Seafloor and Costal
Features
TEST 10/23
VIEW OF OCEAN FLOOR
Features of the Ocean Floor
Bathymetric Picture/Reading

Study of underwater depth of lake or ocean floors.

Bathymetry is the measurement of the depth of water in oceans, rivers, or
lakes.

Bathymetric maps look a lot like topographic maps, which use lines to
show the shape and elevation of land features.
Bathymetric Maps/Pics
Continental Margins
Zone of the ocean floor that separates
the tin oceanic
Crust from the thick continental crust
Continental Shelf

Edge of a continent that lies under the ocean.

Continents are the 7 main divisions of land.

A continental shelf extends from the coastline of a continent to a drop-off
point called the shelf break. From the break, the shelf descends toward the
deep ocean floor in what is called the continental slope.

(Shelf extends toward the Continental Slope)

Most continental shelves are broad, gently slopingplains covered by relatively
shallow water.

Water depth over the continental shelves averages about 60 meters (200
feet).

Sunlight penetrates the shallow waters, and many kinds of organisms flourish—
frommicroscopic shrimp to giant seaweed called kelp.

Ocean currents and runoff from rivers bring nutrients to organisms that live on
continental shelves.
Continental Slope

A steep slope separating a continental shelf and a deep ocean basin.

The sloping region between a continental shelf and a
continental rise. A continental slope is typically about 20 km(12.4 mi) wide,
consists of muds and silts, and is often crosscut by submarine canyons.

The world's combined continental slope has a total length of
approximately 300,000 km (200,000 miles) and descends at an average
angle in excess of 4° from the shelf break at the edge of
the continental shelf to the beginning of the ocean basins at depths of
100 to 3,200 meters (330 to 10,500 feet).
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.

At the bottom of the continental slope, one will find the continental rise,
an underwater hill composed of tons of accumulated sediments. The
general slope of the continental rise is between 0.5 degrees and 1.0
degrees. Beyond the continental rise stretches the abyssal plain, an
extremely flat area of the sea floor which is also incredibly deep.
Abyssal Plain

An abyssal plain is an underwater plain on the deep ocean floor, usually
found at depths between 3000 and 6000 m.

Lying generally between the foot of a continental rise and a mid-ocean
ridge, abyssal plains cover more than 50% of the Earth's surface.

The creation of the abyssal plain is the end result of spreading of the
seafloor (plate tectonics) and melting of the lower oceanic crust. Magma
rises from above the asthenosphere (a layer of the upper mantle) and as
this basaltic material reaches the surface at mid-ocean ridges it forms
new oceanic crust. This is constantly pulled sideways by spreading of the
seafloor.
Margins

Continental Margin: Zone of the ocean floor that separates the tin oceanic crust from the thick
continental crust.

Passive Margin: the transition between the oceanic and continental lithosphere which not an active
plate margin. Passive continental margins are found along the remaining coastlines. Because there
is no collision or subduction taking place, tectonic activity is minimal and the earth's weathering and
erosional processes are winning

Active Margin: Active margins are commonly the sites of tectonic activity: earthquakes, volcanoes,
mountain building, and the formation of new igneous rock. Because of the mountainous terrain,
most of the rivers are fairly short, and the continental shelf is narrow to non-existent, dropping off
quickly into the depths of the subduction trench.
Biodiversity @ margins
https://www.youtube.com/watch?v=snkMLEgbky8
Sea Floor Features

Ridges

Vents

Trench
Ridges

A mid-ocean ridge is an underwater mountain system formed by plate tectonics. It
consists of various mountains linked in chains, typically having a valley known as
a rift running along its spine. This type of oceanic mountain ridge is characteristic of
what is known as an oceanic spreading center, which is responsible for seafloor
spreading.

Mid-ocean ridges are geologically active, with new magma constantly emerging
onto the ocean floor and into the crust at and near rifts along the ridge axes. The
crystallized magma forms new crust of basalt (known as MORB for mid-ocean ridge
basalt) and gabbro.

The oceanic crust is made up of rocks much younger than the Earth itself. Most
oceanic crust in the ocean basins is less than 200 million years old. The crust is in a
constant state of "renewal" at the ocean ridges. Moving away from the mid-ocean
ridge, ocean depth progressively increases; the greatest depths are in ocean trenches
Mid-Oceanic Ridge Formation
Vents

A hydrothermal vent is a fissure in a planet's surface from which
geothermal heated water is released/produced.

