Sediment Types in Oceanography
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Questions and Answers

Where are terrigenous sediments typically seen on the globe?

on continental margins

What is the source of terrigenous sediments?

erosion of land, volcanic eruptions, and blown dust

Give examples of terrigenous sediments.

Quartz sand, clays, and estuarine mud

Other than continental margins, where do you see terrigenous sediments?

<p>abyssal plains and polar ocean floors</p> Signup and view all the answers

What is biogenous sediment?

<p>sediment of biological origin; organisms can deposit calcareous or siliceous residue</p> Signup and view all the answers

What is the source of biogenous sediment?

<p>organic: accumulation of hard parts of some marine organisms</p> Signup and view all the answers

Give examples of biogenous sediment.

<p>calcareous and siliceous oozes</p> Signup and view all the answers

Where are biogenous sediments distributed?

<p>dominant over deep-ocean floor</p> Signup and view all the answers

Where do you find siliceous ooze dominating?

<p>below about 5 km</p> Signup and view all the answers

What is hydrogenous sediment?

<p>a sediment formed directly by precipitation of dissolved minerals from seawater</p> Signup and view all the answers

Hydrogenous sediment is also called ___

<p>authigenic sediment</p> Signup and view all the answers

What is the common source of hydrogenous sediment?

<p>bacteria</p> Signup and view all the answers

Give examples of hydrogenous sediments.

<p>manganese nodules and phosphorite deposits</p> Signup and view all the answers

What is the distribution of hydrogenous sediments?

<p>present with other, more dominant sediments</p> Signup and view all the answers

What are cosmogenous sediments?

<p>sediment of extraterrestrial origin</p> Signup and view all the answers

Give examples of cosmogenous sediments.

<p>tektite spheres and glassy nodules</p> Signup and view all the answers

What type of sediment is the least abundant?

<p>cosmogenous sediments</p> Signup and view all the answers

What are the two major sources of cosmogenous sediments?

<ol> <li>interplanetary dust that falls constantly into the top of the atmosphere 2) rare impacts by large asteroids and comets</li> </ol> Signup and view all the answers

What is the distribution of cosmogenous sediments?

<p>typically in very small proportions (&lt; few ppm) mixed with more dominant sediments</p> Signup and view all the answers

Occasionally, cosmogenous sediment includes _____

<p>microtektites</p> Signup and view all the answers

Microtektites:

<p>translucent, oblong particles of glass; thought to form from violent impact of large meteors or small asteroids on Earth's crust</p> Signup and view all the answers

Where might you see manganese nodules (representative of hydrogenous sediments)?

<p>along deep seabeds</p> Signup and view all the answers

Where might you see phosphorite nodules (representative of hydrogenous sediments)?

<p>along some continental margins</p> Signup and view all the answers

Hydrogenous sediments usually accumulate ______

<p>very slowly</p> Signup and view all the answers

When might you see rapid deposition of hydrogenous sediment?

<p>in rapidly drying lakes</p> Signup and view all the answers

What is the second-most abundant marine sediment?

<p>biogenous</p> Signup and view all the answers

Most organisms that produce biogenous sediments _____

<p>drift free in the water as plankton</p> Signup and view all the answers

Biogenous sediments are most abundant where ___, such as ____

<ol> <li>ample nutrients encourage biological productivity 2) continental margins or areas of upwelling</li> </ol> Signup and view all the answers

Which covers a larger area of the ocean floor: terrigenous or biogenous sediments?

<p>biogenous</p> Signup and view all the answers

Which sediments dominate in total volume?

<p>terrigenous</p> Signup and view all the answers

What is the source of the quartz and clay that makes up terrigenous sediments?

<p>granite</p> Signup and view all the answers

What are the two most common components of terrigenous marine sediments?

<p>quartz and clay</p> Signup and view all the answers

Describe quartz.

<p>a hard, relatively insoluble, very durable mineral that can withstand extensive weathering and transport</p> Signup and view all the answers

____ sands washed from adjacent land are important components of the sediments along continental margins.

<p>quartz</p> Signup and view all the answers

What is feldspar?

