Geology Lecture Test 2
Terms
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- Molton rock ON surface
- Lava
- Molton rock BELOW surface
- Magma
- 4 Heat sources for melting rock
- Temperature increase with depth, frictional heat from plates moving, decay of radioactive minerals, mantle plumes
- Does increasing pressure cause melting temperature to increase or decrease?
- Increase
- What does water make the melting temperature do?
- Decrease
- What is the primary constituent of magma?
- Silica
- Felsic Magma
- high in silica, thick and pasty, doesnt flow and is very explosive
- Where does Felsic magma form?
- Convergent PB
- Mafic Magma
- silica poor, high in Fe/Mg and flows easily
- Where does Mafic Magma form?
- subduction zones
- What controls magma/ viscosity?
- silica content and temperature
- Intermediate magma forms where?
- convergent pb and subduction zones
- Where are ferromagnesian silicates located?
- the discontinuous side
- Where are plagioclase silicates located?
- the continuous side
- Which side does one mineral change to another at a specific temperature?
- discontinuous side
- Which side does basic feldspar crystal remain the same?
- continuous side
- Crystal Settling
- FeMg minerals fall to the bottom of the magma chamber
- Assimilation
- melting the country rock
- Enchanted Rock
- Batholith
- intrudes parallel to sedimentary rock layers
- sill
- cuts across sedimentary rock layers
- dike
- Devil's Tower and Shiprock
- volcanic neck
- intrudes in a mushroom-like shape between sedimentary layers
- laccolith
- What determins magmas ability to erupt?
- viscosity and gas content
- Which type of magma rises and erupts at the surface?
- Mafic magma
- Whcih type of magma cools underground to form plutonic rocks?
- Felsic magma
- Most abundant gas relased and blows magma apart
- water vapor
- first gas to fizz out of magma
- carbon dioxide
- Pahoehoe
- lava flow with a ropy surface
- Aa
- lava flows as rough, jagged blocks
- Columnar joining
- laval flow cools and shrinks forming hexagonal columns
- Nuee Ardente
- pyroclastic flow that rushed down slope at hurricane speeds in an incandescent flowing cloud
- Where is a Nuee Ardente common?
- Composite Cones
- Lahar
- mudflow that is the deadliest hazard
- Shield Volcano
- low, rounded profile and mafic lava erupts quietly
- cinder cones
- formed by pyroclastics falling around the vent
- Composite Volcanoes/Stratovolcanos
- MOST COMMON, both pyroclastic and laval flows, forms at convergent pb and subduction zones
- Crater
- bowl shaped pit centered over the vent at the top of a volcano
- Lava domes
- formed by silica lava that is to thick to flow and extrudes out over the vent
- Caldera
- depression formed by the collapse of "cone" into the empty magma chamber below
- What does the most catastrophic event on earth form?
- A caldera
- Resurgent Caldera
- formed by renewed surges of magmat into a caldera
- 3 examples of a resurgent caldera
-
yellowstone
long valley, CA
Valle Grande, NM - Fissure Eruptions
- type of eruption that flows out of a long crack
- Example of a fissure eruption
- Columbia River Plateau
- Last Gas to fizz out of magma
- water vapor
- Welded tuff
- Name of the ash flow deposits that erupted from fissures during caldera formation
- 4 ways to predict an eruption
- Plate tectonic locations, harmonic tremor, physical and chemical changes, eruptive history
- Circum-Pacific Belt
-
ring of fire
where most the the volcanoes in the world are located - Weathering
- involves the physical breakdown and alteration at/near the surface
- Erosion
- involves transportation by wind, water, glaciers, etc.
- Differential weathering
- non homogenous rocks weather into bizarre sandstone forms
- Mecahnical weathering
- rocks decomposed by alteration of parent rock (rock change)
- Name mechanical weathering processes
-
1) frost action
2)preserve release
3) thermal expansion and contraction
4) root wedging
5) activities of organisms - Exfoliation domes
-
formed when batholiths undergo pressure relase
(large rounded areas) - Dissolution
- a part of chemical weathering where water removes ions from rocks and carries them in solution
- Carbonic acid
- formed by water and carbon dioxide
- Oxidation
-
when Fe and Mg silicates are chemically altered. FeMg silicates combine with oxygen to form an acid.
