Test 1 Flashcards
Stationary Hotspot model
Pacific plate moved northwest over stationary hotspot creating island chain.
Mobile hotspot theory
Southward moving hotspot supported by paleolatitude studies- decrease in latitude as rock becomes younger.
Hotspot
Exceptionally hot long lasting volcanic region generated by underlying mantle magma often thought to be catalyzed by tectonic plate movement.
Mantle plumes
Upwelling of hot mantle rock largely due to density differences that are the source of hot spots.
Age of Big Island/ trend of volcano ages in chain
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Know locations of volcanoes on Big Island of Hawai’i
SEE MAP
Elevations of 3 largest volcanoes on Big Island
Mauna Kea- 13,796; Mauna Loa- 13,677; Hualalai- 8,271
Hawaiian Volcano Observatory
Located on rim of Kilauea Caldera on the Big Island. Initiated to study active volcanoes on the Big Island for safety. Originally directed by Thomas A. Jagger.
Kilauea structure
Subaerial surface is in the form of a gently sloping, elongate, decentralized shield.
Kilauea’s summit features
Kilauea summit cauldera and Halemaumau crater.
Other important Kilauea features
Eastern and southwestern rift zones.
Hawai’i
Biggest island of Hawaiian volcanic chain.
Hilo
Largest settlement on Hawaii.
Kilauea
Shield volcano- most active on Hawaii- southern shore. 4,096
Mauna Loa
Largest subaerial (mass and volume) on earth. Second most active shield volcano with relatively gentle slopes. 13,677
Mauna Kea
Dormant volcano and highest point in State of Hawaii. Northern part of Big Island. 13,796
Hualalai
Third youngest and third most active on Hawai’i. Western part of island. 8,271
Kohala
Oldest volcano on Hawai’i- shield volcano- gorges cut by extensive erosion.
Loihi
Submarine volcano located of southeast coast of Hawai’i Lies on flank of Mauna Loa.
Pu ‘ u ‘ O o
Largest volcanic cone in the eastern rift zone of the Kīlauea volcano of the Hawaiian Islands- main vent
Mauna Ulu
A large eruption of Kilauea- longest lasting flank eruption of Hawaiian history.
Summit Caldera
Formed at the summit of a volcano either by an eruption or by subsidence of land into a magma chamber.
HVO
Hawaiian Volcano Observatory- monitors Kīlauea, Mauna Loa, Hualālai, and Haleakalā. Implemented to study active volcanoes in close proximity without being in extremely dangerous conditions.
Halema ‘ uma ‘ u Crater
Pit crater located within the much larger summit caldera of Kīlauea. Active crater containing a lava lake.
Lava Lake
Large volumes of molten lava, usually basaltic, contained in a volcanic vent, crater, or broad depression
Pit Crater
Depression formed by a sinking or collapse of the surface lying above a void or empty chamber, rather than by the eruption of a volcano or lava vent.
Kilauea Iki Crater
Pit crater which is next to the main summit caldera of Kīlauea.
Makaopuhi Crater
Largest pit crater on Kilauea.
Types of eruptions
Fissure eruptions, lava fountains, spatter cones, cinder cones, phreatomagmatic
Types of lava flows
Aa and pahoehoe.
Lava flow vs. stream network
Viscosity differences causes different patterns and solidification. Chemical makeup causes crystalization differences.
Active vs. inactive lava lakes
Active- develop at summit or flanks of volcano, top of column of lava
Inactive- stagnant and do not sit at top of column
Conductive cooling
Initial symetric cooling followed by faster cooling of upper crust.
Solidification time equation
t=L2/4b2k; t is time, L is half thickness of sheet, k is thermal diffusivity= .01, b is factor depending on temp differences of magma and wall
Lava flow thickness equation
Volume of total magma/Land area covered.
Kilauea lava compostions
Basaltic shield volcano- tholeiite type of basalt containing mostly mafic minerals- commonly olivine. CaO, MgO, TiO2.
Kilauea lava temperature and viscosity
1150-1170 degrees Celsius and low viscosity causes lava to travel greater distances.
Viscosity and crystallinity r-ship
Higher the viscosity greater the crystallinity
Critical Crystallinity
Point at which lava will crystallize due to mineral/chemical anisotropy.
Factors that determine Aa vs. pahoehoe textures
Aa generally form in open channel and pahoehoe form in insulated tubes. Also- high effusion rate causes Aa and low causes pahoehoe.
Lava tube formation
Stationary solid crust must be present over fluid lava.
Lava flow inflation
Low slopes because they advance more slowly. Upslope lava can advance at a higher rate than the flow front.
Volcanic gases
Water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2)
Magma Chamber Model
Fractional crystallization (commonly olivine first) and gravitational settling to bottom of chamber- melt is more felsic. Bottom remelts and causes to become mafic again.
Problems with magma chamber model
Magma chamber forms by instantaneous emplacement of magma at liquidus temperature; Assumed to be roughly spherical or ellipsoidal; Assumed to be cooler at top and hotter at bottom; Crystallization near roof and settle toward bottom.
Bowens reaction series
DRAW IT OUT.
Formation of Kilauea Iki lava lake
1959 Eruption: 1) Empty crater lying above magma body. 2) 30 million cubic meters drawn from body into crater. 3) Crater drained down to 8 million cubic meters. 4) Eruption ended leaving a net 38 million cubic meters in crater.
Solidification front
Zone where molten magma/lava crystallizes when in contact with cold wall rock.
Zones within an SF
Rigid crust, mush, capture front, suspension, crystal free magma
Why does SF inhibit crystal settling
Crystals growing in the suspension zone are too small to settle. By the time crystals grow large, they are trapped within the SF and cannot seIle.
Rheology of SF
Gradient of solid wall rock to crystal free magma.
Sudbury Igneous Complex
Initial- superheated melt with instantaneous emplacement. Final- No fractional crystallization or settling and heterogenous layers.
Marshian magma chamber model
Spherical magma body with solidification fronts.??
Ferrar Dolerite Sills
Decreasing intrusive age. Basement sill includes tongues of opx while peneplain does not.
Hawaiian Lava Lakes
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Peneplain vs Basement sill
Peneplain has lower MgO content