<p>an important material in granite that ultimately combines with carbonic acid and seawater to form clay</p> Signup and view all the answers

What is the chief component of soils?

<p>clay</p> Signup and view all the answers

How is clay carried to the ocean?

<p>by wind, rivers or streams</p> Signup and view all the answers

Clays will settle _______

<p>to the deep-ocean floor</p> Signup and view all the answers

What percentage of all ocean floor area do terrigenous sediments cover?

<p>about 45%</p> Signup and view all the answers

What percentage of all ocean floor area do biogenous sediments cover?

<p>about 55%</p> Signup and view all the answers

What percentage of all ocean floor area do hydrogenous sediments cover?

<p>&lt; 1%</p> Signup and view all the answers

What percentage of all ocean floor area does cosmogenous sediments cover?

<p>0%</p> Signup and view all the answers

Terrigenous sediments are delivered by ___

<ol> <li>rivers 2) coastal erosion 3) wind (as dust) 4) volcanoes 5) glaciers 6) icebergs</li> </ol> Signup and view all the answers

Describe the cycle involving terrigenous sediments.

<p>Mountains rise as plates collide, fuse and subduct. The mountains erode, and sediments are transported to sea via wind and water. Sediments collect on sea floor, and travel with the plate. They are either uplifted or subducted, and made into mountains where the cycle begins again.</p> Signup and view all the answers

What is the main source of terrigenous sediments?

<p>rivers</p> Signup and view all the answers

Clays are more likely to be found ___ in the oceans.

<p>in the abyssal zone (deep ocean basin)</p> Signup and view all the answers

Globally, where do you see a large portion of siliceous ooze?

<p>along northern coast of Antarctica</p> Signup and view all the answers

Most sediment deposits are composed of ___

<p>a mixture of biogenous and terrigenous particles, with an occasional hydrogenous or cosmogenous supplement</p> Signup and view all the answers

How are neritic sediments different from the deeper basin floor sediments?

<p>Neritic sediments consist primarily of terrigenous material, contain coarser sediments, and lower proportion of biogenous sediment. Deep-ocean floors are covered by finer sediments and have a greater proportion of biogenous sediment.</p> Signup and view all the answers

Pelagic sediments:

<p>sediments of the slope, rise and deep-ocean floor that originate in the ocean</p> Signup and view all the answers

What constitutes gravel?

<p>boulder, cobble, pebble, granule</p> Signup and view all the answers

What does compaction of gravel create?

<p>conglomerates</p> Signup and view all the answers

What constitutes sand?

<p>very coarse sand, medium sand, fine sand, and very fine sand</p> Signup and view all the answers

What does compaction of sand create?

<p>sandstone</p> Signup and view all the answers

What is silt composed of?

<p>silt</p> Signup and view all the answers

What does compaction of silt create?

<p>siltstone</p> Signup and view all the answers

What is clay composed of?

<p>clay</p> Signup and view all the answers

What does compaction of clay create?

<p>mudstone</p> Signup and view all the answers

Mudstone is also called __

<p>shale</p> Signup and view all the answers

What is the order of grain diameter between marine sediments (smallest to largest)?

<p>clay &lt; silt &lt; sand &lt; gravel &lt; boulders</p> Signup and view all the answers

What is the only thing with a grain diameter as large as boulders?

<p>whale earbones</p> Signup and view all the answers

Mud grain diameter lies between those of ____ and ____

<p>clay and silt</p> Signup and view all the answers

Glacial sediment grain diameter is very broad.

<p>True</p> Signup and view all the answers

What is the basis of sediment classification?

<p>size and origin</p> Signup and view all the answers

____ is a strong function of sediment size.

<p>sediment mobility (e.g. settling velocity)</p> Signup and view all the answers

Sediment is sorted into ____

<p>different sizes</p> Signup and view all the answers

How long does it take for sand to settle 4 km deep?

