Getting Geographic:
Exploring Landscapes Beneath the Oceans
Earth’s continental landscapes – mountains,
valleys, canyons – are familiar to students
everywhere. But many students do not realize
that ocean floor landscapes are equally
dramatic and varied.
Martha’s Study Corner
September 21, 2010
Vol. 1: #2
Features on the Ocean Floor
In the map (upper right), which uses a
technique called “choropleth mapping” to
show depth, areas of darkest blue are the
deepest parts of the oceans, while areas of
light blue are relatively shallow.
Oceans cover approximately 71% of Earth’s
surface. Their average depth is 16,000 feet
(4,880 meters). But the ocean floor is marked
by mountain chains called “mid-ocean ridges”
and deep valleys called “trenches.”
Mapping the Ocean Floor Landscape
Provide students with blank world maps.
(A world outline map can be downloaded
from:
http://www.nationalgeographic.com/xpeditions
/atlas/world/world-d.pdf)
Have students use National Geographic
ocean floor maps available at:
http://maps.nationalgeographic.com/maps/atla
s/pacific-ocean-geophysical.html to locate and
label the following ocean floor features on
their outline maps.
Pacific Ocean – Mariana Trench (-35, 827 ft/
-10,920 m.); Japan Trench (-34,318 ft/-10,375
m.); East Pacific Rise (under water ridge)
Atlantic Ocean – Puerto Rico Trench (28,231 ft./-8,605 m.); Brazil Basin (-20,898 ft./6,310 m.); Mid-Atlantic Ridge
Indian Ocean – Java Trench (-23,812 ft./
-7,258 m.); Mid-Indian Ocean Ridge
Arctic Ocean – Fram Basin (-15,305 ft./4,665 m.); Lomonosov Ridge
Extension Activity
In 2000, the International Hydrographic
Organization identified a fifth division in
Earth’s oceans—sometimes called the
Southern Ocean. This ocean area, which
extends from the shores of Antarctica to 60º
South latitude, is not universally recognized as
a separate ocean. Have students research
the so-called Southern Ocean and identify its
unique characteristics.