pakistan earthquake – 7.6 m agnitude october 8, 2005 (8:50 p.m. local time)
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Pakistan EarthquakePakistan Earthquake – – 7.6 M7.6 MagnitudeagnitudeOctober 8, 2005 (8:50 p.m. local time)
Ocean SedimentsOcean Sediments
Origin and DistributionOrigin and Distribution
Marine SedimentsMarine Sediments
• Most ocean floor covered by marine sedimentsMost ocean floor covered by marine sediments• Sediment thickness is thinnest at mid-ocean ridge and Sediment thickness is thinnest at mid-ocean ridge and
thickest at continental marginsthickest at continental margins
Types of Ocean Sediments
• Terrigenous – “rock-derived”Terrigenous – “rock-derived”
• Biogenous – “life-derived”Biogenous – “life-derived”
• Cosmogenous – “cosmic-derived”Cosmogenous – “cosmic-derived”
• Hydrogenous – “water-derived”Hydrogenous – “water-derived”
Sediment Distribution - Sediment Distribution - LithogenousLithogenous
LithogenousLithogenous SedimentsSediments
• Composed mostly of quartz sand and clayComposed mostly of quartz sand and clay
• Derived from the weathering of rocks – continents or Derived from the weathering of rocks – continents or volcanic islandsvolcanic islands
• Most deposited on continental marginsMost deposited on continental margins• Transported by rivers, glaciers or windTransported by rivers, glaciers or wind
• Covers about 45% of ocean floorCovers about 45% of ocean floor
Lithogenous Sediment - Lithogenous Sediment - ExamplesExamples
• Red ClaysRed Clays– Terrigenous from rivers, dust, and Terrigenous from rivers, dust, and
volcanic ashvolcanic ash
– Transported to deep ocean by winds Transported to deep ocean by winds and surface currentsand surface currents
– Common in deep oceansCommon in deep oceans
– Accumulates 2 mm (1/8”) every 1,000 yearsAccumulates 2 mm (1/8”) every 1,000 years
Mt. Pinatubo Mississippi River Sahara Desert
Sediment Distribution - Sediment Distribution - BiogenousBiogenous
• Calcareous and Siliceous OozesCalcareous and Siliceous Oozes
Biogenous SedimentBiogenous Sediment
• Biogenic ooze – greater than 30% biogenous sedimentBiogenic ooze – greater than 30% biogenous sediment
• Composed mostly of hard skeletal parts of once-living Composed mostly of hard skeletal parts of once-living organismsorganisms
• Two main compositions of hard parts:Two main compositions of hard parts:
1.1. Calcium Carbonate (CaCOCalcium Carbonate (CaCO33))a)a)Coccolithophore (phytoplankton)Coccolithophore (phytoplankton)b)b)Foraminifera (zooplankton)Foraminifera (zooplankton)
2. Silica (SiO2. Silica (SiO22) ) a) Diatoms (phytoplankton)a) Diatoms (phytoplankton) b) Radiolarian (zooplankton)b) Radiolarian (zooplankton)
Biogenous – Calcareous ExamplesBiogenous – Calcareous Examples
• Composed of CaCOComposed of CaCO33
• Widespread in Widespread in relatively shallow relatively shallow areasareas Coccolithophore
Foraminifera
Foraminifera
Biogenous – Biogenous – Siliceous ExamplesSiliceous Examples
Diatoms
Radiolarians
• Composed of SiOComposed of SiO22
• Base of food chainBase of food chain
Sediment DistributionSediment Distribution – – Calcareous/SiliceousCalcareous/Siliceous
Biogenous – Biogenous – Calcareous oozesCalcareous oozes• Cover greater than 50% of ocean floorCover greater than 50% of ocean floor
• Distribution controlled by dissolution processesDistribution controlled by dissolution processes
• Cold bottom waters undersaturated with respect to CaCOCold bottom waters undersaturated with respect to CaCO33
– slightly acidic ( COslightly acidic ( CO22))– readily dissolves CaCOreadily dissolves CaCO33
• Calcium Carbonate Compensation Depth (CCD)Calcium Carbonate Compensation Depth (CCD) – the depth at – the depth at which the rate of accumulation of calcareous sediments which the rate of accumulation of calcareous sediments equals the rate of dissolutionequals the rate of dissolution
• Pacific Ocean – 500-1,500 mPacific Ocean – 500-1,500 m • Atlantic Ocean – 4,000 mAtlantic Ocean – 4,000 m
CaCOCaCO33 is found is found
Biogenous – Siliceous OozeBiogenous – Siliceous Ooze
• Covers 15% of ocean floorCovers 15% of ocean floor
• Diatoms common at higher latitudesDiatoms common at higher latitudes• Radiolarians common at equatorial regionsRadiolarians common at equatorial regions
• Distribution - areas of high productivity (zones of upwelling)Distribution - areas of high productivity (zones of upwelling)• Dissolve more slowly than calcareous particlesDissolve more slowly than calcareous particles
Siliceous OozesSiliceous Oozes
Sediment Distribution - Sediment Distribution - HydrogenousHydrogenous
Hydrogenous SedimentsHydrogenous Sediments
• Produced by chemical processes in seawaterProduced by chemical processes in seawater• Sediment precipitates from waterSediment precipitates from water
• OolitesOolites – occur in surface waters supersaturated in CaCO – occur in surface waters supersaturated in CaCO33
• Manganese NodulesManganese Nodules – manganese, iron deposits – manganese, iron deposits accumulate in areas of low sedimentationaccumulate in areas of low sedimentation
• EvaporitesEvaporites – “salt precipitates” form in areas of high – “salt precipitates” form in areas of high evaporationevaporation
• Some Examples:Some Examples:
Hydrogenous - ExamplesHydrogenous - Examples
Manganese Nodules
Sea salt
Oolitic sand
Cosmogenous – microtektitesCosmogenous – microtektites
• Tektites – result from collisions with micrometeorsTektites – result from collisions with micrometeors– Fragments of Earth’s crust melt and spray outward from impact craterFragments of Earth’s crust melt and spray outward from impact crater– Crustal material re-melts as it falls back and forms glassy tektitesCrustal material re-melts as it falls back and forms glassy tektites
• Sediments derived from extraterrestrial material Sediments derived from extraterrestrial material (micrometeorites)(micrometeorites)
Microtektites
• Widespread but not abundantWidespread but not abundant