Download Chapter 19-The Water Planet

Chapter 19-The Water
Planet
Global Ocean:
• The body of salt water that covers nearly
¾ our Earth’s surface.
• Only Earth can be called the water
planet—why is that so?
• No other known planet has this similar
covering of water.
We have 5 major oceans:
• Atlantic-2nd largest ocean-3.9 km average
depth.
• Pacific-largest ocean-1/2 of all ocean water that
is on Earth and is the deepest at average depth
of 4.3 km.
• Indian-3rd largest with average depth of 3.9 km.
• Arctic-Smallest ocean & surrounds the North
Pole.(20 could fit in the Atlantic). Covered in ice
most of the year.
• Southern Oceans-extend from the coast of
Antarctica to 60 degrees S. latitude.
The Oceans
What is a Sea?
• A large, commonly saline body of water
that is smaller than an ocean and that may
be partially or completely surrounded by
land.
• Examples: Mediterranean, Caribbean,Red
Sea, and South China Seas.
Seas”
Features of the Ocean Floor
• The continental margins are shallow parts
of the ocean floor that are made of
continental crust and a thick wedge of
sediment.
Continental shelf
• Most continents are outlined with shallow water that
covers the edge of the continent. The part of the
continent covered by water is the continental shelf. At the
seaward edge is a steep slope called the continental
slope.
Continental shelf:
Changes in sea level affect the
continental shelves.
• Glacial periods-the ice holds large
amounts of water so the sea level falls and
exposes more of the continental shelf—
this can be weathered and eroded.
• If the ice melts water is added and the sea
level rises and covers the continental
shelf.
Continental Slope:
• A steep slope. The boundary between the
continental crust and the oceanic crust is located
at the base of the continental slope.
• The ocean depth increases by several thousand
meters within a distance of a few kilometers.
• See next slide. . . . .
Here you go----
What is happening at the slope?
• The depth greatly increases.
• Sometimes there are great deep V-shaped
valleys—these are called submarine
canyons.
Submarine canyons are often
found at the mouths of major rivers
Turbidity currents:
• Are dense currents that carry large amounts of
sediment down the continental slopes.
• These form when earthquakes cause
underwater landslides or when a large sediment
load runs down a slope.
Underwater landslide
Underwater slide:
Deep-ocean basin
• The part of the ocean floor that is under deep water
beyond the continent margin and that is composed of
oceanic crust and a thin layer of sediment.
• Will incorporate into Indian ocean.
Features of Deep Ocean Basins
• Broad flat plains; submerged volcanoes; gigantic
mountain ranges; and deep trenches.
Trenches
• Long, narrow depressions located in the deep-ocean
basins.
• Mariana Trench in western Pacific is the deepest place in
Earth’s crust.
Abyssal Plains
• Oceans about 4 km deep here.
• Cover ½ of the deep-ocean basins
and are the flattest regions on Earth.
Depths are from 3 m to over 1,300
km.
• Layers of sediment cover the bottom
& are carried by ocean currents and
wind brings some from the continents.
What else settles to the bottom?
• Organisms that live in the ocean and die.
How thick are the sediments?
• Determined by three things:
– Age of the ocean crust. Older = thicker
– Distance from continental margin to the
abyssal plain.
– If the area is bordered by a trench. (thinner)
Mid-Ocean ridges
• These are the most prominent features of
ocean basins. They form underwater
mountain ranges.
Can mid-ocean ridges rise above
sea level?
• Yes .. . . .Ireland is one area
Abyssal hill
• Fault-bounded blocks of crust that form
parallel to the ridges as the lithosphere
cools and contracts.
Fracture zones
• Ridges break into segments when plate motions
change directions. This causes rough
topography which runs perpendicular across the
ridge.
Seamounts
• Any submerged volcanic mountain that is taller than 1
km.
• Form in areas of hot spots.
• Seamounts that rise above the ocean surface form
oceanic islands.
Guyots
• These are seamounts that have moved
with the tectonic plate away from the hot
spot. The island sinks and is eroded by the
waves to form flat-topped submerged
seamounts.
• Before a seamount becomes a guyot,
there is an intermediate stage. These are
called “atolls”.
Guyot
Ocean floor sediments
Where do they come from?
• Rivers, shorelines, and dead organisms.
• Sediments are sorted by size.
• Coarse gravel and sand are usually found close
to shore.
• Why? They are heavy and do not move easily.
What about the lighter sediments?
• They remain suspended in water and are
deposited at great distances from the
shore.
• Sediments in the deep ocean basin
(beyond the continental margin) are
generally finer than those found in shallow
water.
What is a core sample?
• Cylinders of sediment that are collected by
drilling into sediment layers on the ocean floor.
• Sediments can be organic or inorganic.
• Inorganic may be rock particles carried from
land by rivers.
• Some may be fine particles of rock and volcanic
ash which may have been blown out by the
wind.
What else provides sediments?
• Icebergs! They pick up rocks on their
downward travels and when they break
and drift to sea, melting occurs and debris
drops.
What else can give up debris to the
oceans?
• Meteorites-the cosmic dust that is left falls
to Earth’s surface, hits the oceans and
sinks.
Biogenic sediments
• This means the sediments were originally produced by
living organisms.
Diatoms and radiolarians are microscopic organisms that
leave silica sediments and foraminiferans leave calcium
carbonate sediments.
Nodules
• Potato shaped lumps that form from
substances that have dissolved and
crystallized. Formed mostly from
manganese, nickel, copper and iron.
• Commonly found on the abyssal plains.
Physical classification of sediments
• 2 basic types:
• Muds-very fine silt/clay-sized particles of
rock. (red clay is very common)
• 40% of the ocean floor is covered with
ooze.
• 2 types calcareous ooze and siliceous
ooze
By the way, what is a continental
rise?
• The continental rise is an underwater feature
found between the continental slope and the
abyssal plain. This feature can be found all
around the world, and it represents the final
stage in the boundary between continents and
the deepest part of the ocean. The environment
in the continental rise is quite unique, and many
oceanographers study it extensively in the
hopes of learning more about the ocean and
geologic history
Continental Rise
Your Assignment
• Using page 476-477 as a guide (9th grade book) draw a picture of
the ocean floor. Do your best work. Do this on a minimum size of
81/2 x 11 sheet of paper. It can be larger if you want.
• Label all the parts and number them as the list below shows:
• On the back of your paper you will need to write the definition for
each of the parts: (1) Continental shelf; (2) Continental slope;(3)
Continental rise; (4) Submarine canyon; (5) Abyssal plain; (6) Midocean ridge; *(7) Guyot; and (8) Trench.
•
You will also need do draw a (9) seamount, and (10) atoll. Draw
these by the *(7)guyot to show the correct order of formation. Do not
forget your definitions of each added onto the back of your paper or
on another sheet and stapled to your drawing.
Due date is Thursday, Feb. 19th.