Hydrothermal vents are commonly found near volcanically active places,
areas where tectonic plates are moving apart, ocean basins, and
hotspots.

Relative to the majority of the deep sea, the areas around submarine
hydrothermal vents are biologically more productive, often hosting
complex communities fueled by the chemicals dissolved in the vent
fluids. Chemosynthetic bacteria and archaea form the base of the food
chain, supporting diverse organisms, including giant tube
worms, clams,limpets and shrimp.
Hydrothermal Vents
Oceanic Trench

Ocean trenches are long, narrow depressions on theseafloor.
These chasms are the deepest parts of the ocean—and some of the
deepest natural spots on Earth. Ocean trenches are found in every
ocean basin on the planet, although the deepest ocean trenches ring
the Pacific as part of the so-called “Ring of Fire” that also includes active
volcanoes and earthquake zones.

Ocean trenches are a result of tectonic activity, which describes the
movement of the Earth’s lithosphere. In particular, ocean trenches are a
feature of convergent plate boundaries, where two or more tectonic
plates meet. At many convergent plate boundaries, dense lithosphere
melts or slides beneath less-dense lithosphere in a process
called subduction, creating a trench.
Oceanic Trench
Underwater Volcanism

Seamount

Island

Island Chain

Guyot (Tablemount)

Atoll
FORMATIONS
https://www.youtube.com/watch?v=D1eibbfAEVk
Seamount

A seamount is a mountain rising from the ocean seafloor that does not
reach to the water's surface (sea level), and thus is not an island.

Seamounts are typically formed from extinct volcanoes that rise abruptly
and are usually found rising from the seafloor to 1,000–4,000 metres (3,300–
13,100 ft) in height.

The biological richness of seamount habitats results from the shape of
these undersea mountains. Thanks to the steep slopes of seamounts,
nutrients are carried upwards from the depths of the oceans toward the
sunlit surface, providing food for creatures ranging from corals to fish to
crustaceans.
Seamount
Island

An island is any piece of sub-continental land that is surrounded
completely by water.

Oceanic islands are ones that do not sit on continental shelves. The vast
majority are volcanic in origin such as Saint Helena in the South Atlantic
Ocean.[11] The few oceanic islands that are not volcanic are tectonic in
origin and arise where plate movements have lifted up the deep ocean
floor to above the surface. Examples of this include Saint Peter and Paul
Rocks in the Atlantic Ocean and Macquarie Island in the Pacific.

One type of volcanic oceanic island is found in a volcanic island arc.
These islands arise from volcanoes where the subduction of one plate
under another is occurring.
Island
Island Chain

Island group or island chain, is a chain, cluster or collection of islands.

May be found isolated in bodies of water or neighboring a large land
mass. For example, Scotland has more than 700 islands surrounding its
mainland which constitute an archipelago. Archipelagos are often
volcanic, forming along island arcs generated by subduction
zones or hotspots, but may also be the result of erosion, deposition,
and land elevation.
Island Chain
ISLAND FORMATION
https://www.youtube.com/watch?v=ZvpZ0pNWxAU
https://www.youtube.com/watch?v=bYv6V5EJAKc
Guyot

A guyot, also known as a tablemount, is an isolated underwater volcanic
mountain (seamount), with a flat top over 200 metres (660 feet) below the
surface of the sea. The diameters of these flat summits can exceed 10 km
(6.2 mi).
Atoll

A ring-shaped reef, island or chain of islands formed of coral

An atoll surrounds a body of water called a lagoon.

Atolls develop with underwater volcanoes, called seamounts.

1) Volcano builds and erupts causing seamount elevation to rise

2) Tiny sea animals called coral build a reef around the island

3) The water between the reef and the island is the lagoon

4) Seamount eroded away over a long time

5) Ocean waves break pieces of limestone reef, erode coral into tiny grains of sand

6) The sand deposited by waves or wind pile up on the reef, the deposits form a ring shaped
island- this is an atoll
Atoll
Costal Features

Peninsula

Delta

Submarine Canyon

Cape

Bay
Peninsula




A piece of land almost surrounded by water or projecting out into a
body of water. (3 sides) Joined to a large area of land
EX: Korean peninsula
Peninsulas are found on every continent. In North America, the narrow
peninsula of Baja California, in Mexico, separates the Pacific Ocean
and the Sea of Cortez, also called the Gulf of California. In Europe, the
nations of Portugal and Spain make up the Iberian Peninsula.
Continental Peninsula
Not all peninsulas are skinny little bits of land. Europe (the whole thing!)
is sometimes considered a large peninsula extending off the single
continent of Eurasia.
Peninsula
Delta

Deltas are wetlands that form as rivers empty their water and sediment into another body of water, such
as an ocean, lake, or another river. Deltas can also empty into land, although this is less common.