<p>1.8 days</p> Signup and view all the answers

How long does it take for silt to settle 4 km deep?

<p>6 months</p> Signup and view all the answers

How long does it take for clay to settle 4 km deep?

<p>50 years</p> Signup and view all the answers

How long will granules take to settle 4 km deep?

<p>NA</p> Signup and view all the answers

How long will pebbles take to settle 4 km deep?

<p>NA</p> Signup and view all the answers

How long will cobbles take to settle 4 km deep?

<p>NA</p> Signup and view all the answers

What are the primary effects on the type of terrigenous sediments that end up in the oceans?

<ol> <li>elevation of source region 2) weathering 3) types of materials transported 4) reworking</li> </ol> Signup and view all the answers

How does elevation of source region affect types of terrigenous sediments in the ocean?

<p>The higher the elevation, the higher the energy thus the increased ability to carry sediments to the ocean</p> Signup and view all the answers

How does elevation change as you enter the ocean?

<p>goes from high to low - causes smaller particles to be carried furthest</p> Signup and view all the answers

The higher the elevation of a source region, the higher the potential for ____

<p>erosion and thus deposition</p> Signup and view all the answers

How does weathering affect terrigenous sediments in the ocean?

<p>Increased weathering of sediments on land (via precipitation) will increase erosion and runoff, increasing transport of sediment to oceans via rivers and streams</p> Signup and view all the answers

Which latitudes would you expect lots of weathering to happen, and thus more terrigenous sedimentation deposition in oceans?

<p>tropical</p> Signup and view all the answers

Why is the highest precipitation weather regime not exactly at the equator?

<p>because of shift in intertropical convergent zone northwards</p> Signup and view all the answers

When will precipitation dominate an environment?

<p>when the precipitation is greater than evaporation</p> Signup and view all the answers

Which latitude regions have precipitation greater than evaporation?

<p>around equator, and between 40 and 60 degrees</p> Signup and view all the answers

Which latitude regions have evaporation greater than precipitation?

<p>between 15 and 40 degrees and above 70 degrees</p> Signup and view all the answers

The majority of weathering is chemical.

<p>False</p> Signup and view all the answers

The amount of mechanical weathering is highest in ____ areas that are _____

<p>tropical areas that are at a very high elevation</p> Signup and view all the answers

As you go from areas of high relief to plains, mechanical weathering ____

<p>decreases</p> Signup and view all the answers

As you go from tropical to arctic, which areas have the highest weathering?

<p>tropical, subtropical, and humid temperate areas</p> Signup and view all the answers

Which areas have absolutely zero chemical weathering?

<p>lowlands with inland ice, and mountain ranges (i.e. glaciated areas)</p> Signup and view all the answers

How many types of sandstones are there?

<p>4</p> Signup and view all the answers

What are some different types of materials being transported?

<p>mudstone, sandstones, massive conglomerates, debris, bedded conglomerate, and volcanic ash</p> Signup and view all the answers

What is tuff?

<p>volcanic ash</p> Signup and view all the answers

What types of sandstones are there?

<ol> <li>overbank 2) pebbly 3) Bedded 4) trough and planar cross-bedded</li> </ol> Signup and view all the answers

What type of material would you expect to be transported the shortest distance from its source?

<p>bedded conglomerate (Sheet floods)</p> Signup and view all the answers

What river discharges the most sediment per year, globally?

<p>Hwang Ho (Asia); discharges 2100 million tonnes/year</p> Signup and view all the answers

Which rivers in North America discharge some of the most sediment globally?

<p>Mississippi (#7) and Colorado (#10)</p> Signup and view all the answers

Where would you expect the most runoff to the Pacific Ocean to come from (top 2)?

<ol> <li>Hwang Ho River 2) Yangtze River</li> </ol> Signup and view all the answers

Where would you expect the most runoff into the Indian Ocean to come from?

<ol> <li>Ganges River 2) Brahmaputra River 3) Indus River</li> </ol> Signup and view all the answers

Where would you expect most of the glacial sources of sediment to come from?

