page 160. daily question at which type of plate boundary would you find mafic igneous rocks?...
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Page 160
Daily QuestionDaily Question
At which type of plate boundary would you find mafic igneous rocks? Explain
Would the rocks be basalt, gabbro, or could both rock types occur? Explain
Plate Tectonics and Igneous RocksPlate Tectonics and Igneous Rocks
Fig. 6.6
Ophiolite ComplexOphiolite Complex
Oceanic CrustMarine Sediment
Pillow BasaltsSheeted Dikes
Gabbro
Pillow Basalts in the OceanPillow Basalts in the Ocean
Pillow Basalts on the ContinentsPillow Basalts on the Continents
Sheeted DikesSheeted Dikes
GabbroGabbro
Plate Tectonics and Igneous RocksPlate Tectonics and Igneous Rocks
Fig. 6.6
Cinder ConesCinder Cones Built from ejected lava
fragments Have steep slopes
(controlled by angle of repose – the steepest angle at which material remains stable)
Small – 300 m (1000 ft) high, 2 km in diameter
Composite Cones - Stratovolcano
Composite Cones - Stratovolcano Most encircle the pacific
ocean (ring of fire) as part of magmatic arcs
Large – ~1 km high, 5 - 25 km wide
Symmetrical structure Composed of alternating
lava flows and pyroclastic deposits
Product of high viscosity magma
Have violent eruptions
Mount Rainer
Plate Tectonics and Igneous RocksPlate Tectonics and Igneous Rocks
Fig. 6.6
Hot SpotsHot Spots
Produced by rising plume of mantle material (mantle plume)
They are stationary – plates move over the hotspots
Basalts produced by hot spots are chemically different from basalts produced at MOR
Hot Spot Example – Island ChainsHot Spot Example – Island Chains
Island Chain FormationIsland Chain Formation
Hot Spot Under HawaiiHot Spot Under Hawaii
Notice linear layout of islands
Could determine plate movement rate for data
Island continually being formed
Shield VolcanoesShield Volcanoes
Broad, slightly domed strucutre Large structure 9 km (~6 miles) high & 50 km
(~30 miles) wide Produced by fluid (low viscosity) lava Example: Mauna Loa, Kilauea, other island
chains
Shield VolcanoesShield Volcanoes
Volcano Size ComparisonVolcano Size Comparison
Hot Spot Example – ContinentalHot Spot Example – Continental
Yellowstone
Continental Hot Spot MechanicsContinental Hot Spot Mechanics
Volcanism and Continental Hot SpotsVolcanism and Continental Hot Spots