Pink Sea-Through Fantasia
Warm Up 1/28
1. What does SCUBA stand for?
2. Why does the establishment of ocean front
research centers represent a significant step
forward in marine science?
3. What tool utilized on the HMS Challenger
was rendered obsolete by the invention of
sonar?
The Sea Floor
• Oceans cover 71% of the planet, and regulate the
climate and atmosphere.
• Oceans are classified
into four large basins.
– Pacific- deepest and
largest ocean. Almost
as large as all others
combined.
– Atlantic- Larger than
the Indian ocean, but
the two are similar in
average depth.
– Arctic- smallest and
shallowest ocean.
• Oceanographers often speak
of a single WORLD OCEAN.
• Connections among the
major basins allow seawater,
materials, and some
organisms to move from one
ocean to another.
• There is also now a Southern
ocean, this is the body of
water that surround the
Antarctic.
Structure of the Earth
• The Earth is thought to have originated 4.5 billion
years ago from a collection of dust in space.
• This generated tremendous heat and formed a
molten ball.
• Materials sorted out by their density.
Earth’s Internal Structure
• Core
– Mostly Iron
– Solid Inner core
– “liquid” Outer core
– Movement of outer
core thought to cause
Earth’s Magnetic Field.
Earth’s Internal Structure
• Mantel
– Mostly solid
– Near melting point of
rock so there is some
flow and movement
over hundreds of
millions of years
• Crust
– Outer most layer of Earth
– Thin, rigid skin floating
on mantle.
– 2 types
• Oceanic- thinner and
denser, oldest rocks are
~200 million years old.
• Continental- thicker and
less dense, oldest rocks
are ~3.8 billion years old.
Continental Drift
• Puzzle like shape of continents noted by Francis
Bacon in 1620
• Alfred Wegner proposed continental drift
hypothesis in 1912
– Proposed the Pangaea “supercontinent”
Plate Tectonics
• Evidence for continental drift continued to
accumulate.
• WWII, sonar surveys of ocean floor revealed the
Mid-ocean ridge system.
•A continuous chain of submarine volcanic mountains
that encircles the globe.
•Largest geological feature on Earth.
Example is the Mid-Atlantic Ridge
• Iceland is a gigantic submarine volcano that is part
of this system.
What does an Oceanographer Do?
Compass jellyfish (Chrysaora hysoscella)
Warm-Up 1/29
1. What is the largest geological feature on the
planet?
2. Which ocean does not have an oceanic basin
associated with it?
3. Why is continental crust dry land?
Warm Up 1/30
1. What is the name for the rigid outer layer of
the planet Earth?
2. What is the name for the movement of the
outer surface of the planet Earth? (recall this
from earth science.)
3. Which oceanic basin is the largest?
• Sea floor rock at the ridge is very young and gets
progressively older moving away from the ridge.
Right at the ridge crest there is little if any sediment. Loose
material like sand and mud that settles to the bottom.
But sediment gets thicker and older at greater distance from the
ridge.
• Magnetic field of the earth flips polarity every
300,000 years or so, due to changes in the motion
of the outer core.
• Sea-floor rocks have symmetric patterns of
magnetic bands of stripes that run parallel to the
mid-ocean ridge.
• These magnetic abnormalities could only have
formed if the normally magnetized rock cooled
from molten material at different times than the
reverse magnetize bands.
• Evident that the sea floor was not created all at
once.
• Cracks in the crust called rifts form from the
separating of the oceanic crust.
• This releases some pressure on the underlying
mantle this causes the crust to rise and push up
forming mountains (ridges)
• Liquid mantle rises through these rifts and cools
forming new sea floor.
• This continues as the sea floor moves away and new
sea floor is made. This process is called sea-floor
spreading.
• As plates move through this process they can drag
the continents along with them providing a
mechanism for continental drift.
• A trench, deep depressions in the sea floor, is
formed when two plates collide and one of them
dips below the other in a process known as
subduction.
• As new oceanic plate is created, old is destroyed.
Think for a moment….
• What happens when a continental and oceanic
plate collide?
• Why?
• How does this explain the age differences observed
between the rock composing the two plate types?
• As the plate sinks into the mantel, in an area known
as a subduction zone, it melts
• Some of this material rises back up to the surface to
form volcanoes.
Volcanic island chains associated with the trenches
follow the trenches curvatures and are called island
arc.
Examples: Aleutian and Mariana Islands
What does an Oceanographer Do?
• Continue work.
Records in the Sediment
• The type of sediment on the sea floor often reflect
conditions in the ocean above.
• Studying this gives a wealth of information about
Earth’s Past.
Types of Sediment
• Lithogenous sediment- derived from the physical
and chemical breakdown (weathering) of rocks,
mostly on the continents.
• Biogenous sediment- composed of the remains of
marine organisms. Made mostly of calcium
carbonate or silica.
• Biogenous sediments can be carbon dated to
determine age.
• Water temperature can also be determined by
measuring ratios of different elements in the
organism’s remains.
• These sediments can provide a detailed record of
Earth’s past climate!
Divisions of the sea floor
• The sea floor can be divided into two types.
– The continental margins- the submerged edges of the
continents
– The deep-sea floor
Continental Margins
• Boundaries between continental and oceanic crust.
• Consist of:
– Continental Shelf- shallow gently sloping area.
– Continental slope- steeper sloping area
– Continental rise- gently sloping region at the base of the
continental slope.
Continental Shelf
• Shallowest part of the continental margin.
• Only 8% of ocean surface area, contains the most
life and biological activity.
• Ends at the shelf break, an area where the slope
suddenly gets steeper.
Continental Slope
• Begins at shelf break and descends down to the
deep sea floor.
Continental rise
• Consist of a thick layer of sediment pile up on the
sea floor.
Deep-Ocean Basins
• Most of it is at a depth of 3000-5000m
• Also known as abyssal plain.
• Very flat, slopes up slightly toward the mid-ocean
ridge.
Marine Volcanoes
• Submarine volcanoes are called seamounts.
• If they break the surface they can become volcanic
islands.
• These islands can then become guyots.
• Flat-topped seamounts called guyots (gee-ohs). These were once
islands but are now several hundred meters beneath the sea due
to rising sea levels and lithosphereic sinking.
Mid-Ocean Ridge and Hydrothermal Vents
• In the centre of the mid-ocean ridge where the
plates are pulling apart, there is a gap or depression
known and the central rift valley.
• Area around this valley is cracked and fractured.
• Seawater enters these cracks and is heated by the
mantle.
• This superheated water then forces it way back up
through the surface forming hydrothermal vents.
• Water is often significantly warmer than
surrounding water.
• Some vents the water is 350 degrees Celsius (660)
and actually started to melt the first thermometer
scientists attempted to use to measure it.
• Water is rich in dissolved minerals, mainly sulfides.
• When this water hits the cold ocean water it rapidly
cools and causes the minerals to solidify and form
structures around the vents.
• Black smokers are chimney like structure that
progressively build up around a vent as the mineral
solidify.
• The “smoke” is
actually a dense cloud
of mineral particles.
• Also existing:
– White smokers
– Snowblowers
– Blue smokers
• Astounding life lives
around these things!