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What is a cirque?
o Bowl-shaped depression or basin at the head of a mt valley, carved out by an alpine glacier
o Usually 1-2 miles across and 500’ to 2500; deep
o Sharp, pointed mountain peak formed by the development of 3 or more cirques
Lake in a cirque
What is a hanging valley?
o Tributary valleys that stand above main valleys – usually get waterfalls
What is the Cascade Range? Where is it?
o The cascade range is the North South range of active and potentially active volcanoes. It is located in the NW United States
How do subduction zones form?
o It is the result of tectonic convergence. 1 plate dives below another plate.
Examples of subduction zones around the world?
o Japan, Andes, and Indonesia
· What two tectonic plates are involved with the formation of the Cascade Range?
o Juan De Fuca Plate subducting beneath the North American plate
· Do subduction zone volcanoes tend to have explosive eruptions or quiet eruptions?
o Explosive eruptions
What are stratovolcanoes/composite volcanoes?
o Large steep sided cones with alternating layers of ashbed and lava flows
o Yes, they are explosive and destructive and dangerous
What are nuees ardentes?
o Glowing hot crap
o It is extremely dangerous
What are the specific hazards of ash eruptions?
o It is very hot ( no shit)
o Contaminates surface water
o The weight of the ash can damage or collapse building
o Lahars are volcanic mudflows that happens during ash eruptions
o H2O (steam )
§ HCl and HF are acids they are corrosive
· Most subduction zone volcanoes & most stratovolcanoes have lavas made up of what specific types of lava rocks? And what are they and their characteristics
§ Andesite and dacite
· Fine grained crystals Cooled quickly
o Aphanitic texture Mix of large and small crystals 2 cooling rates – started off slow then quick cooling Porphyritz texture They are intermediate chem.
§ Pumince: extrusive igneous rock Lots of tiny holes that were gas bubbles in the lava Frothy texture· Its light weight Felsic rock
o Ground heats up
§ Tilt meter
o Ground swelling
o Small earthquakes
§ 100-1000 new small earthquakes
o Change in gas emissions
§ Mix of gases change
o However not all have warning signs
What is a lateral blast?
o an explosive volcanic eruption the ejects material horizontally to one side rather than vertically as most explosive eruptions do.
What triggered the 1980 eruption?
o North side of volcanic had been swelling
o A large hole or depression that formed when a volcano collapses or destroys itself
o What is Mt. Mazama? What type of volcano was it?
o What is rhyolite?
· Extrusive igneous rock
· Interlocking crystals
o Extra small
· Some chemistry and minerals as granite
· When it erupts it is very viscosity
o What is obsidian? What are its characteristics?
· Extrusive ign rock
· Cooled very quickly.
o There is no crystals to it
· Looks like broken glass
o Only rock that is considered glassy
· Usually black
· Smooth curved fractures surfaces
o Conchoidal fracture
o What is volcanic tuff? How does it form? What texture does it have?
Extr igneous rock
o Has a clastic texture
· Solidified deposited of volcanic ash
· Light color or intermediate
o What is scoria? What are its characteristics? What texture does it have?
The mafic version of pumice
· Usually dark gray to dark brown to dark red
o The brown and red are due to oxidation. Gray is the original color
o Frothy texture
· Light weight
· Does not float in water like pumice does
o What is a cinder cone?
Small steep sided cones of loose igneous debris
o When did Wizard Island form?
· It formed after the collapse of Mt. Mazama
o What evidence indicates that the Crater Lake area had glaciers during the last Ice Age (Pleistocene)?
· Glacial scratches, has U shaped valleys and has drifts and settlements
o What two volcanoes are in Hawaii Volcanoes National Park?
Kilauea and Mauna Loa
o What is the largest volcano on Earth?
o What are hotspots? Examples? How do they form? Can hotspots break apart tectonic plates? Do all hotspots break apart tectonic plates?
o Large mantle plumes that emerge at the surface to form volcanoes
o They can break apart tectonic plates but some do not**
o Examples **
§ Afar hotspots (ripping the African plate)
§ Iceland hotspot (North atlantic)
§ Yellowstone hotspot
§ Hawaii hotspot ( Pacific
§ Includes the largest volcanoes on Earth & the Solar System
§ Low and broad profile
§ Composed of numerous lava flows
§ Relatively quiet, non-explosive eruptions
o Hawaii shield volcanoes erupt what kind of lava?
o What are the hazards associated with lava flows?
o Pose rel. low risk to human life but high risk to property
o What are lava fountains?
o Tall fountains or domes of molten rock
o What are lava tubes (lava tunnels)?
o What is pahoehoe lava?
o Lava flows with smooth or ropy top surface
o What is aa lava?
o Lava flows with Sharp jagged top surface
o What is reticulite?
