Mid-Ocean Ridge Activity
This activity consists of naming the continents, identifying mid-ocean ridges,
and determining the age of the ocean floor. Once you have labeled each map
correctly, you should be able to answer the series of questions that follow
the exercise.
The final map will allow you to explore all of the maps using a slide scale
located above each tab. Navigating with the slide will provide different views
of the maps, which will help with understanding the relationship between the
continents, mid-ocean ridges and the age of the ocean floor.
Questions
- Where is the youngest ocean floor located?
Check Answer
The youngest ocean floor is located on the mid-ocean
ridge.
- Where is the oldest ocean floor located?
Check Answer
The oldest ocean floor is located near the continents,
next to a subduction zone.
- There are rocks on every continent that are 3 to 4 billion years old. Why
are there no oceanic rocks older than 200 million years?
Check Answer
Oceanic crust is eventually destroyed in subduction
zones. Although oceanic crust has been forming on Earth for over 4 billion
years, all of the sea floor older than about 200 million years has been
recycled by plate tectonics. Continental crust is not subducted and destroyed,
so very old continental rocks have survived.
- In the eastern Pacific, why are oceanic rocks no older than 120 million
years?
Check Answer
The eastern Pacific Mid-Oceanic Ridge is not far
from the subduction zone that runs along the west coast of South America.
The ocean floor spreading eastward is subducted and destroyed relatively
soon after formation.
- Based on the distribution of color on the map, which ridge is spreading
faster, the Mid-Atlantic Ridge or the East Pacific Rise (ridge and rise are
both nicknames for a mid-oceanic ridge)?
Check Answer
The East Pacific Rise is spreading faster than
the Mid-Atlantic Ridge. The wide swath of red and orange parallel to the
East Pacific Rise illustrates that a large area of oceanic rocks are very
young.
- Based on the distribution of color on the map, which ridge is spreading
faster, the Mid-Atlantic Ridge or the Southeast Indian Ridge?
Check Answer
The Southeast Indian Ridge is spreading faster
than the Mid-Atlantic Ridge.
- How does the rate of spreading of the Southeast Indian Ridge compare to
the Southwest Indian Ridge?
Check Answer
The Southeast Indian Ridge is spreading faster
than the Southwest Indian Ridge.
Critical Thinking Question
If the mid-ocean ridges active today continue to produce new sea floor for
another 100-200 million years, how will the appearance and location of oceans
and continents be changed?
Possible Answer
Scientists seek to understand and explain how the natural
world works. Many of the questions raised in this endeavor have no absolute
answers.
The Pacific Ocean will probably disappear, swallowed up by subduction on
its margins. The Atlantic will have widened enormously, pushing North and
South America into Asia, Indonesia, and Australia. This new, giant land mass
will likely be shoved far to the north by the spreading along the ridges
that circle Antarctica, leaving that icy continent nearly alone in the southern
hemisphere.