Download Earth Science Common Assessment #8

Earth Science Common
Assessment #8
Oceans and other Salty Stuff
12 easy* questions
*If you can remember my presentation!
Submarine Topography
• The shape of the ocean floor is known to
scientists as submarine topography. The floor
contains mountains, plains, canyons, plateaus,
basins, and other topographic features that
are found on land. Usually, the ocean bottom
is divided into three major zones: the
continental margin*, the ocean-basin floor*,
and the mid-ocean ridge*.
The 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.
Higher Salinity*
• What do you think the factors for higher
salinity might be?
Seamounts*
What are seamounts?
Seamounts are undersea
mountains
Usually of volcanic origin rising
from the seafloor and
peaking below sea level.
A seamount tall enough to
break the sea surface is
called an oceanic island,
e.g., the islands of Hawaii,
the Azores and Bermuda
were all underwater
seamounts at some point in
the past.
Seamounts are undersea mountains
Why are seamounts so important?
• Seamounts are hotspots of marine life in the
vast realms of the open ocean. As they stand
proud of the surrounding seabed they tend to
concentrate water currents and they can have
their own localized tides, eddies and
upwelling's (where cold, nutrient-rich,
deepwater moves up along the steep sides of
the seamount).
SO?
Marine mammals,
sharks, tuna and
cephalopods ,
and even seabirds
all congregate
over seamounts to
feed on the rich
booty of marine
life.
Summary
Seamounts
http://www.montereyinstitute.org/noaa/lesso
n15.html -
Upwelling*
• Upwelling is the process by which subsurface
water is brought to the surface.
• Upwelled water is usually colder, saltier, and
often has higher concentrations of nutrients and
dissolved oxygen than the water it replaces.
• Nutrients provided by upwelling promote the
growth of phytoplankton which form the basis of
the marine food chain.
• Many of the world's major fisheries are located
in areas where strong persistent upwelling
occurs.
Abyssal Plains* are the most level places
on Earth
• Science and the Sea - Abyssal Plains
Abyssal Plains*
• There are several distinct abyssal plains across the world's
oceans.
• Each abyssal plain starts at a continental rise and continues
until it reaches a mid-oceanic ridge, resuming on the other
side.
• Mid-oceanic ridges are huge underwater mountain chains
marking major plate boundaries.
• These ridges are also the primary source of seafloor
spreading, since they are slowly pulling apart.
• Since the continental slope and the ridges essentially form the
edge of a deep bowl, some people refer to the abyssal plain
as the ocean basin.
• Overall, the abyssal plain represents around 40% of the
ocean floor.
Abyssal Plains*
• While some people visualize the abyssal plain as
desert-like, this characterization is far from the truth.
• The environment is actually teeming with life, since a
multitude of organisms have adapted to the intense
conditions.
• Organisms which live on or around the abyssal plain
have specialized body structures which are designed to
handle the pressure, and they often look unusual and
fantastic; photographs and drawings of these creatures
could be mistaken for alien life.
Thermocline* a transition layer
between deep and surface water
• The thermocline is the
transition layer between the
mixed layer at the surface and
the deep water layer.
• The definitions of these layers
are based on temperature.
• The mixed layer is near the
surface where the
temperature is roughly that of
surface water. In the
thermocline, the temperature
decreases rapidly from the
mixed layer temperature to
the much colder deep water
temperature.
http://www.encyclopedia.com/video/FuOX23yX
hZ8-ocean-odyssey-density-current.aspx
• Video About Ocean Odyssey - Density Current
| Encyclopedia.com
Oxygen*
• Is supplied to deep-sea life by density currents
that form at the surface and then sink
The Continental Shelf
The Continental Shelf*
• The continental shelf is the gently sloping undersea
plain between a continent and the deep ocean.
• The continental shelf is an extension of the continent's
landmass under the ocean.
• The waters of the continental shelf are relatively
shallow (rarely more than 150 to 200 meters deep)
compared to the open ocean (thousands of meters
deep).
• The continental shelf extends outward to the
continental slope where the deep ocean truly begins.
Distinct Marine Life Zones
Available
sunlight, water
depth, and the
distance from
shore all
determine
Marine Life
Zones
Latitude* is not a factor in determining marine life zones
The oceanic trenches
• The oceanic trenches are long but narrow
topographic depressions of the sea floor.
Trenches are the deepest parts of the ocean
floor.
The oceanic trenches*
• A deep-sea trench is a narrow, elongate, v-shaped
depression in the ocean floor. Trenches * are the
deepest parts of the ocean, and the lowest
points on Earth, reaching depths of nearly 7 mi
below sea level.
• These long, narrow, curving depressions can be
thousands of miles in length, yet as little as 5 mi
in width.
• Deep-sea trenches are part of a system of
tectonic processes termed subduction.
Salinity
• The salinity of ocean water varies.
• It is affected by such factors as melting of ice,
inflow of river water, evaporation, rain,
snowfall, wind, wave motion, and ocean
currents that cause horizontal and vertical
mixing of the saltwater.
HOW SALTY IS THE OCEAN?...
• Some scientists estimate that the oceans
contain as much as 50 quadrillion tons (50
million billion tons) of dissolved solids.
• If the salt in the sea could be removed and
spread evenly over the Earth's land surface it
would form a layer more than 500 feet thick,
about the height of a 40-story office building.
THE SALTIEST WATER*...
•
The saltiest water occurs in the Red Sea and
the Persian Gulf, where rates of evaporation
are very high*.
What can make the ocean SALTIER?
• Salts become concentrated in the sea because
the Sun's heat (temperature*) distills or
vaporizes almost pure water from the surface
of the sea and leaves the salts behind.
• This process is part of the continual exchange
of water between the Earth and the
atmosphere that is called the hydrologic cycle.
The density of sea water depends on:
• Temperature* ,
• Salinity and
• Pressure , which increases with water depth.
Properties of Seawater
• Seawater is ordinary water (H2O) containing
dissolved mineral salts in an average
concentration of 3.5 per cent by weight.
• Seawater also contains numerous organic and
inorganic particles in suspension (undisovled).
• The mineral salts come from eroded rocks. Much
of the rock debris resulting from erosion is
ultimately carried to the sea by rivers, glaciers,
and winds, and thus several billion tons of salt are
added to the sea each year.
Depths
• The floor of some ocean basins may lie 18,000 to 20,000 feet or
more beneath the surface.
• The greatest depths, however, occur not in the central portion of
the ocean but in trenches—long, narrow, deep cracks in the ocean
bottom that are usually found near continents and on the seaward
side of island chains.
• The greatest known depth of any ocean is in the Challenger Deep of
the Mariana Trench in the Pacific Ocean, about 250 miles southwest
of the island of Guam.
• It was discovered in 1951 by the British survey ship Challenger,
which reported a depth of 35,760 feet.
• Later expeditions from various countries have reported even
greater maximum depths. Recorded echo soundings indicate a
maximum depth of about 36,000 feet. It was in these same waters
that the Trieste made its record descent in 1960.