Ocean FeaturesOcean Features

BathymetryBathymetry

BathymetryBathymetry-(Bathos=depth;metry--(Bathos=depth;metry-measurement) Measurement of measurement) Measurement of ocean depths and charting the shape ocean depths and charting the shape of the ocean floorof the ocean floor

SoundingSounding- Using a line with heavy - Using a line with heavy weight to probe ocean’s depthsweight to probe ocean’s depths– FathomFathom- unit of measurement - unit of measurement

specifically for ocean depth specifically for ocean depth measurement (1 fathom=1.8 meters=6 measurement (1 fathom=1.8 meters=6 feet)feet)

HMS ChallengerHMS Challenger

1872- made first systematic 1872- made first systematic measurements using sounding measurements using sounding technologytechnology

Noticed that depth varied indicating Noticed that depth varied indicating that the ocean floor was not flat, but that the ocean floor was not flat, but had relief just as land doeshad relief just as land does

Advancing TechnologyAdvancing Technology SONARSONAR Technology- Technology- SoSound, und, NNavigation, avigation, AAnd nd

RRangeange 1900s- 1900s- Echo SoundersEcho Sounders

– Sends a sound signal to determine depth and shape of Sends a sound signal to determine depth and shape of ocean floor. Early technology not very accurateocean floor. Early technology not very accurate

1950s-1950s- Precision Depth Recorder (PDR) Precision Depth Recorder (PDR)– Used high-frequency sound beam to measure depths Used high-frequency sound beam to measure depths

within 1 meter accuracywithin 1 meter accuracy Current technology-Current technology- Multibeam Echo Sounders Multibeam Echo Sounders

– Use multiple frequencies of sound simultaneously giving Use multiple frequencies of sound simultaneously giving more precise datamore precise data

http://player.discoveryeducation.com/index.cfm?ghttp://player.discoveryeducation.com/index.cfm?guidAssetId=933F96EA-3524-4872-9335-94E264BuidAssetId=933F96EA-3524-4872-9335-94E264BD51C4D51C4

Ocean Floor ProvincesOcean Floor Provinces

Continental MarginsContinental Margins– Shallow water areas close to continentsShallow water areas close to continents

Deep Ocean BasinsDeep Ocean Basins– Deep water areas farther from landDeep water areas farther from land

Mid-Ocean RidgeMid-Ocean Ridge– Shallower areas near the middle of the Shallower areas near the middle of the

oceanocean

Continental MarginsContinental Margins

Passive MarginsPassive Margins– Imbedded within the interior of Imbedded within the interior of

lithospheric plates and are not in close lithospheric plates and are not in close proximity to plate marginsproximity to plate margins

– Lack tectonic activityLack tectonic activity Active MarginsActive Margins

– Associated with lithospheric plate Associated with lithospheric plate boundaries and are marked by a high boundaries and are marked by a high degree of tectonic activitydegree of tectonic activity

Active MarginsActive Margins

Convergent Active marginsConvergent Active margins– oceanic-continental convergent plate oceanic-continental convergent plate

boundariesboundaries– FeaturesFeatures

Continental arc, narrow shelf, steep Continental arc, narrow shelf, steep slope, offshore trenchslope, offshore trench

Transform Active marginsTransform Active margins– Transform plate boundariesTransform plate boundaries– Faults create linear islands, banks, deep Faults create linear islands, banks, deep

basinsbasins

Features of Continental MarginsFeatures of Continental Margins

Continental shelf-Continental shelf- flat zone extending flat zone extending from the shore beneath the ocean to a from the shore beneath the ocean to a point where slope angle increases point where slope angle increases dramatically dramatically – Average width- 70 KMAverage width- 70 KM– Ranges from a meters to 1500 KMRanges from a meters to 1500 KM

Shelf Break-Shelf Break- Point where increase in Point where increase in slope angle occursslope angle occurs– Can contain coastal islands, reefs, and raised Can contain coastal islands, reefs, and raised

banksbanks

Features of Continental Margins Features of Continental Margins Continental borderland-Continental borderland- occurs in occurs in

faulted areas (California). High degree of faulted areas (California). High degree of relief on shelf relief on shelf

Continental slope-Continental slope- this is where deep this is where deep ocean basins beginocean basins begin