A delta is sometimes divided into two parts: subaqueous and subaerial. The subaqueous part of a delta is
underwater. This is the most steeply sloping part of the delta, and contains the finest silt. The newest part
of the subaqueous delta, furthest from the mouth of the river, is called the prodelta.

The subaerial part of a delta is above water. The subaerial region most influenced by waves and tides is
called the lower delta. The region most influenced by the river's flow is called the upper delta.

This nutrient-rich wetland of the upper and lower delta can be an extension of the river bank, or a series
of narrow islands between the river's distributary network.

Like most wetlands, deltas are incredibly diverse and ecologically important ecosystems.
Deltas absorbrunoff from both floods (from rivers) and storms (from lakes or the ocean). Deltas
also filter water as it slowly makes its way through the delta's distributary network. This can reduce the
impact of pollution flowing from upstream.

Deltas are also important wetland habitats. Plants such as lilies and hibiscus grow in deltas, as well
asherbs such as worts, which are used in traditional medicines.
Delta
Submarine Canyon

Steep-sided valley cut into the sea floor of the continental slope, sometimes extending
well on the continental shelf and having relief comparable to even the largest land
canyons.

Submarine canyons are more common on the steep slopes found on active margins compared to
those on the gentler slopes found on passive margins.[4] They show erosion through all substrates,
from unlithifiedsediment to crystalline rock. Canyons are steeper, shorter, more dendritic and more
closely spaced on active than on passive continental margins.The walls are generally very steep
and can be near vertical. The walls are subject to erosion by bioerosion, or slumping. There are an
estimated 9,477 submarine canyons on earth, covering about 11% of the continental slope.

Aviles Canyon, the deepest submarine canyon in the world, southern Bay of Biscay, Spain. Up to
4,750 m from the slope.
Submarine Canyon
Cape

A cape is a high point of land that extends into a river, lake, or ocean. Some capes, such as
the Cape of Good Hope in South Africa, are parts of large landmasses. Others, such as Cape
Hatteras in the U.S. state of North Carolina, are parts of islands.

Capes can be formed through many different processes, including the movement of ocean
currents, rivers, erosion, and glaciers.

Peninsulas are similar to capes. Most geographers consider capes to be smaller than
peninsulas. Capes are narrow features that jut into a body of water. Peninsulas can be large,
and many are barely connected to the mainland at all.

Cape Cod in the U.S. state of Massachusetts, was formed by glaciers. During the last ice age, a
glacier carved its way through the North American landscape. Earthen material
called moraine piled up in front of and on either side of the glacier. As the glacier melted and
retreated, the piles of land emerged as a fishhook-shaped cape.
Cape
Bay

A bay is a body of water connected to an ocean or lake, formed by an indentation of the shoreline. A
large bay may be called a gulf, a sea, a sound, or a bight. A cove is a smaller circular or oval coastal
inlet with a narrow entrance; some coves may be referred to as bays.

There are various ways from which bays can be created. The largest bays have developed as a result
of continental drift.[2] As the super-continent Gondwana broke up along curved and indented fault lines,
the continents moved apart and the world's largest bays formed. These include the Gulf of
Guinea, Persian Gulf, Gulf of Alaska, Gulf of Mexico and the Bay of Bengal, which is the largest bay in the
world.[2]

Another way bays form is via glacial and river erosion. A bay formed by a glacier is a fjord. Rias are
created by rivers and are characterised by more gradual slopes. Most gulf and bays form by
the folding of the earth's crust, and by coastal erosion due to waves and currents. Currents can make
waves more constant, and soft rocks speed erosion. Hard rock eroded less quickly, leaving headlands.
The Gulf of California is an example of a bay created by the geological process of folding.
Bay