This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Rocks, Sediment and SoilsProducts of an Active PlanetEarth’s structure leads to intense geologic activity Inner core: Solid iron Outer core: Liquid iron,
Crust (Lithosphere): Rigid, thin O, Si, Al, Fe, Ca, Na, K, Mg…
Crust: Rigid, Thin
Mantle: Plastic, Convecting
47%, 28, 8, 5, 4, 3, 3, 2 TDE pg.8-11
The Major Lithospheric Plates And directions of movement (TDE pg.5)
Divergent Plate Boundaries: where plates move away from each other new oceanic crust is generated from melting mantle material that cools and forms Basaltic Rock (a.k.a. Mafic rock) Iron-rich Silicon-poor Dense Young
TDE pg.15-20, 32-36
Geologic Phenomena at Plate Boundaries
Asthenosphere
Lithosphere LithosphereSimplified Block Diagram
New Oceanic CrustForming at Mid-Ocean Ridge
Oceanic Crust
Lithospheric Plate MovementMagma
Generation
Geologic Phenomena at Divergent Plate Boundaries
Divergent Plate Boundary
Lithosphere
Asthenosphere Welling up of hot mantle rock (solid but soft)
Fissure Eruptions
Shallow Earthquakes
Locations of Divergent Plate BoundariesMid-Ocean Ridges East Pacific Rise Mid Atlantic Ridge Mid Indian Ridge Mid Arctic Ridge
(Mid-Arctic Ridge)
Eas
t Pac
ific
Ris
e
Mid
-Atla
ntic
Rid
ge
Indian
Ridge
Mid-
Divergent Plate Boundaries and Hotspots Beneath Continents
The Rocks (igneous) Basalt bedrock is usually formed in the shallow crust by
recent (<~200mya) volcanic activity at divergent plate boundaries or hotspots (>1,000oC)
E.g., volcanoes, feeder dikes, volcanic stocks, basalt floods Hawaii, Ship Rock NM, Devils Tower AZ, Yellowstone WY
Shallow earthquake activityVolcanic activity
Fissures eruptions Lava floods, and volcanoes Hot, non-explosive Basaltic rocks formed (i.e.
iron-rich/silica poor)
Flood Basalts on Uplift
Fig. 19.21 Fig. 19.22
Rift Valley
Passive continental shelf and rise
Rift Valley
E.g., Red Sea and East African Rift Valleys
Thinning crust, flood basalts, long lakes
ShallowEarthquakes
Linear sea, uplifted and faulted margins
Oceanic Crust
Mafic Magmas Hot (>1000oC) Non-Viscous (runny, flows easily) “Dry” (no H2O or C02)
Mafic Rocks Usually Extrusive, Fine-grained, Mafic (Basalt) rock forms oceanic
crust, Shield Volcanoes and Flood Basalts
If Intrusive, course-grained mafic rocks are formed Gabbro.
If intrusive, Dikes and Sills more common. (Plutons don’t form)
Formation of Mafic Igneous Rocks
DikeDike
Dike
Sill
Sill Sill
Geologic Phenomena at Plate Boundaries
Convergent Plate Boundaries: where plates move toward each other, oceanic crust and the underlying lithosphere is subducted beneath the other plate (with either oceanic crust or continental crust)