Continental Drift Hypothesis



Continental drift is the movement of the Earth's continents relative to each other. The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912 when he noticed that the shapes of continents on either side of the Atlantic Ocean seem to fit together (for example, Africa and South America). Francis Bacon, Antonio Snider-Pellegrini, Benjamin Franklin, and others had noted much the same thing earlier. However, it was not until the development of the theory of plate tectonics in the 1960s, that a sufficient geological explanation of that movement was found.

The similarity of southern continent fossil faunas and some geological formations had led a relatively small number of Southern hemisphere geologists to conjecture as early as 1900 that all the continents had once been joined into a supercontinent known as Pangaea.

The concept was initially ridiculed by most geologists, who felt that an explanation of how a continent drifted was a prerequisite and that the lack of one made the idea of drifting continents wholly unreasonable.

The theory received support through the controversial years from South African geologist Alexander Du Toit as well as from Arthur Holmes. The idea of continental drift did not become widely accepted as theory until the 1950s in Europe.

By the 1960s, geological research conducted by Robert Dietz, Bruce Heezen, and Harry Hess along with a rekindling of the theory including a mechanism by J. Tuzo Wilson led to acceptance among North American geologists.

The hypothesis of continental drift became part of the larger theory of plate tectonics. This article deals mainly with the historical development of the continental drift hypothesis before 1950.

Evidence for the movement of continents on tectonic plates is now extensive. Similar plant and animal fossils are found around the shores of different continents, suggesting that they were once joined. The fossils of Mesosaurus, a freshwater reptile rather like a small crocodile, found both in Brazil and South Africa, are one example; another is the discovery of fossils of the land reptile Lystrosaurus in rocks of the same age at locations in Africa, India, and Antarctica. There is also living evidence the same animals being found on two continents. Some earthworm families (e.g. Ocnerodrilidae, Acanthodrilidae, Octochaetidae) are found in South America and Africa, for instance.

The complementary arrangement of the facing sides of South America and Africa is obvious, but is a temporary coincidence. In millions of years, slab pull and ridge-push, and other forces of tectonophysics, will further separate and rotate those two continents. It was this temporary feature which inspired Wegener to study what he defined as continental drift, although he did not live to see his hypothesis generally accepted.

Widespread distribution of Permo-Carboniferous glacial sediments in South America, Africa, Madagascar, Arabia, India, Antarctica and Australia was one of the major pieces of evidence for the theory of continental drift. The continuity of glaciers, inferred from oriented glacial striations and deposits called tillites, suggested the existence of the supercontinent of Gondwana, which became a central element of the concept of continental drift. Striations indicated glacial flow away from the equator and toward the poles, based on continents' current positions and orientations, and supported the idea that the southern continents had previously been in dramatically different locations, as well as being contiguous with each other. Continental Drift Hypothesis




Development of Tectonophysics

The evolution of tectonophysics is closely linked to the history of the continental drift and plate tectonics hypotheses. The continental drift hypothesis had many flaws and scarce data. The fixist, the contracting Earth and the expanding Earth concepts had many flaws as well. Wegener had data for assuming that the relative positions of the continents change over time. It was a mistake to state the continents "plowed" through the sea.

He was an outsider with a doctorate in astronomy attacking a established theory between geophysicists. The geophysicists were right to state that the Earth is solid, and the mantle is elastic (for seismic waves) and inhomogeneous, and the ocean floor would not allow the movement of the continents.

But excluding one alternative, substantiates the opposite alternative: passive continents and an active seafloor spreading and subduction, with accretion belts on the edges of the continents. The velocity of the sliding continents, was allowed in the uncertainty of the fixed continent model and seafloor subduction and upwelling with phase change allows for inhomogeneity.

The problem too, was the specialization. A. Holmes and A. Rittmann saw it right (Rittmann 1939). Only an outsider can have the overview, only an outsider sees the forest, not only the trees (Hellman 1998b, p. 145). But A. Wegener did not have the specialization to correctly weight the quality of the geophysical data and the paleontologic data, and its conclusions. Wegener's main interest was meteorology, and he wanted to join the Denmark-Greenland expedition scheduled for mid 1912. So he hurried up to present his Continental Drift hypothesis.

