Question

briefly discuss about the distribution of oceans and continents

Answer 1

In the previous chapter, you have studied the
interior of the earth. You are already familiar
with the world map. You know that continents
cover 29 per cent of the surface of the earth
and the remainder is under oceanic waters.
The positions of the continents and the ocean
bodies, as we see them in the map, have not
been the same in the past. Moreover, it is now
a well-accepted fact that oceans and
continents will not continue to enjoy their
present positions in times to come. If this is
so, the question arises what were their positions
in the past? Why and how do they change their
positions? Even if it is true that the continents
and oceans have changed and are changing
their positions, you may wonder as to how
scientists know this. How have they determined
their earlier positions? You will find the answers
to some of these and related questions in this
chapter.
CONTINENTAL DRIFT
Observe the shape of the coastline of the Atlantic
Ocean. You will be surprised by the symmetry
of the coastlines on either side of the ocean. No
wonder, many scientists thought of this
similarity and considered the possibility of the
two Americas, Europe and Africa, to be once
joined together. From the known records of the
history of science, it was Abraham Ortelius, a
Dutch map maker, who first proposed such a
possibility as early as 1596. Antonio Pellegrini
drew a map showing the three continents together.
However, it was Alfred Wegener—a German
meteorologist who put forth a comprehensive
argument in the form of “the continental drift
DISTRIBUTION OF OCEANS
AND CONTINENTS
CHAPTER
theory” in 1912. This was regarding the
distribution of the oceans and the continents.
According to Wegener, all the continents
formed a single continental mass and mega
ocean surrounded the same. The super
continent was named PANGAEA, which meant
all earth. The mega-ocean was called
PANTHALASSA, meaning all water. He argued
that, around 200 million years ago, the super
continent, Pangaea, began to split. Pangaea first
broke into two large continental masses as
Laurasia and Gondwanaland forming the
northern and southern components
respectively. Subse-quently, Laurasia and
Gondwanaland continued to break into various
smaller continents that exist today. A variety of
evidence was offered in support of the
continental drift. Some of these are given below.
Evidence in Support of the Continental Drift
The Matching of Continents (Jig-Saw-Fit)
The shorelines of Africa and South America
facing each other have a remarkable and
unmistakable match. It may be noted that a
map produced using a computer programme
to find the best fit of the Atlantic margin was
presented by Bullard in 1964. It proved to be
quite perfect. The match was tried at 1,000-
fathom line instead of the present shoreline.
Rocks of Same Age Across the Oceans
The radiometric dating methods developed in
the recent period have facilitated correlating the
rock formation from different continents across