Continental rise-Continental rise- transition zone transition zone between the continental margin and the between the continental margin and the deep ocean floordeep ocean floor– Graded bedding, produced by turbidity Graded bedding, produced by turbidity

currents. Layered sedimentation with heavier currents. Layered sedimentation with heavier sediments settling out first. Decrease in sediments settling out first. Decrease in sediment size from bottom to topsediment size from bottom to top

Underwater CanyonsUnderwater Canyons

Submarine canyons-Submarine canyons- V-shaped and have V-shaped and have branches or tributaries with steep branches or tributaries with steep overhanging wallsoverhanging walls– Thought to occur because of Thought to occur because of turbidity turbidity

currentscurrents– Turbidity currents- Turbidity currents- Underwater avalanches Underwater avalanches

of muddy water mixed with rocks and other of muddy water mixed with rocks and other debrisdebris

– Mass moves from earthquakes, hurricanes, or Mass moves from earthquakes, hurricanes, or other disturbance carving the canyonother disturbance carving the canyon

Deep OceanDeep Ocean Abyssal Plains-Abyssal Plains- Extend from the Extend from the

base of the continental rise into the base of the continental rise into the deep-ocean basins. deep-ocean basins. – Flat, depositional surfaces with very Flat, depositional surfaces with very

slight slopesslight slopes– Average between 4500 meters and 6000 Average between 4500 meters and 6000

meters deepmeters deep– Suspension Settling-Suspension Settling- fine particles of fine particles of

sediment slowly drift onto the deep sediment slowly drift onto the deep ocean floorocean floorThis is how abyssal plains formThis is how abyssal plains form

Underwater VolcanoesUnderwater Volcanoes

Seamounts: Seamounts: Below sea level, Below sea level, but rise 1 but rise 1 kilometer above kilometer above the deep ocean the deep ocean floorfloor

Seaknolls Seaknolls (abyssal hills) (abyssal hills) less than 1 less than 1 kilometer above kilometer above the deep ocean the deep ocean floorfloor

Ocean TrenchesOcean Trenches

Deep linear scars in the ocean floor. Deep linear scars in the ocean floor. They are very narrow and steepThey are very narrow and steep

Occurs along active continental Occurs along active continental margins, where there is a convergent margins, where there is a convergent plate boundaryplate boundary

The side nearest to land can be The side nearest to land can be volcanic arcs (islands of Japan), or volcanic arcs (islands of Japan), or continental arcs (Andes Mountains)continental arcs (Andes Mountains)

Mid-Ocean RidgeMid-Ocean Ridge

Earth’s longest mountain chain – Earth’s longest mountain chain – 75,000 kilometers/46,600 miles75,000 kilometers/46,600 miles

Divergent boundaryDivergent boundary Entirely volcanic- composed of Entirely volcanic- composed of

basaltic lavasbasaltic lavas Rift valley occurs along its crestRift valley occurs along its crest Underwater lava flows- Pillow lavasUnderwater lava flows- Pillow lavas

Hydrothermal VentsHydrothermal Vents

Hot springs which occur in the central rift Hot springs which occur in the central rift valleyvalley

Appearance depends on temperature of Appearance depends on temperature of waterwater– Warm-water vents are below 30Warm-water vents are below 30ooC (86C (86ooF) and F) and

are clear in colorare clear in color– White smokers are between 30White smokers are between 30ooC and 350C and 350ooC C

(86(86ooF- 662F- 662ooF) and are white in color F) and are white in color – Black smokers are above 350Black smokers are above 350ooC (662C (662ooF) and F) and

are black in color are black in color

Mid-Ocean Ridge cont.Mid-Ocean Ridge cont.

Oceanic ridgesOceanic ridges have a rift valley and have a rift valley and steep rugged slopessteep rugged slopes

Oceanic risesOceanic rises have slopes that are have slopes that are gentler and less ruggedgentler and less rugged

Mid-Ocean RidgeMid-Ocean Ridge

Transform FaultsTransform Faults cut the mid-ocean cut the mid-ocean ridge in a number of placesridge in a number of places– These faults are perpendicular to the These faults are perpendicular to the

mid-ocean ridge and give the ridge a mid-ocean ridge and give the ridge a zigzag appearancezigzag appearance

– Many earthquakes occur hereMany earthquakes occur here Fracture ZonesFracture Zones also extend from the also extend from the

mid-ocean ridge, but are much mid-ocean ridge, but are much different from transform faultsdifferent from transform faults