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What is Continental Drift and Plate Tectonics?

What is Continental Drift and Plate Tectonics?

Posted by The Science Mall Team on 1st May 2023

Plate tectonics and continental drift is a relatively young science. This story begins only 70 years ago. These sciences are relatively young.  Plate tectonics and continental drift took decades to be approved theories. We still have much to learn about them but here is the short story.

In the 1950s-60s, Marie Tharp and Bruce Heezen revolutionized our understanding of oceanography by discovering the Mid-ocean ridges and rift zones. Their research helped to drastically improve our understanding of the Earth's structure and composition. 

Tharp, an American geologist, and mathematician, is credited with mapping the Mid-ocean ridges. Combining bathymetric data with seismic data provided by Bruce Heezen and some early oceanic research vessel expeditions, Marie Tharp created the first comprehensive map of the underwater mountain ranges that stretched around the world and were found in all five oceans. 

In the 1950s, science was undergoing many new and difficult transitions. Things were still done by hand then, and Marie worked tirelessly with sheer ingenuity and determination to interpret the data. Plotting the peaks, plains, and troughs was all done carefully using the change of slope and raw "fathometer records" to reveal what had never been seen before. No doubt burning midnight oil, the complexity of the ocean floor finally became apparent, and where there were once dots and plots on a graph - revealed abyssal plains and continental rises. This new knowledge presented a big problem, as the words "continental drift" were considered heretical words by most scientists at that time. 

Tharp and Heezen entered a period of tension and anxiety, as their new knowledge would indicate that continental drift was not skewed thinking but accurate. The moment was akin to what Charles Darwin felt when his theory of evolution was finally the only conclusion that made any sense. 

"If there was such a thing as continental drift, it seemed logical that something like a Mid-ocean rift valley might be involved. The valley would form where new material came up from deep inside the Earth, splitting the Mid-ocean ridge in two and pushing the sides apart. That, in turn, would move the continents on their various tectonic plates," Marie wrote. 

The discovery of the Mid-ocean ridges and rift zones provided valuable insight into the structure of Earth's crust. The process of seafloor spreading along these ridges helped create a turnover for the birth of a new oceanic crust. Ridges or rift zones are formed when two plates begin to separate or diverge. Their work revealed that molten magma was being forced through these plates, causing them to split apart. When the magma cooled down, it created a new crust along the rift zone. 

The work of Tharp and Heezen fundamentally changed the way we looked at the Earth and geological processes. Like the seams on a baseball, we now know that the Mid-Ocean ridge system wraps its way around our planet, stretching some 40,000 miles. Mid-ocean ridges form at divergent plate boundaries where tectonic plate spreads produce new oceanic crust. This process causes molten rock to rise to the surface, which leads to massive volcanic eruptions of basalt. In addition, the rate at which plates move apart affects the shape of the ridge. A slower spread results in uneven and steep terrain, while a faster spread creates a wider, gently sloping topography. 

The Mid-Atlantic Ridge and the East Pacific Rise are the only two mid-ocean ridges that have been extensively studied. The Mid-Atlantic Ridge is situated in the middle of the Atlantic Ocean and is gradually widening at a pace of 2 to 5 centimeters (0.8 to 2 inches) per year, creating a rift valley that is similar in depth and width to the Grand Canyon. The East Pacific Rise is spreading faster than the Atlantic, with rates of 6 to 16 centimeters (3 to 6 inches) per year. Although the mid-ocean ridge system is a prominent feature on Earth, much remains a mystery. 

Photo courtesy: by IFE, URI-IAO, UW, Lost City Science Party; NOAA/OAR/OER; The Lost City 2005 Expedition. - NOAA Photo Library: expl2286 Picture information: Basaltic rocks of the Lost City Expedition observed at the Mid-Atlantic Ridge by the Hercules ROV Look up the Lost City hydrothermal vent system in the Atlantic Ocean to dive deeper! This incredible geological wonder will be our topic in the NEXT BLOG!

These blogs help serve as a timeline, showing how far science has come in such a short time.