What was ewing’s evidence for continental drift

The rest of us were working on this little problem and that little problem, and Lamont had the whole view. Climate , Earth Sciences. Notify of. I agree to help cultivate an open and respectful discussion. Inline Feedbacks. Would love your thoughts, please comment. Poorly respected in his lifetime, Wegener and his ideas about moving continents seemed destined to be lost in history as fringe science. However, in the s, evidence started to trickle in that made continental drift a more viable idea.

Ongoing GPS and earthquake data analyses continue to support this theory. In researchers started using an adaptation of SONAR to map a region in the middle of the Atlantic Ocean with poorly-understood topographic and thermal properties [ 9 ]. Using this information, Bruce Heezen and Marie Tharp created the first detailed map of the ocean floor to reveal the Mid-Atlantic Ridge [ 10 ], a basaltic mountain range that spanned the length of the Atlantic Ocean, with rock chemistry and dimensions unlike the mountains found on the continents.

Initially, scientists thought the ridge was part of a mechanism that explained the expanding Earth or ocean-basin growth hypotheses [ 11 ; 12 ].

In , Harry Hess proposed the hypothesis of seafloor spreading — that the mid-ocean ridges represented tectonic plate factories, where a new oceanic plate was issuing from these long volcanic ridges. Scientists later included transform faults perpendicular to the ridges to better account for varying rates of movement between the newly formed plates [ 13 ].

When earthquake epicenters were discovered along the ridges, the idea that earthquakes were linked to plate movement took hold [ 14 ]. Seafloor sediment, measured by dredging and drilling, provided another clue. Scientists once believed sediment accumulated on the ocean floors over a very long time in a static environment.

When some studies showed less sediment than expected, these results were initially used to argue against the continental movement [ 15 ; 16 ]. With more time, researchers discovered these thinner sediment layers were located close to mid-ocean ridges, indicating the ridges were younger than the surrounding ocean floor. This finding supported the idea that the seafloor was not fixed in one place [ 17 ]. The seafloor was also mapped magnetically. Scientists had long known of strange magnetic anomalies that formed a striped pattern of symmetrical rows on both sides of mid-oceanic ridges.

What made these features unusual was the north and south magnetic poles within each stripe was reversed in alternating rows [ 18 ]. By , Harry Hess and other scientists used these magnetic reversal patterns to support their model for seafloor spreading [ 19 ] see also Lawrence W. Morley [ 20 ]. Paleomagnetism is the study of magnetic fields frozen within rocks, basically a fossilized compass. In fact, the first hard evidence to support plate motion came from paleomagnetism.

Igneous rocks containing magnetic minerals like magnetite typically provide the most useful data. When the rock cools and solidifies, this alignment is frozen into place, creating a permanent paleomagnetic record that includes magnetic inclination related to global latitude, and declination related to magnetic north.

Some explained this as part of the normal movement of earth magnetic north pole. Eventually, scientists realized adding the idea of continental movement explained the data better than the pole movement alone [ 21 ]. Around the same time mid-ocean ridges were being investigated, other scientists linked the creation of ocean trenches and island arcs to seismic activity and tectonic plate movement [ 22 ].

Several independent research groups recognized earthquake epicenters traced the shapes of oceanic plates sinking into the mantle. These deep earthquake zones congregated in planes that started near the surface around ocean trenches and angled beneath the continents and island arcs [ 23 ]. Department of Agriculture would inherit a taste for both geology and cartography.

Like many other women scientists of her day, Tharp found an unexpected opportunity in the form of a world war. Tharp knew that geology was a long shot. Women were not recognized by some professional societies and had long been discouraged from working in the field. But field studies are at the core, as it were, of much geology research.

At the time, it was good advice—women who refused to perform the deskbound of analyzing and drawing out results collected by men rarely found work in the sciences. Luckily for Tharp, the seemingly low-level drafting skills she honed would later lead to the biggest discovery of her career.

Called the Lamont-Doherty Earth Observatory today, the lab was ground zero for cutting-edge earth sciences research. It was a heady time for the field, in large part because it was so untapped. Meteorologist Alfred Wegener, fueled in part by observations of how South America and Africa had coastlines that looked like they went together and the existence of similar fossils in extremely different parts of the world, had proposed the concept of continental drift back in the nineteen-teens.

It is now called the Mid-Ocean Ridge. In , American physicists Maurice Ewing and Bruce Heezen discovered that through this underwater mountain range ran a deep canyon. In some places the canyon, called the Great Global Rift, came very close to land.

The rift appeared to be breaks in the earth's crust, but perfectly fitted breaks, like joints made by a carpenter. The rift outlined chunks of the earth's crust, which were named tectonic from a Greek word for "carpenter" plates.