Timeline of the Development of Tectonophysics




The Great Rift Valley

The Great Rift Valley is a name given in the late 19th century by British explorer John Walter Gregory to the continuous geographic trench, approximately 6,000 kilometres (3,700 mi) in length, that runs from northern Syria in Southwest Asia to central Mozambique in East Africa.

The name continues in some usages, although it is today considered geologically imprecise as it combines features that are today regarded as separate, although related, rift and fault systems.

Today, the term is most often used to refer to the valley of the East African Rift, the divergent plate boundary which extends from the Afar Triple Junction southward across eastern Africa, and is in the process of splitting the African Plate into two new separate plates. Geologists generally refer to these incipient plates as the Nubian Plate and the Somali Plate.

The Great Rift Valley




In the News





The African continent is very slowly peeling apart. Scientists say a new ocean is being born   NBC - July 19, 2020
In one of the hottest places on Earth, along an arid stretch of East AfricaŐs Afar region, itŐs possible to stand on the exact spot where, deep underground, the continent is splitting apart. This desolate expanse sits atop the juncture of three tectonic plates that are very slowly peeling away from each other, a complex geological process that scientists say will eventually cleave Africa in two and create a new ocean basin millions of years from now. For now, the most obvious evidence is a 35-mile-long crack in the Ethiopian desert.




Maps reveal new details about New Zealand's lost underwater continent   CNN - June 23, 2020

Under New Zealand, there lies a vast continent on the sea floor. Once part of the same land mass as Antarctica and Australia, the lost continent of Zealandia broke off 85 million years ago and eventually sank below the ocean, where it stayed largely hidden for centuries. Now, maps reveal new research about the underwater continent where dinosaurs once roamed - and allow the public to virtually explore it. GNS Science, a New Zealand research institute, published two new maps and an interactive website on Monday. The maps cover the shape of the ocean floor and Zealandia's tectonic profile, which collectively help tell the story of the continent's origins.




The lost continent of Zealandia hides clues to the Ring of Fire's birth   Live Science - February 11, 2020
The hidden undersea continent of Zealandia underwent an upheaval at the time of the birth of the Pacific Ring of Fire. Zealandia is a chunk of continental crust next door to Australia. It's almost entirely beneath the ocean, with the exception of a few protrusions, like New Zealand and New Caledonia. But despite its undersea status, Zealandia is not made of magnesium- and iron-rich oceanic crust. Instead, it is composed of less-dense continental crust. The existence of this odd geology has been known since the 1970s, but only more recently has Zealandia been more closely explored. In 2017, geoscientists reported in the journal GSA Today that Zealandia qualifies as a continent in its own right, thanks to its structure and its clear separation from the Australian continent.




Diamond samples in Canada reveal size of lost continent   BBC - March 21, 2020
Canadian scientists have discovered a fragment of an ancient continent, suggesting that it was 10% larger than previously thought. They were studying diamond samples from Baffin Island, a glacier-covered land mass near Greenland, when they noticed a remnant of North Atlantic Craton. Cratons are ancient, stable parts of the Earth's continental crust. The North American Craton stretched from present-day Scotland to North America and broke apart 150m years ago. Scientists chanced on the latest evidence as they examined exploration samples of kimberlite, a rock that often contains diamonds, from Baffin Island.




Geologists find lost fragment of ancient continent in Canada's North   PhysOrg - March 20, 2020

Sifting through diamond exploration samples from Baffin Island, Canadian scientists have identified a new remnant of the North Atlantic craton - an ancient part of Earth's continental crust. A chance discovery by geologists poring over diamond exploration samples has led to a major scientific payoff. Kimberlite rock samples are a mainstay of diamond exploration. Formed millions of years ago at depths of 150 to 400 kilometers, kimberlites are brought to the surface by geological and chemical forces. Sometimes, the igneous rocks carry diamonds embedded within them. The newly identified fragment covers the diamond bearing Chidliak kimberlite province in southern Baffin Island. It adds roughly 10 percent to the known expanse of the North Atlantic craton.




