EXPLORING THE SEA FLOOR Lesson 5

MAPPING THE OCEAN FLOOR

Watch and take notes

MAPPING THE OCEAN FLOOR QUIZ 1)When the ocean is emptied, what does the sea floor look like?

2)What device is used to take samples from the ocean floor?

3)What device is used to map the ocean floor in detail?

4) What was the significance of the electronic jellyfish on the ROV?

5)Where did the Dumbo octopus get its name?

6)What are underwater volcanoes called?

7)Where do you find deep sea corals?

8)How tall are the corals in the strait of Fl?

9)What is the mid-oceanic ridge?

10)Where is it exposed?

11) What is the largest underwater landscape?

WORLD OCEANThough generally described as several 'separate' oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the World Ocean or global ocean. This concept of a continuous body of water with relatively free interchange among its parts is of fundamental importance to oceanography.

THE MAJOR OCEANIC DIVISIONS (LARGEST

TO SMALLEST):

OCEAN What do you notice about this picture?

OCEAN FLOOR Flat and Lifeless?

Varied Landmarks and full of Life?

SEA LEVEL Ocean’s average height relative to land.

Throughout history sea level has changedShifts in climateGrowing or shrinking ice capsIce ages = more landMore water frozen in ice

Warm periods = less landMore water is liquid

OCEAN Average Depth is ~12,081 ft

Deepest part of the ocean Mariana Trench

(~36,200 ft)

Same as on land Hills, valleys, mountains, etc

Ocean is home to tallest mountains, widest plains and deepest valleys

BATHYMETRY Characteristics of the ocean floorThe surfaces of the Moon and Jupiter have been mapped more thoroughly than the floor of the sea.

OCEAN FLOOR Mt Everest vs. Mauna KeaWhich one is which?

THE VAST UNKNOWN

On January 7, 2005, only 400 miles from its base on Guam, the navy submarine USS San Francisco was traveling about 35 mph when it slammed into an uncharted mountain about 6,000 feet beneath the surface.

One crew member died and 23 others were injured.

OCEAN FLOORThe familiar landscapes of continents are mirrored, and generally magnified, by similar features in the ocean basin.

The largest underwater mountains, for example, are higher than those on the continents.

Underwater plains are flatter and more extensive than those on the continents.

All basins contain certain common features that include oceanic ridges, trenches, abyssal plains, and volcanic cones.

SEAFLOOR FEATURES

1) CONTINENTAL MARGIN Region closest to land that is made up of 3 parts.

1A) CONTINENTAL SHELFGently sloping land area along the edges of continents

1B) CONTINENTAL SLOPE

Steep slope leading from the edge of a continent down to the seafloor

1C) CONTINENTAL RISE

Hill of sediment at the bottom of the steep slope near the edges of continents

2) ABYSSAL PLAINSFlat, featureless plain making up a large part of the seafloor

SEAFLOOR SEDIMENTS

Covering the abyssal plains are seafloor sediments that have different origins.3 types:1) Terrigenous – Consists of mineral grains eroded from land.2) Biogenous – Consists of shells and skeletons of marine animals and algae.3) Hydrogenous – Consists of minerals that crystallize directly from ocean water.

3) MID-OCEAN RIDGE

Underwater mountain range, where new seafloor is created.Atlantic Mid-Ocean Ridge is largest in the world

OCEAN RIDGESIn most locations, oceanic ridges are 2,000 meters or more below the surface of the oceans.

In a few places, however, they actually extend above sea level and form islands. Iceland, the Azores (about 900 mi. off coast of Portugal), and Tristan de Cunha are examples of such islands.

4) MID-OCEAN RIDGE

Scientists believe ocean ridges are formed when magma emerges from Earth’s interior, a process known as seafloor spreading.

Alfred Wegener developed continental drift theory, Pangaea

Which led to Harry Hess’s proposal of seafloor spreading

5) TRENCHESDeepest feature of the ocean, plunging deep below the seafloor.Trenches are long, narrow, canyon like structures, most often found next to a continental margin. They occur much more commonly in the Pacific than in any of the other oceans. The deepest trench on Earth is the Mariana Trench, which runs from the coast of Japan south and then west toward the Philippine Islands—a distance of about 1,580 miles.The British naval vessel, Challenger II surveyed the trench in 1951 and named the deepest part of the trench, the "Challenger Deep".

5) TRENCHESIts deepest spot is 11,033 meters below sea level called the Challenger Deep in the Marianas Trench.

Earthquakes and volcanic activity are commonly associated with trenches.

Mariana Trench Video – 45 min

6) VOLCANIC CONESOcean basins are alive with volcanic activity. Magma flows upward from the mantle to the ocean bottom not only through rifts, but also through numerous volcanoes and other openings in the ocean floor.

a) Seamounts are submarine volcanoes and can be either active or extinct.

b) Guyots are a specific type of seamount with a flattened top. Extinct volcanoes that were once above sea level but have since receded below the surface. As they receded, wave or current action eroded the top of the volcano to a flat surface.

7) SUBMARINE CANYON Steep-sided underwater valley near the edge of a continent.

OCEAN We know more about our moon and Mars than our Ocean

Only Mapped 10% of the ocean floor

Why?

