Transcript The Seafloor (69)

The Seafloor (69)
Contiental Shelf
• Ocean basins, which
are low areas of Earth
that are filled with
water, have many
different features.
• The continental shelf
is the gradually sloping
end of a continent that
extends under the
ocean as deep as 350
meters.
• Beyond the shelf, the
ocean floor drops more
steeply, forming the
continental slope.
• The continental slope
extends from the outer
edge of the continental
shelf down to the
ocean floor.
• Beyond the continental slope lie the
trenches, valleys, plains, mountains, and
ridges of the ocean basin.
• In the deep ocean, sediment, derived mostly
from land, settles constantly on the ocean
floor.
• These deposits fill in valleys and create flat
seafloor areas called abyssal plains.
• Some areas of abyssal plains have small
hills and seamounts.
• Seamounts are underwater, inactive
volcanic peaks.
Ridges and Trenches
• Mid-ocean ridges can
be found at the bottom
of all ocean basins.
They form a continuous
underwater ridge
approximately 70,000
km long.
• A mid-ocean ridge is
the area in an ocean
basin where new
ocean floor is formed
• As crustal plates move, the ocean floor
changes.
• When ocean plates separate, hot magma
from Earth’s interior forms new ocean crust.
• New ocean floor forms along mid-ocean
ridges as lava erupts through cracks in
Earth’s crust.
• When the lava hits the water, it cools quickly
into solid rock, forming new seafloor.
Subduction Zone
• On the ocean floor,
subduction zones are
marked by deep ocean
trenches.
• A trench is a long,
narrow, steep-sided
depression where one
crustal plate sinks
beneath another.
• http://www.youtube.com/
watch?v=wP380-Iaoos
Life in the Ocean
• Marine organisms such as plants and algae use
energy from the Sun to build their tissues and
produce their own food.
• This process of making food is called
photosynthesis.
• Chemosynthesis involves using sulfur or nitrogen
compounds as an energy source, instead of light
from the Sun, to produce food.
• Bacteria that perform chemosynthesis using sulfur
compounds live along mid-ocean ridges near
hydrothermal vents where no light is available.
http://www.youtube.com/watch?v=X
otF9fzo4Vo
• Marine organisms that drift with the currents are
called plankton.
• Plankton range from microscopic algae and
animals to organisms as large as jellyfish.
• Most phytoplankton plankton that are
producersare one-celled organisms that float
in the upper layers of the ocean where light
needed for photosynthesis is available.
Plankton
• One abundant form of
phytoplankton is a
once-celled organism
called a diatom.
• Diatoms and other
phytoplankton are the
source of food for
zooplankton, animals
that drift with ocean
currents.
Coral Reefs
• Corals thrive in clear, warm water that receives a
lot of sunlight.
• Each coral animal builds a hard capsule around
its body from the calcium it removes from
seawater.
• Each capsule is cemented to others to form a
large colony called a reef.
• A reef is a rigid, wave-resistant structure built by
corals from skeletal material.
• https://www.youtube.com/watch?v=wbNeIn3vVK
M
• What is the continental shelf?
• The continental shelf is the gradually
sloping end of a continent that extends
under the ocean.
• Which structure extends from the outer
edge of the continental shelf to the ocean
floor?
– A. abyssal plain
– B. continental slope
– C. oceanic trench
– D. seamount
• What is the area in an ocean basin where
new ocean floor is forming?
• New seafloor forms at mid-ocean ridges
as lava erupts through cracks in Earth’s
crust.
• Which process involves using sulfur or
• nitrogen compounds as an energy source
to produce food?
– A. chemosynthesis
– B. nitrosynthesis
– C. photosynthesis
– D. sulfurosynthesis