Oceanography: Chapter 4 (Marine Sediments)

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What do marine sediments consist of?
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Eroded particles and fragments of dirt, dust and other debris.
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Marine sediments have been used to study what?
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Past climate, geology, and biology.
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What do sediments over time turn into?
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Rock – found in the world’s tallest mountains.
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What do marine sediments provide?
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A variety of important resources.
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What is the study of how ocean, atmosphere, and land interactions have produced changes in ocean chemistry, circulation, biology, and climate.
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Paleoceanography.
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What five pieces of evidence provide clues of our Earth’s history?
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1. Marine organism distribution 2. Ocean floor movements 3. Ocean circulation 4. Climate change 5. Global extinction
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Where would we find clues to the origin of sediments?
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Mineral composition and texture (size and shape).
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Lithogenous
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Derived from land (small particles eroded from land; also called terrigenous; produced by weathering.
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Biogenous
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Derived from organisms.
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Hydrogenous (Authigenic)
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Derived from water.
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Cosmogenous
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Derived from outer space.
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What are the two modern explorations of the ocean?
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Cores and Rotary Drilling.
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Define Cores
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Hollow steel tubes collect sediment columns.
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Define Rotary Drilling
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Collects deep ocean sediment cores.
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How are Lithogenous sediments carried to the ocean?
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Streams, wind, glaciers, and gravity.
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Where is the greatest quantity of Lithogenous material found?
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Around continental margins.
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Where are you more likely to find coarse lithogenous sediments as opposed to fine lithogenous sediments?
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Coarser sediments are closer to shore and finer are father away.
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What is the main ingredient in lithogenous sediments?
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Mainly mineral quartz (SiO2).
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How is grain size classified?
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Wentworth scale of grain size.
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What is one of the most important sediment properties?
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Grain size.
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What are the four types of Neritic Lithogenous Sediments?
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1. Beach Deposits 2. Continental Shelf 3. Turbidite Deposits 4. Glacial Deposits
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What do beach deposits consist of?
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Mainly wave-deposited quart-rich sands.
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What does the continental shelf consist of?
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Relict sediment, covering 70% of the world’s continental shelf.
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What are turbidite deposits?
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Underwater avalanches; forms submarine canyons; spreads to form “fans”; consists of graded bedding.
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What are glacial deposits?
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Located in high latitude environments (currently forming by ice rafting).
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What are Pelagic Deposits?
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Fine grained material that accumulates slowly on deep ocean floors.
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Pelagic lithogenous sediments comes from what three things?
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1. Volcanic ash (eruptions) 2. Wind blown dust 3. Fine grained material transported by deep ocean currents
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Why is abyssal clay red?
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Oxidized Iron (FE).
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When is abyssal clay most likely to be abundant?
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When other sediments are absent.
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What are abyssal clays composed of?
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At least 70%, fine, clay sized particles from the continents.
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What do biogenous materials (ooze) consist of?
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30% skeletal debris, 70% inorganic mud particles.
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Macroscopic
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Visible to the naked eye (teeth, bones, shells).
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Microscopic
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Seen under a microscope (tiny shells)
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Biogenous deposits consist of what two Oozes?
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Calcareous Oozes (Calcium Carbonate) and Siliceous Oozes (Silica)
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Calcareous oozes break down into what two divisions?
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Foraminifers (animal) and Coccolithophores (plant)
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Siliceous Oozes break down into what two divisions?
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Radiolarians (animal) and Diatoms (plant)
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Coccolithophores (animal)
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Range small to large; ingest organisms for food.
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Foraminifers (plant)
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microscopic algae; photosynthesize; spherical shell; forms chalk when dies.
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Radiolarians (animal)
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glass-like exoskeleton; wide variety of patterns; gathers food through pores.
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Diatoms
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Photosynthesize; require strong sun; nutrients allowed in through pores, and waste out; used in many products.
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Distribution of sediments depends on what three processes?
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1. Productivity 2. Destruction 3. Dilution
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Where are Neritic deposits found?
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Shallow water.
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Where are Pelagic deposits found?
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Deep water.
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What is CCD?
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Calcite Compensation Depth is the point at which all calcite dissolves.
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What happens to Calcareous oozes in deep water (Pelagic Deposits)?
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Destruction varies with depth and temperature of water; depth speeds dissolution; CCD is reached
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What happens to Silicious oozes in deep water (Pelagic Deposits)?
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Silica dissolves slowly at all depths; limited amounts of silica; accumulation in high productivity zones.
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A change in these two conditions allows for precipitation.
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Temperature and pressure
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What four types of minerals precipitate directly from sea water?
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1. Manganese Nodules 2. Phosphates 3. Carbonates 4. Metal sulphides
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Where are phosphates economically useful?
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Fertilizers.
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What are metal sulphides associated with?
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Hydrothermal vents and black smokers.
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Where are hydrothermal vents and black smokers found?
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Along the mid-ocean ridge.
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Metal sulphide deposites contain what 6 things?
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1. Iron 2. Nickel 3. Copper 4. Zinc 5. Silver 6. Other materials
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How are metal sulphide deposits transported?
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Sea floor spreading.
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What are Evaporates?
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minerals that form when sea water evaporates.
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What two minerals are considered evaporates?
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Halite (table salt) and Gypsum
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How is cosmogenous sediment produced?
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From materials originating in outer space
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Where are distributions of Neritic and Pelagic deposits controlled?
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1. Proximity to sources of lithogenous sediments 2. Productivity of microscopic marine organisms 3. Depth of water 4. Sea floor features
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Neritic sediments cover approximately how much of the sea floor?
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1/4
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Pelagic sediments cover approximately how much of the sea floor?
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3/4
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Macroscopic sherules
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