If water is present - Limonite - Hydrolysis
-
Weathers potassium feldspar. The end result is 1) clay
2)silica
3) potassium in solution - Bowen's Reaction series least and most stable
-
Least- Olivine
Most - Quartz - Spheroidal weathering
- edges and corners of angular rocks weather into rounded boulders
- Soil regions
- climate is the most important factor of formation
- Major Soil Types
-
1) pedalfers - Fe and Al oxides present, good agricultural soil
2) Pedocals - arid, evaporating waters enrich in CaCO3
3) Laterites - tropical, only deep red A horizon, slash & burn - Lithification
-
Changes sediment into rock by two processes
1) compaction - weight of overlying rock
2) Cementation - minerals precipitated in pore spaces binding particles together - Most common clastic rock
- Quartz sandstone
- Most common chemical rock
- Limestone & dolostone
- Transression
-
Sea level rising
Sequence:
limestone-shale-sandstone - Regression
-
sea level falling
Sequence:
sandstone-shale-limestone - When are sedimentary structures formed?
- at the time of deposition
- What do sand dunes in deserts show?
- Cross bedding
- Symmetrical ripple marks
-
waves going back and forth
Know the picture - asymmetrical ripple marks
-
currents in one direction
know the picture - Mudcracks
- formed by drying out and shrinkage of clay
- Where are fossils found?
- Sedimentary Rocks
- What is coal composed mainly of?
- Carbon
- Steps in forming coal
-
1) swams rich in plant life
2) plants accumulate slowly and form peat
3) decompose in an oxygen poor environment
4) undergo heat and pressure - What is hydrocarbon composed of?
- Hydrogen and Oxygen
- List steps for hydro carbon formation
-
Accumulation of algae and microorganisms in shallow seas
burried quickly by silt/mud
oxygen deficient envoronment so doesn't rot
heat and pressure forms - Vesuvius, Italy
-
79 AD
Destroyed Pompeii and Herculaneum
Subduction of African plate under European plate - Krakotoa, Indonesia
-
loudest noise recorded in history
Tsunami killed 36,000
Located in Circum-Pacific Belt - Tambora, Indonesia
-
Larges and deadliest eruption
"year without a summer"
Gloomy weather set mood for frankenstein
Located in Circum-Pacific Belt - Paricutin, Mexico
-
Cornfield volcano
studied birth to death
cindercone
Subduction of Cocos plate under N. American plate - Mount Pelee, Martinque
-
St. Pierre - town wherenuee ardente killed 28,000 villagers
Killed voters
Subduction of N. American plate under caribbean plate - Heimaey, Iceland
-
Control lava flow - saved town & port
Divergent plate motion along Mid-Atlantic ridge - Lake Nyos, Cameroon, Africa
- cloud of carbon dioxide killed villagers and cattle
- Cascades
-
active and sit above subduction zone
-Erupt andesite
-Subduction of Juan de Fuca plate under N. American plate - Mt. Rainer, Washington
-
Most dangeroud volcano in U.S.
-Lahars will reach populated areas of Pugent Sound - Mt. St. Helens
-
erupted in 1980
millions of trees blown down
spirit lake changes
Hazards- Nuee Ardente, ash, lahar, and avalanche - Mt. Shasta, Cal.
- Largest volcanoe
- Crater Lake, Oregon
-
Mt. Mazama - volcano that erupted
Formed a caldera - Valle Grande, NM
-
Resurgent caldera
Resurgent caldera on w. side of Rio Grande rift
Anasazi carved homes
Bandelier tuff - Long Valley, Cal.
-
Resurgent caldera
Most likely to have major eruption and most active volcanic area
Warning signs - dome swelling, fumaroles and hot springs, earthquakes, carbon dioxide kills trees - Yellowstone, Wyo.
-
resrugent caldera
Sits above a hotspot
erupted 3 times
Warning signs - mud pots, geysers, carbon dioxide kills forest and animals uplift/subsidence of ground, earthqueakes - Alaska
-
2nd most active area in the world
Subduction of Pacific plate under NA plate