization, the composition of the liquid portion of the magma continually changes.

Front 12

Bowens Reaction Series
(Review Chart in Lab Book)

Back 12

Lowest Temperatures to Highest:

Felsic (Granite/Rhyolite)
- Lowest Temperature
- Potassium Feldspar/ Muscovite/Quartz

Intermediate (Diorite/Andesite)
- Plagioclase Feldspar/Amphibole/Biotite

Mafic(Gabbro/Basalt)
- Pyroxene/Plagioclase Feldspar

Ultra-Mafic (Peridotite/Komatite)
- Olivene

Front 13

Polarizing Microscope

Back 13

The polarizing microscope was originally developed
for investigating crystalline structures within rocks and
minerals.

Front 14

Most Abundant Minerals

Back 14

Earth's Mantle
- Olivene

Earths Crust
- Feldspars

Front 15

Assimilation

Back 15

Incorporating foreign rock into a magma body

Front 16

Partial Melting
Decompression Melting
Flux Melting

Back 16

Partial Melting
- The incomplete melting of rock, a process which produces most magma.

Decompression Melting
- It requires more heat to melt rock at higher pressures and lower heat to melt rock at lower temperatures
- When rocks melts as a result of the pressure being reduced it is called decompression melting
- Typically occurs along diverging plate boundaries like a mid-ocean ridge

Flux Melting
- The more water present the lower the melting temperature (Remember Sugar Melting Lab)
- Occurs at subduction zones (Converging Plate Boundaries)

Front 17

Magma Mixing

Back 17

Occurs when one magma body intrudes on another magma body having a different composition

Front 18

Mount Saint Helens

Back 18

?

Front 19

Hawaiian Lava Flows

Back 19

AA
- Slow moving, Jagged Blocks, Sharp Edges

Pahoehoe
- Slow Moving, Smooth Surface, Braided Ropes

Front 20

Types of Volcanoes - Cinder Cone

Back 20

- Built from ejected lava (mainly cinder-sized) fragments
- Steep slope angle
- Rather small size
- Frequently occur in groups

Front 21

Types of Volcanoes - Composite cone (Stratovolcano)

Back 21

- Most are located adjacent to the Pacific Ocean (e.g., Mount Fujiyama and Mount St. Helens).

- Large, classic-shaped volcano (thousands of feet high and several miles wide at base)

- Composed of interbedded lava flows and layers of pyroclastic debris

Front 22

Types of Volcanoes - Shield

Back 22

- Broad, slightly dome-shaped
- Composed primarily of basaltic lava
- Generally covers large areas
- Produced by mild eruptions of large volumes of lava
- Mauna Loa in Hawaii is a good example.

Front 23

Viscosity

Back 23

Measure of a material’s resistance to flow (e.g., higher viscosity materials flow with great difficulty).

Factors affecting viscosity
1. Temperature—Hotter magmas are less viscous.

2. Composition—silica (SiO2) content
– Higher silica content = higher viscosity (e.g., felsic lava such as rhyolite).

- Lower Silica content = lower viscosity or more fluid-like behavior (e.g., mafic lava such as basalt)

Front 24

Factors of Explosive Volcanoes

Back 24

1. Temperature of the magma

2. Composition of the magma - Viscosity

3. Dissolved gases in the magma
- Gases expand within a magma as it nears Earth’s surface due to decreasing pressure.

- The violence of an eruption is related to how easily gases escape from magma.

Front 25

Types of Eruptions

Back 25

Pyrocastic Flows
- Very fast moving lava flows which are explosive

Hawaiian Flows
- Slow moving AA and Pahoehoe

Lahars: Mudflows
- Fast moving mud flows

Fissure Eruptions and Lava Plateaus
- Fluid basaltic lava extruded from crustal fractures called fissures (e.g., Columbia River plateau)

Front 26

Volcanic Features (Memorize Picture and Fill in Blanks) Page 129

Back 26

Tabular Intrusive
____________________________________
Dikes - cut across bedding surfaces
Sills - run horizontally to bedding surface

Massive Intrusive
__________________________________________
Lacolith
-Similar to a sill. Lens or mushroom-shaped mass. Arches overlying strata upward

Batholith
- A batholith is a large emplacement of igneous intrusive rock that forms from cooled magma deep in the Earth's crust

Front 27

Volcanic Features (Memorize Picture and Fill in Blanks) Page 129

Back 27

Pluton - Structures that result from the emplacement of magma into preexisting rocks

Volcanic Necks - Pipes are short conduits that connect a magma chamber to the surface

Front 28

The Role of Convection

Back 28

Driving force behind moving plate tectonics. (Lava Lamp Example)

Heat rises and begins cooling near top. Eventually will cool down and sink again. The cycle continues repeatedly.

Front 29

How Sedimentary Rocks Form

Back 29

- Weathering begins the process (Wind, Water) breaks apart particles (Igneous, Metamorphic, and Sedimentary Particles)

- Transported from source location to final resting placing via wind, water, and gravity

- Forms layers at final resting place and eventually are lithified by compaction or cementation.

Front 30

How Sedimentary Rocks Classified

Back 30

- Detrital Sedimentary Rocks
*Accumulation of solid particles derived from both mechanical and chemical weathering.

- Chemical Sedimentary Rocks
* Soluble material produced largely by chemical weathering.
* Ion is solution precipitated by inorganic or biologic processes.

- Organic Sedimentary Rocks
* Coal is primary example
--> Formed by remains of plants that have died and accumulated on the floor of a swamps

Front 31

What does grain size tell us?

Back 31

- Help distinguish detrital rocks

- How the particles in the rocks were transported
* Larger particles carried by great energy like flood while fine particles are carried by wind like in sand dunes

Front 32

Chemical Formula For Chert and Limestone

Back 32

Limestone
- Compose mostly of calcite (CaCO3)

Chert
- Composed of Microcrystalline Quartz (SiO2)

Front 33

Sedimentary Cements

Back 33

Cementation is the most important process in which sediments are converted into sedimentary rocks. Most common cements are:

* Calcite - Fizzes on acid test
* Iron - Orange/Reddish in Color
* Silica - Is the hardest cement

Front 34

What is Lithification?

Back 34

Process in which sediments become sedimentary rocks. Processes include:

* Compaction - sediments accumulate into layers which create enormous weight which compacts the sediments into rocks

* Cementation - See Above Card

Front 35

What is Diagenesis?

Back 35

All chemical, physical, and biological processes that take place after sediments are deposited and during and after lithification.

Front 36

Stages of Coal Formation (Memorize Diagram)

Back 36

Peat
* A soft brown material in which plant structures are still visible

Lignite
* Light burial results in light compaction which turns peat into lignite, a soft brown coal

Front 37

Stages of Coal Formation (Memorize Diagram)

Back 37

Bituminous
* Deeper burial results in heavier compaction which produces Bituminous Coal

Anthracite
* Metamorphosed version of bituminous coal which is very hard, black, and shiny.

Front 38

Conglomerate vs Breccia

Back 38

Conglomerate
* Large gravel sized pieces of rounded rock which means it has been weathered

Breccia
* Large gravel pieces of angular rocks which means that it settled close to its source

Front 39

Environments of Deposition
(Not Enough Info... Too much info to sift through... Sorry!)

Back 39

Three Types of Sedimentary Environments:

*Continental

* Marine

* Transitional (Shoreline)

Front 40

Role of Water Velocity

Back 40

- Fast water velocity results in larger particle sizes.

-Water with no velocity results in fine grained particles that are tough to see with the naked eye.