Transcript the ocean floor - NVHSEarthScienceKDudenhausen

THE OCEAN FLOOR
1. Oceanography – the study of
the world’s oceans
Nearly 71% of the earth’s surface is covered
by oceans
The world’s oceans:
•
Pacific- the largest and deepest
•
Atlantic – half the size of Pacific
•
Indian – almost entirely in Southern
hemisphere
•
Arctic – smallest and shallowest
2. Mapping the Ocean Floor
• Bathymetry-the measurement of ocean
depths and the charting of the shape or
topography of the ocean floor
• Sonar – sound waves are transmitted
toward the ocean floor and the time of
echo reflections are measured
• Satellites – the ocean surface is not flat
• Submersibles
3. Ocean Floor Features
Continental Margins
• Continental Shelf – the gently sloping submerged
surface extending from the shoreline, location of
important mineral deposits, oil and gas, and huge sand
and gravel deposits
• Continental Slope – steeper, marks the boundary
between continental crust and oceanic crust
Submarine canyons – cut into continental slope, deep
sided valleys, eroded by turbidity currents
Turbidity currents are occasional movements of dense,
sediment rich water down the continental slope
• Continental rise – gently sloping
Ocean Basin Floor
• Deep ocean trenches – formed by subduction, deepest
known place on Earth is the Challenger Deep of the
Mariana Trench, 11,022 meters deep
• Abyssal plains – extremely flat, most level places
• Seamounts – submerged volcanic peaks
• Guyots – once active, now submerged, flat topped
remnants of volcanoes
• Mid-Ocean Ridges – found near the center of most
ocean basins
• Sea-floor spreading – occurs at divergent plate
boundaries, new crust is being formed
• Hydrothermal vents – form along mid-ocean ridges,
mineral-rich hot water comes in contact with cold water
and metals are deposited
4. Seafloor Sediments
• Terrigenous sediment – mineral grains eroded from
continental rocks and transported to the ocean, large
particles of sand and gravel deposited near shore, fine
particles take years to settle
• Biogenous sediment – consist of shells and skeletons on
marine animals and algae
Calcereous ooze – produced by calcium carbonate
shells of organisms
Siliceous ooze – produced by the shells of diatoms
(shells made of silica)
• Hydrogenous sediment – consists of minerals that
crystallize directly from ocean water
Manganese nodules
Calcium carbonate (limestone)
Evaporites
5. Resources From the Ocean
Floor
• Oil and Natural Gas – more than 30% of our oil
and natural gas supplies are from offshore
reserves
• Gas hydrates – created when bacteria break
down organic matter trapped in ocean floor
sediments
• Sand and gravel
• Manganese nodules
• Evaporative salts – when seawater evaporates,
the salts precipitate out of solution, the most
economically important is halite