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Earth’s Layers Four distinct layers Inner Core (1,228 km radius) Hottest High density solid nickel and iron Outer Core (2,260 km thick) Hot Molten nickel and iron Mantle (2,890 km thick) Less dense than inner and outer cores Molten silicates Crust (8-12 km thick) solid
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Oceanography Unit 2 Earths Layers Four distinct layers Inner
Core (1,228 km radius)
Hottest High density solid nickel and iron Outer Core (2,260 km
thick) Hot Molten nickel and iron Mantle (2,890 km thick) Less
dense than inner and outer cores Molten silicates Crust (8-12 km
thick) solid Crust Mantle Outer Core Inner Core Page 55 Earths
crust floats
Lithosphere strong, rigid behavior Consists of crust and the upper
mantle material fused together Asthenosphere weak, ductile behavior
Low velocity plastic layer (molten magma) Earths Crust Oceanic
Crust (Basalt) Continental Crust (Granitic)
Lots of silica and iron More dense than continental crust Always
subducts under continental Not much more than 7 km thick generally
Continental Crust (Granitic) Lots of silica and aluminum A few km
(edge of continents) to over 32 km (middle of continents) 12 Major
Plates Mountain Mover, Earth Shaker Oceanic Ridges/Rises Divergent
oceanic plate boundary
Undersea mountain ranges Rift Valley where volcanism occurs and new
crust is created Mid-Atlantic Ridge 2.2 inches/year East Pacific
Rise 12.6 inches/year video Deep Sea Trenches Subduction Zones
Plate Convergence
May be twice as deep (almost 12,000 m) as the regular deep-sea
floor (up to 6,000 m) Excess crust subducted and melted Earthquake
activity Hydrothermal Vents Seafloor outlet for high-temperature
water and associated mineral deposits (a hot spring) High interest
area of study video Brine Shrimp Life Cycle Ocean Soundings Our
ability to accurately map the features of the sea floor has been
acquired only recently and continues to improve with advancing
technology. Early soundings included: Rocks tied to ropes
Cannonballs and piano wire Now: Echo soundings consistent speed of
sound in seawater and accurate time measurements Continental Margin
Consists of shelf, shelf break, slope, and rise Passive vs. Active
Passive continental margins:
found around the rim of the Atlantic Ocean are not plate boundaries
have little or no seismic or volcanic activity form when a
continent rifts apart creating a new ocean basin between the
fragments. Active continental margins: are found around the rim of
the Pacific Ocean are plate boundaries are typically seismically
and/or volcanically active tend to be relatively narrow Continental
Margin Continental Shelf
very flat edges of the continental crust covered by marine waters
Narrow shelves associated with steep slopes Wider shelves
associated with relatively flat continental regions Seafloor
Features Submarine Canyons Deep v-shape
Cut across continental margins Some can be traced from river
systems Abyssal Plain Flat ocean basin floor Extends seaward from
continental slope and rise Seafloor Features Abyssal hills Less
than 1000 m high Seamounts
Greater than 1000 m high Guyots Flat-topped seamounts Islands
Seamounts that rise above the sea surface Coral Reefs Often built
on islands and seamounts Fringing Reef
Attached directly to the shore of an island or continent Barrier
Reef Parallels land but is some distance offshore with water
between Atoll Ring-shaped coral reef that encloses a lagoon