<p>Antarctica, Greenland and Canadian Arctic</p> Signup and view all the answers

Where is the largest sediment discharge into the Atlantic Ocean to come from?

<p>Amazon</p> Signup and view all the answers

Where is the second largest sediment discharge river into the Atlantic?

<p>Mississippi</p> Signup and view all the answers

Where does the Colorado dump its sediment?

<p>Pacific Ocean</p> Signup and view all the answers

Study Notes

Terrigenous Sediments

  • Found primarily on continental margins.
  • Source includes erosion of land, volcanic eruptions, and blown dust.
  • Examples include quartz sand, clays, and estuarine mud.
  • Also present in abyssal plains and polar ocean floors.

Biogenous Sediments

  • Composed of biological origin material; organisms deposit calcareous or siliceous residues.
  • Source is organic, originating from hard parts of marine organisms.
  • Examples include calcareous and siliceous oozes.
  • Dominant over deep-ocean floor distributions.

Hydrogenous Sediments

  • Formed by precipitation of dissolved minerals from seawater; also known as authigenic sediment.
  • Commonly sourced from bacteria.
  • Examples are manganese nodules and phosphorite deposits.
  • Found mixed with more dominant sediments and accumulate slowly.

Cosmogenous Sediments

  • Of extraterrestrial origin; least abundant sediment type.
  • Examples include tektite spheres and glassy nodules.
  • Two main sources are interplanetary dust and impacts from large asteroids or comets.
  • Typically present in very small proportions (< few ppm) mixed with other sediments.

Microtektites

  • Translucent, oblong glass particles formed from meteor impacts.

Sediment Distribution and Composition

  • Terrigenous sediments cover about 45% of ocean floor area; biogenous sediments cover about 55%.
  • Hydrogenous sediments cover less than 1%, while cosmogenous sediments are negligible (< 0%).
  • Terrigenous sediments are delivered by rivers, coastal erosion, wind, volcanoes, glaciers, and icebergs.

Sedimentation Processes

  • The sedimentation cycle involves the erosion of mountains, transport via rivers, and eventual deposition on ocean floors.
  • The primary source of terrigenous sediments is rivers.
  • Clays are more prevalent in the abyssal zone, while siliceous ooze is found along the northern coast of Antarctica.

Sediment Types and Compaction

  • Gravel (boulders, cobbles, pebbles, granules) compacts to form conglomerates.
  • Sand (varying sizes) compacts to form sandstone.
  • Silt compacts into siltstone, and clay compacts into mudstone (also known as shale).

Grain Size and Sediment Mobility

  • Order of sediment grain diameter from smallest to largest: clay < silt < sand < gravel < boulders.
  • Mechanical weathering is the most common form of weathering; highest in tropical, elevated areas.
  • Sediment is classified based on size and origin, influencing sediment mobility.

Weathering and Erosion

  • Weathering, especially mechanical, increases sediment transport to oceans.
  • Tropical regions have greater terrigenous sedimentation due to higher precipitation.
  • Precipitation must exceed evaporation for major sediment deposition, particularly around the equator and between 40-60 degrees latitude.

Major Rivers Discharging Sediment

  • The Hwang Ho (Yellow River) discharges the most sediment globally, approximately 2100 million tonnes/year.
  • In North America, the Mississippi and Colorado Rivers are significant sediment contributors.
  • The Amazon is the largest sediment discharger into the Atlantic Ocean; the Ganges, Brahmaputra, and Indus rivers discharge into the Indian Ocean.

Glacial Sources

  • Major glacial sediments come from Antarctica, Greenland, and the Canadian Arctic.

Summary

  • Most sediment deposits consist of a mixture of biogenous and terrigenous particles, with occasional contributions from hydrogenous or cosmogenous sources.

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Description

Explore the different types of sediments found in oceans, including terrigenous, biogenous, hydrogenous, and cosmogenous sediments. This quiz covers their origins, examples, and distributions across various oceanic environments. Test your knowledge on how these sediments contribute to marine geology.

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