OCEAN The moon and mars we can see

Ocean we cannot…water impedes a lot Pressure visual, etc

Need to understand this Shipping routes National security Animals migrations

Earth’s final frontier

EARLY MEASUREMENTS

Line with a weight on the end Knots tied at different points Throw overboard and see at what knot the line is at and record Knots are called Plumb lines

Early maps of the ocean floor

POST WORLD WAR I MEASUREMENTS Sound Waves Sonar – Sound Navigation and Ranging Use echoes Sounds “pings” bounce off the floor and time return Like sound in an empty classroom versus a gym Must know how fast sound travels in water

Early Mapping of Red Sea

SONAR PING

http://www.us-satellite.net/marinescience/resources_nat/audio_video/lesson6/sonar.mp3

SOUND IN WATER

Sound in water travels much faster than sound in air travels Avg speed is 1500 m/s (3000 miles per hour) Air = 340 m/s

Can measure depth using: D= (1/2) T*V Sea depth = ½ Time * Velocity ½ because 1T = surface to floor and then floor to surface

TODAY’S SONAR Sophisticated Sonar technology Locates shipwrecks, downed planes, schools of fish

Side Scan and Multibeam

SIDE SCAN

Tow fish dragged behind a ship or attached to submersible

Computer generates image Receives INTENSITY rather than basic sonar Hard objects = more intense beams

Metal ship and rocks

Soft objects = less intense Mud and Sand

Black areas are acoustic shadows…no sound

Pictures of Seafloor, but not depth

Good at locating

MULTIBEAM Depth Measurements

Emit pulse of sound from ships hull Data are recorded at a wider angle

Different Depths = Different Colors

MULTIBEAM

http://www.us-satellite.net/marinescience/resources_nat/audio_video/lesson6/Multibeam_720@24fps-300Kbps.mov

LAB: A CLASSROOM MODEL OF THE OCEAN FLOOR Page 95-97

ECHOLOCATION

Animals that are unable to see in the dark

Determine distance and direction of objects

Bats = find food or navigate trees or caves

Toothed Whales Send out clicks Sound travels more efficiently in water than air MELON in their head

Large fatty organ Focuses the sound Sounds received from cavities in lower jaw

Echolocation

SLOW PROCESS Ocean is so immense Very difficult and expensive to cover entire floor

Use data from space Highs and lows of sea surface mirror seafloor

Use satellites to measure underwater topography = BATHYMETRY

A FEW MORE DETAILS Need to look at ocean topography to understand why and where animals migrate, how things are related and what is going on there with currents, weather etc

SEA LEVEL CHANGES Sea Level changes throughout history have changed the geography of the land and the continental shelves North America was once covered by a sea Coral Fossils in Boulder mountains

SEAFLOOR SEDIMENTS Diverse and complex

Variety of abiotic and biotic factors

Differ depending on the type of material they come from Land = TERRIGENOUS sediments Living organisms = BIOGENOUS sediments Smaller portion from chemical reactions

SOILS Terrigenous sediments are primarily abiotic materials (rock & debris) that are broken down

Carried by water, wind or ice (erosion) to the ocean

As they move, they bump against other objects Smoothing the surface

Composition depends on the parent material White vs black beaches?

SEDIMENT TYPES

Black Soil – Hawaii – Eroded volcanic rock

White – Quartz based from granite rock or biogenous

SEDIMENT Biogenous comes from broken parts of shells of marine organisms

Common source is from microscopic phytoplankton

Where there are lots of plankton Sea floor is typically biogenous Some white sand beaches made exclusively of these

Some biogenous sediments come from weathering of coral reefs Open ocean, as quartz and terrestrial materials is limited the farther you go

SEDIMENTS TELL US HISTORY Information about physical ocean science processes, biological health and past climate

SEDIMENTS

HYDROGENOUS sediments Precipitate out of seawater Very mineral-rich

COSMOGENOUS sediments Dust and large particles from space Very tiny fraction

SEDIMENTS AND MIGRATIONS Sediments are important for animal travels Some feed on resources in certain soils and others have to dive deeper

OCEAN ZONES The ocean can be divided into two basic regions:

A. Pelagic Zone (anywhere in the water column)

B. Benthic Zone (the seafloor)

PELAGIC ZONE The Pelagic Zone is further divided horizontally into:

1.Neritic Zones (Coastal oceans) – Nearshore.- large variety of conditions- Salinity can increases by evaporation, or decrease

from river input- Temperature changes rapidly- Most biologically productive part of the sea

2.Oceanic Zones (Open Ocean) – Offshore.- Open ocean- 90% of the world’s ocean

PELAGIC ZONE

Can also be divided vertically into:

A.Epipelagic zone – (0-200 meters)

B.Mesopelagic Zone (200–1000 meters)

C.Bathypelagic Zone – (1000-4000 meters)

D.Abyssalpelagic Zone – (4000-6000 meters)

E.Hadalpelagic – (6000 – 10,000 meters)

SPLASH ZONE

Supralittoral (splash zone) – rarely if ever covered with waterIntertidal/littoral Zone – Regularly submerged and exposed with the fluctuating tide levelsSublittoral (sub – tidal) Zone – which extends to the edge of the continental shelf.

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LIGHT PENETRATIONEuphotic Zone (Photic Zone)Primary production occurs, light penetrates to 200m

Dysphotic ZoneSome light penetration, 200-1000m

Aphotic ZoneZero light penetration, >1000m