Transcript METAMORPHISM & METAMORPHIC ROCKS

The Sea Floor
Origin of the Ocean
• Water vapor released during
degassing of early earth
–volcanism
• Salt from chemical
weathering
Methods of Studying the Sea
Floor
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Rock Dredge
Corer
Sea-Floor Drilling
Submersibles
Echo Sounder
• Seismic Profiler
• Surveys - Magnetic, Gravity, Seismic
Refraction
• Deep Sea Cameras
Features of the Sea Floor
• Continental Margins
– Passive
– Active
• Oceanic trench
• Mid-oceanic ridge
• Seamounts
Continental Shelves and
Continental Slopes
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Vertical exaggeration in diagrams
Continental shelf
Continental slope
Continental rise
Active Continental Margins
• On land- earthquakes, young mountain belt,
volcanoes
• Continental shelf, continental slope, oceanic
trench
• Oceanic Trenches
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Earthquakes of the Benioff seismic Zones
Volcanoes
Low Heat Flow
Negative Gravity Anomalies
Submarine Canyons
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Abyssal Fans
Bottom Currents
Down-canyon movement of sand
Bottom currents
River erosion
Turbidity Currents
– Graded bedding
– Shallow water fossils
Passive Continental Margins
• Continental shelf, slope, rise
• The Continental Rise
– Types of Deposition
• From turbidity currents
• From contour currents
• Abyssal plains
Fracture Zones
• Offset rift valleys
• Transform Fault
– Portion that has earthquakes
Seamounts, Guyots, and
Aseismic Ridges
• Seamounts
• Guyots
• Aseismic ridges
Reefs
• Fringing Reefs
• Barrier Reefs
• Atolls
Sediments of the Sea Floor
• Terrigenous Sediment
• Pelagic Sediment
– thickness increases away from crest of midoceanic ridge
Deep-sea sediments, those found at
depths greater than about 500 m,
cover roughly two-thirds of the Earth.
The predominant deep sediment is
carbonate ooze, which covers nearly
half the ocean floor
The Mid-Oceanic Ridge
• Rift Valley
• Geologic Activity on the Ridge
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Shallow-focus Earthquakes
High Heat Flow
Basalt Eruptions
Hot springs
• Black Smokers
• Biologic Activity on the Ridge
– Geomicrobiology
Oceanic Crust and Ophiolites
• Evidence for composition of the oceanic
crust
• Ophiolite (from top to bottom)
– Marine sedimentary rock
– Pillow basalt
– Sheeted dike complex
– Gabbroic intrusions
– Ultramafic rock
The Age of the Sea Floor
• Younger than 200 million years old
• Parts of continents much older