· Thread lace scoria
o Very high porosity basalt glass
§ Will not float in water
o Rapid cooling of basalt lava in rich and dissolved gasses is its origin
o Small raindrop shaped blobs of basalt glass – mafic obsidian
§ Also called achneliths
What is Pele's hair?
o Extremely thin, long threads of basalt glass
o May have 1 or more attached achneliths
o Forms by tiny lava drops get stretched by winds during high fountain eruptions
What is Loihi?
o Volcano on sea floor
o Located 20 miles south of the S shore of Hawaii
o 12000’ above surrounding seafloor
· Where is the highest concentration of geysers and hotsprings anywhere on Earth?
· How many geothermal features does Yellowstone have?
· What type of volcano is the Yellowstone Volcano? (a hotspot)
o Large mantle plumes
· What are the four most common volcanic rocks found in the Yellowstone area?
o Precambrian granite and gneiss or sed or tertiary volcanic rocks
What is rhyolite?
o Felsic, aphanitic, extrusive igneous rock
What is obsidian?
o Felsic, glassy, extrusive ign rock
§ Type of lava and obsidian cliff
What is volcanic breccia?
o Felsic, clastic, extrusive ign rock
o Mix of angular large and small pieces
What is volcanic tuff?
· Felsic, clastic extrusive ign rock
· Formed from explosive volcanic eruptions
· Does the Yellowstone Hotspot have mega-eruptions on a regular basis?
· How often do Yellowstone mega-eruptions occur? When is the next mega-eruption due?
o Every 600-800 KY there has only been 6 of them. 640 KY , 1.3 MY and 2.1 MY
· What is a caldera? How old is the Yellowstone Caldera? How did it form?
o Yellowstone Caldera
§ Each large eruption produced an enormous caldera
§ 40 x 30 miles in size
§ Older calderas occur to the west (snake river plain, Southern Idaho)
· Grand Canyon of the Yellowstone . What rocks are found along the Grand Canyon of the Yellowstone River? What is hydrothermal metamorphism?
§ Most famous and colorful and scenic of YNP’s valleys
· Mostly yellowish colored rhyolite
· Has two large waterfalls
· Rx have been hydrothermally metamorphosed
· Intense alteration by superheated groundwater
· What is obsidian? How does it form? Did it cool quickly or slowly from lava? Is obsidian stable over long geologic time scales? What does obsidian convert to, eventually? What is partially converted obsidian?
o Most famous obs outcrop in USA
o Roaring mt members of the plateau rhyolites
§ Pleistocene about 180,000 years
o Partially devitrified obsidian
o White spots
§ Cristobalite (SiO2)
o Obsidian eventually crystallized to rhyolites
o Snowflake Obsidian
·What is Specimen Ridge?
o Still standing fossil trees/forests are preserved in thick volcanic beds
o 27 layers of fossil forests
o 2000 years elapsed between each forest
o Trees: Redwood, walnut, sycamore, maple, oak, magnolia, dogwood, chestnut
o Volcanic deps here are not from Yellowstone hotspots, but from older volcanoes
§ Absaroka volcanic supergroup
What are fumaroles?
§ Hot steam vents
§ May sprout water when water table is high
§ Sometimes roar (heard over 4 miles away!)
§ Hot springs with boiling mud instead of only water
What are geysers?
§ Other famous ones
· Fountain , morning, great fountain geysers
§ St. johns favorite geyser
· White dome geyser
o (travertine, which is made of calcite - CaCO3; and geyserite/siliceous sinter, which is made of opal - SiO2∙nH2O)
How did the Teton Range & Jackson Hole Valley form?
· The Teton Range is mostly made up of what rocks? These rocks are what age?
· o Mostly Archean granites and gneisses
o Rocks are about 2.5-2.9billion years old
§ Felsic phaneritic intrusive ign rock dom in quartz and k-feldspar
§ Foliated highgrande mtm rock
· What type of sedimentary rock occurs at the very top of Mt. Moran? What is its age?
