Journey to the
Bottom of the Ocean
Continental Shelf
The edge of the continents slope down from the
shore into the ocean. The part of the continent
located under water is known as the continental
shelf.
The continental shelf is rich in resources such as
marine life, minerals and oil. For this reason,
countries around the world claim the bordering
continental shelf as part of their territories.
Continental Slope
The continental slope is a steep
slope that connects the continental
shelf to the bottom of the ocean
floor. The slope begins at a depth
of around 460 feet (140 meters).
Seamount
• Seamounts are undersea volcanic
mountains rising from the bottom of the
sea that do not break the water's surface
• Seamounts are usually isolated and
cone-shaped, often volcanic in origin.
Volcanic Island Arc
• Volcanic island arcs are a series of
seamounts tall enough to break the sea
surface and form an island.
• The Augustine Island Volcano in Alaska is
an example of a volcanic arc.
Guyot
• Guyots are seamounts that have risen above sea
level. Over time erosion by waves destroys the top
of the seamount resulting in a flattened shape.
Seamount rises
above water
Erosion by waves
flattens the top of the
mount
The seamount
becomes submerged
to form a guyot
Mid Ocean Ridge
•The mid ocean ridge is a series of mountain ranges on the
ocean floor.
•They are more than 84,000 kilometers (52,000 miles) in
length and they extend through the North and South of the
Atlantic ocean, the Indian Ocean, and the South Pacific
ocean.
•According to the plate tectonics theory, volcanic rock is
added to the sea floor as the mid-ocean ridge spreads
apart.
Rift
• A rift valley is formed
where two tectonic plates
pull apart from one
another creating a deep
valley.
• Rifts are the opposite of
mountain ranges like the
Alps or the Himalayas
where the plates push
together to create a
mountain.
Ocean Trench
• An ocean 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.
• They reach depths of nearly 7 mi (10 km) below sea
level.
• They can be thousands of miles in length, yet as little
as 5 mi (8 km) in width.
Abyss
• The deepest point in the
ocean is called the abyss
• The Mariana Trench is the
deepest known point in the
ocean. It is located in the
western part of the Pacific
Ocean near the fourteen
Mariana Islands.
Abyssal Plain
Abyssal plains are the vast, flat,
sediment-covered areas of the deep
ocean floor. They are the flattest, most
featureless areas on Earth. These flat
abyssal plains occur at depths of over
6,500 ft (1,980 m) below sea level.
Compare continental and
oceanic landforms
Continental landform
Oceanic landform
Canyon
Trench
Valley
Rift
Volcanic mountain
Seamount
Mountain Range
Mid-ocean ridge
Low hills or plains
Ocean basin (abyssal plains)