In 1912 a German meteorologist named Alfred Wegener proposed a theory about how the Earth's
land masses formed.
He suggested that the great continents of the Earth had once formed a single landmass
called Pangea,
which had broken up and drifted apart over time.
He called this process continental drift
and it went against all conventional thinking of the time,
making him very unpopular amongst his peers.
It's a shame because he was absolutely right.
But it would take the work of a young cartographer called Marie Tharp to help turn the tide of
opposition,
leading to one of the greatest paradigm shifts in the earth sciences.
and it all began at the bottom of the ocean.
Marie's father worked for the Department of Agriculture and from a young age, she would
join him on his work trips
as he travelled around the country collecting samples for soil survey maps.
These early experiences were formative in developing Marie's interest in geology
and after gaining a Master's degree in the subject she landed a position at Columbia
University in 1947.
Here she worked as an assistant to Bruce Heezen,
a geology graduate who was collecting thousands of depth measurements across the Atlantic
ocean.
During expeditions Heezen and his team used echo sounding to collect depth data,
which involved sending out high frequency sounds or 'pings'
and recording the time delay of the returning echo.
This data could then be plotted to build a profile of the terrain below.
Unfortunately for Tharp, women were prohibited from joining these early expeditions because
of a fear that they'd bring bad luck at sea.
Instead, she remained behind at the University to process the data,
converting endless rows of depth measurements into detailed profiles of the ocean floor.
Conventional thinking had once believed that the ocean floors were flat, featureless plains,
but Tharp's maps were beginning to tell an entirely different story.
Her profiles revealed the existence of a complex geography of crevices and valleys,
but perhaps most startling was the emergence of a long, V-shaped cleft that ran through
each of her profiles.
These so-called rift-valleys offered support for Wegener's continental drift theory:
If two land masses were moving apart, they'd split the ocean floor in two,
tearing a scar in the landscape and forming a valley below.
Was this evidence for the controversial theory?
Tharp believed so, but Heezen was skeptical, dismissing many of her suggestions as 'girl talk'.
Nevertheless, Tharp was convinced by her findings and later produced a more detailed physiographic
map to further support her case.
At the same time, another graduate student, Howard Foster, was plotting the epicentres
of earthquakes in the same region of the Atlantic.
Tharp noticed that they occurred at the same location as her proposed valley
and as they expanded to other areas, they found something interesting:
where there were mid-oceanic ridges, there were also earthquakes,
so it seemed as though these two were related.
At this point, even the skeptical Heezen could no longer deny what they were looking at:
- a pattern of scars that spanned the Earth's oceans,
permanent wounds torn into existence through the process of continental drift.
The findings were finally reported in 1957, but opposition from the scientific community
was still fierce.
Renowned explorer Jacques Cousteau was so sure they were wrong,
he charted an expedition to film the ocean floor to settle the score once and for all.
But the footage he brought back did the opposite.
It showed the deep valley, it showed how it split the mid-atlantic ridge in half
and it showed that Tharp's maps were right all along.
It was exactly where she had plotted it.
As the evidence mounted, a paradigm shift in the Earth sciences was inevitable.
Tharp's steadfast determination had paved the way for Wegener's continental drift
theory to gain traction.
As as the tide of opposition waned, it gave birth to our modern understanding of plate
tectonics
and secured Tharp's position as one of the most outstanding cartographers of the 20th
century.