What are lost continents, and why are we discovering so many? In the past few years, we've seen an increase in the discovery of lost continents   PhysOrg - November 25, 2019

For most people, continents are Earth's seven main large landmasses. But geoscientists have a different take on this. They look at the type of rock a feature is made of, rather than how much of its surface is above sea level. In the past few years, we've seen an increase in the discovery of lost continents. Most of these have been plateaus or mountains made of continental crust hidden from our view, below sea level. One example is Zealandia, the world's eighth continent that extends underwater from New Zealand. Several smaller lost continents, called microcontinents, have also recently been discovered submerged in the eastern and western Indian Ocean




Andes - Birthplace of Earth's Continents Discovered Under These Mountains   Live Science - January 31, 2019
Earth's continents may have been born under large mountain ranges like the Andes. New research combining a mysterious missing trace element, a 66-million-year-old rock burped up by an ancient volcano, and a database of all the rock chemistry analyzed by scientists in the past century explains why Earth has continents. A study suggests that where mountains are born, so are continents.




How Earth's continents have shifted: Interactive map lets you travel back in time to see our planet over 600 million years of its history   Daily Mail - May 4, 2018

A new interactive map lets you travel back in time to view our planet as it appeared millions of years ago. 'Ancient Earth Globe' reveals how the continents have split and reformed while oceans advanced and receded across 600 million years of the planet's history.




Big crack is evidence that East Africa could be splitting in two   CNN - April 5, 2018

A large crack, stretching several kilometres, made a sudden appearance recently in south-western Kenya. The tear, which continues to grow, caused part of the Nairobi-Narok highway to collapse and was accompanied by seismic activity in the area. The Earth is an ever-changing planet, even though in some respects change might be almost unnoticeable to us. Plate tectonics is a good example of this. But every now and again something dramatic happens and leads to renewed questions about the African continent splitting in two. The Earth's lithosphere (formed by the crust and the upper part of the mantle) is broken up into a number of tectonic plates. These plates are not static, but move relative to each other at varying speeds, "gliding" over a viscous asthenosphere.




Breakup of supercontinent Pangea cooled mantle and thinned crust   PhysOrg - December 13, 2016

The oceanic crust produced by the Earth today is significantly thinner than crust made 170 million years ago during the time of the supercontinent Pangea. The thinning is related to the cooling of Earth's interior prompted by the splitting of the supercontinent Pangaea, which broke up into the continents that we have today. The mantle is the very hot, but mostly solid, layer of rock between the Earth's crust and core. Magma from the mantle forms oceanic crust when it rises from the mantle to the surface at spreading centers and cools into the rock that forms the very bottom of the seafloor. Since about 2.5 billion years ago, the mantle has been cooling - a phenomenon that doesn't influence the climate on the surface of the Earth and has nothing to do with the issue of short-term man-made climate change.




Secrets of ocean birth laid bare   BBC - July 20, 2006
The largest tear in the Earth's crust seen in decades, if not centuries, could carve out a new ocean in Africa, according to satellite data. Geologists say a crack that opened up last year may eventually reach the Red Sea, isolating much of Ethiopia and Eritrea from the rest of Africa. The 60km-long rift was initially sparked by an earthquake in September. Follow-up observations reported in the journal Nature suggest the split is growing at an unprecedented rate.




How Did Continents Split? Geology Study Shows New Picture   PhysOrg - May 24, 2006
Like pieces in a giant jigsaw puzzle, continents have split, drifted and merged again many times throughout Earth's history, but geologists haven't understood the mechanism behind the moves. A new study now offers evidence that continents sometimes break along preexisting lines of weakness created when small chunks of land attach to a larger continent.





PLATE TECTONICS


GEOLOGY


CRUSTAL DISPLACEMENT


EARTH'S ENERGY GRIDS


POLE SHIFTS


EARTH'S MAGNETIC FIELDS


PACIFIC RING OF FIRE


VOLCANO INDEX


EARTHQUAKES


EARTH CHANGES


PLANET EARTH INDEX


PHYSICAL SCIENCES INDEX


ALPHABETICAL INDEX OF ALL FILES


CRYSTALINKS MAIN PAGE


PSYCHIC READING WITH ELLIE


2012 THE ALCHEMY OF TIME