· What type of unconformity is the Precambrian-Cambrian boundary at the top of Mt. Moran? In what other famous national park is this particular unconformity exposed?
o An unconformity erosion surfaces
o Correlates with the great unc at the top of grand canyons innor gorges
· Sed rock over ign or mtm rx
· About 2 billion years of missing time here
o Mt moran and other mts in the TR have some black vertical stripes
o Planar intrusions that cute across the country rock often vertical and it is thin to thick
· What are horsts and grabens? How do they form? What types of faults occur along the edges of horst blocks and graben blocks? Has the crust been stretched (extended) or squeezed together (compressed)?
o TR is a horst and JHV is a graben
o Formed by crustal stretching get lots of normal faults
o Teton Fault
§ Boundary between the TR horst block and JHV graben block
o Normal fault
§ HW down and FW up
o The park is at the NE most corner of the Basin and Range phys province all horsts and grabens
· What is the Teton Fault? How much fault movement & offset has occurred along this fault?
o The Teton boundary between the TR horst block and the JHV graben block. It like the normal fault. HW down and FW up.
o Teton Range has horns, cirques, arêtes, Ushaped valleys , glacial deposits, and still extant glaciers
o Alpine and continental glaciers covered the area during the Pleistocene ice age
Know the basic elements of the Gros Ventre Landslide story.
o June 1925 large rockslide in the Gros Ventre River Valley just outside of the park
o Several cubic miles of debris blocked the river
o Triggered by an earthquake
o Landslide formed a 5 mile long 200 feet deep lake
o 2 years later the landslide dam eroded and the lake disappeared in a giant flood
o The town of Kelly (5 miles away) was wiped out and 6 people were killed
· What are earthquakes? Where do earthquakes commonly occur?
o Earthquakes are natural shaking or vibrating of Earth by ricks breaking along faults and rapid release of energy. These occur at or near boundaries and at hotspots and in active mountain belt
· How is earthquake intensity measured? What is the Richter Scale? What does it measure? What is the Mercalli Scale? What does it measure?
· Mercalli scale
o Based on description of damage
· Richter scale
o Based on the amount of energy an eq releases
o Number scale (1-10) is 30x more energy release
· * P waves: Push-pull waves travel quickly not very destructive. Primary waves Body wave: EQW that move through solid rockPush pull
· * S waves: Up and down waves; travel slowly ; very destructive. Secondary waves Body wave: EQW move through solid rock
· * Love waves: Horizontal side to side wave at the surface
· * Rayleigh waves: Rotational surface waves
o Shaking of the groud
o Rupture of the ground
o Ground rises /falls
o Ground tilting
o Changes in Geophysical props of rocks
o Changes in nearby geysers eruptions patterns
o Water level changes in wells
o Increase in random gas emissions from ground
o Strange animal behavior
· What & where are the Appalachians? Why are most of the Appalachian Mountains not very tall?
o Quebec to Alabama
o Mt go underground in the Mississippi river area
o Mt re-emerge in the AR OK TX area = Ouachita mt
· How did the Great Smoky Mountains get its name? What is the source of the smoky haze over these mountains?
o Forest receive rain from moist air from the Gulf of Mexico
o Its natural
o Mist and fog in air combine with rising vapors of resins and plant oils (terpenes) creating a smoke effect
o These mts formed by continental collision (1 result of tectonic convergences)
§ Or subduction
§ 2 converging plates with continental lithosphere (thick and light weight)
What is the Taconic Orogeny? When did it occur? What caused it?
o A volcanic island arc collided with eastern N American (late Ordovician to early Silurian
· What is the Acadian Orogeny? When did it occur? What caused it?
o The microcontinent Avalonia collided with eastern North American Late Silurian to devoian
What is the Allegheny Orogeny? When did it occur? What caused it?
o The biggest one- most significant
o Africa collided with E. North America in the Pennsylvanian
o The supercontinent
§ Pangaea formed!
When did Pangaea form?
What happened after each of these mountain ranges was formed?
o Each orogeny was followed by erosion and deposition of lots of sediments
What kinds of rocks & structures are found in the Appalachians?
o Valley and ridge
o Blue ridge
· The basement rocks of the Great Smoky Mountains are composed of what? How old are these rocks?
o Blue ridge is dominated by Precambrian ign and mtm rock
o 1.1 billion years
What is the Ocoee Supergroup? Is it thick? Where were these sediments originally deposited?
o Proterozoic sed roc
§ Ocoee Supergroup – 50000 feet thick stack of sed rock lots of ss and shale dep’d in an ancient ocean trench
§ Has been metamorphosed
· What Paleozoic-aged sedimentary rocks are found in the Great Smoky Mountains?·
· Knox group (Ordovician
o Lots of LS and dolostone (marine)
· Chilhowee group (Cambrian)
· Lots of SS, STS, SH (Marine)
When did Pangaea break apart?
What is a Wilson Cycle?
o The supercontinent cycle (they have formed and broken apart many times in Earth’s history )
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