No Quiz This Week

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No Quiz This Week

• Exam tomorrow night here, 7 PM
• Bring a pen/pencil you can write a short essay
  with
• Extra credit (up to 5 extra)- redo the exam with
  discussion in small groups (800)

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So Far, Weve Covered...

• Basic Earth Properties and Maps
• Ocean Basin Features
• Plate Tectonics

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Whats Next?

• Sediments
• Ocean Water Physical Properties
• Density, Evaporation
• Ocean Water Chemical Properties
• Dissolved matter
• Salinity
• Nutrients

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Class 11

• OCEAN SEDIMENTS
• Introduction
• Marine sedimentary provinces
• Importance of particle size
• Terrigenous sediments
• Turbidity currents

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"The sediments are a sort of epic poem of the
Earth." -Rachel Carson
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Ocean sediments are our best record of Earth
history!
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Ocean sediments are somewhat like a book of earth
history- every detail says something about events
on the earth. Many sedimentary rocks can be
found on land today.
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Sedimentation Patterns

• Layering -- oldest at bottom, youngest at top
• How thick are they?
• very little on mid-ocean ridges
• up to 10,000 m beneath continental rises
• average 500 m
• Sediments collect slowly
• Deep ocean (avg.) 0.5 - 1.0 cm/1000 yr
• Continental margins 10 - 50 cm/1000 yr
• River mouths may be higher

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• Where does all this stuff come from?
• Continents (weathering and erosion)
• Biogenic particles
• Volcanic ash
• Chemical precipitates
• Micro-meteorites
• Why do we care?
• Oil, gas, and other resources
• Record of past conditions and processes

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Neritic
Pelagic
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Marine Sediment Provinces
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Sediment Types (Table 4.1)
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Coarse
Finer
Finest
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Particles Sizes in Sediment- Interpretation

• (1) Larger --gt sink faster
• (2) Faster-moving water holds coarser sediment
  and more of it.
• (3) Rapid currents transport coarse fine seds.
  
• (4) Slow currents transport only fine sediments.
• So.
• Coarsest Particles beaches, near-shore, inner
  shelf -- "fast" currents
• Finest quieter places

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Sediment Types (Table 4-1)
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LITHOGENOUS SEDIMENTS

• (1) Terrigenous sediment
• 75 of all marine sediment (by mass)
• Mostly settles on continental margins
• So they DO NOT cover a very large area
• Atlantic Large fans spread out on the
  deep-sea floor
• Pacific Ocean Trapped by trenches little
  transported to deep-sea floor

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Erosion removes material from land Where does
it go?
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Turbidity Currents Move sediment down the
continental margins
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Turbidity Currents

• Dense, muddy water (turbid water) cloud or slurry
  that flows down the continental slope onto the
  continental rise- HUGE

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• Turbidity current dense slurry (avalanche) of
  poorly sorted, suspended sediment
• Sediment deposited as current slows
• Largest particles settle first (poorly sorted)
• Finer particles settle next
• Finest particles (mud) settle last

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Turbidity Currents http//faculty.gg.uwyo.edu/hel
ler/sed_video_downloads.htm
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LITHOGENOUS SEDIMENT- Pelagic

• (2) "Red Clay" -- terrigenous dust volcanic ash
• Transported to open ocean by winds water
  currents
• Settles eventually
• Dominant only in deep areas where other types
  absent.

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