The contribution of Alfred Wegener
William C. McCullough
LAIS 370 History of Science
Colorado School of Mines
Abstract
This paper discusses the role of Alfred Wegener in the discovery of the Plates tectonics theory. It is believed that the modern day plate tectonics theory is an advancement of continental drift theory which was discovered by Wegener. The study will seek to explore his efforts and contribution to modern science and how he has helped to shape the world.
Overview
Plate tectonics also known as continental drift theory describes that the earth was at one time many years back a super continent whereby all continents were joined together. However, due to rotation, the continents began drifting apart slowly over years. Evidence from Wegener and other scientists such as Dr. Hess and others contributed largely to development of this theory. The theory further explains why natural disasters happen and geological features of the earth.
Introduction
Alfred Lothar Wegener is known for his contribution in meteorology as well as recognized for pioneering polar research. Further, he is well recognized for advancing the theory of continental drift in 1912. In the continental drift theory, Wegener hypothesized that continents slowly drift around the earth. However, his hypothesis was not accepted since it was controversial until 1950s. This was after numerous discoveries evidenced continental drift such as palaeomagnetism. The continental drift theory provides a substantial basis for the modern model of Plate tectonics.
Brief history
Born in November, 1880 in a family of evangelical minister, Alfred Wegener attended school in Berlin. He later studied physics, astronomy and meteorology in Berlin. In his early works he served as an assistant astronomical observatory. He got a doctorate in Astronomy in 1905 at the Friedrich Wilhelms University currently known as Humboldt University. Throughout this time, Wegener had maintained interest in developing fields of climatology and meteorology. After graduating, he became an assistant at AeronautischenObservatoriumLindenberg. Here, he worked with Kurt his brother who was his senior. Kurt also had interest in science specializing in polar science and meteorology. Together with his brother, they pioneered the weather balloon used to track air masses. In 1906, he participated in Greenland expedition led by Dane Ludvig. He was charged with investigating the last unknown portion of the Greenland’s northeastern coast. He married Elsa Koppen in 1913 and succeeded her father as the director of Meteorological Research Department in 1924. Further, in his adventurers career, Wegener made three expeditions to Greenland whereby he unfortunately died leading his third expedition.
Plate tectonics theory:
According to Stern (2007) plate tectonics is the earth’s horizontal motion boundary layer also known as lithosphere over asthenosphere (mantle) and is driven by lithosphere sinking (Stern R.J). It describes how lithospheric sectors move as well as interact across the earth. The theory was formulated without prior knowledge of what drives the plates. Later studies established that the plates are powered by sinking of the oceanic lithosphere in the subduction zones. Beneath the interior of oceanic plate, the mantle moves towards the ridge while around the plate margins the mantle flows into or away of the basin depending whether the ocean is shrinking or growing.
Wegener’s contribution to plate tectonics
Alfred Wegener, a brilliant scientist and polymath, to the creation of his hypothesis came somewhat by accident. First time when he came up with the idea of moving continents was while studying the map of the world, he was struck by the similarity coast shapes on both sides of the Atlantic. This prompted him to review the results of geological and paleontological studies that are relevant to this issue.
Wegener can be termed as the father of Plate tectonics because of his vast contribution in continental drift theory which is the modern plate tectonics theory. In his theory, the Earth’s continents were once joined together but gradually moved apart for over millions of years. He noted that the East coast of South America lined up almost perfectly with the west coast of Africa. However, this was not new observation as it had already been established in 1620 by Francis Bacon. In 1858, there was a suggestion by Antonio Snider that the biblical flood had moved the continents (Stern R.J). However, most people observed the apparent similarities of the two coasts. Nonetheless, Wegener used geological evidence to support his claim that South America and Africa were once connected. He used a collection of maps, fossil record and rock formations to provide evidence of the connection. He was the first to look into how the continents fit together. Wegener applied shelve technique whereby the continental shelf is the shallow ocean lying of the coast of a continent. He further compared the outlines of the South America’s eastern shelf with the Africa’s west shelf. The continental shelves turned out to fit together better than observable coastlines. The next step was achieved using fossils and geologic records to substantiate his claims. Using fossils, Wegener observed that a small lizard from Paleozoic Era appeared only in two places on Earth: southern Africa and east south of America. The fossils of Mesosaurus which was a fresh water animal and one that is incapable of crossing the Atlantic Ocean provides in one provides reasonable evidence that the two continents were once joined over 270 million years ago.
The Earth at one time was formed in a molten state. For this reason, the heavy elements sunk to the core while the lighter objects floated on the surface. When it cooled, they formed the crust. However, during the cooling, the earth shrunk causing mountains and ocean formation. The earth formation theory was the one that bore headache for Wegener. He discredited the hypothesis on the grounds that the valleys and mountains do not form in uniform pattern. Further, he observed that the Earth crust has two elevations: the continental crust and the ocean abyss. This observation would be pivotal point of study for future scientists. Also, it contributed to theories of floor spreading and plate tectonic theory.
Other people who contributed to plate tectonics
Dr. Hess discovered features that appeared to be mountains with tops flattened on the floor of the ocean. He reexamined data collected at the sea and explained the mechanism behind Wegener’s continental drift theory. Hess published History of Ocean Basins in 1962 describing how hot magma would rise from under the crust and when magma cooled it expanded and pushed the tectonics plates apart. (Harry Hess) New crust was created as a result and pushed under the continental crust.
Plate tectonics and the scientific method
The hypothesis of continental drift has existed for a long time, the hypothesis movement of continents over the Earth's geological history. The establisher of the mobilistic hypothesis is Abbe F. Place, in 1658 he suggested that the Old and the New World had been once represented as a continent that split after the flood.In 1858, the Italian scientist Antonio Cinder-Pelligrinijustified the split of Africa and South America, according to the similarity of coastlines, as well as the similarity of coal deposits and fauna.
Later mobilistic hypothesis was developed by F. Taylor, who published their findings in 1908. In its most complete form mobilistic hypothesis was formulated by the German geophysicist Alfred Wegener. As Synder-Pelligrini, Alfred Wegener was based on data from comprehensive research on the geography, geology and biology, spend the mindifferent part so ftheEarth; Wegener's conclusions were more deep and justified.
Prior to the beginning of the XX century in geology dominated contraction hypothesis: the Earth is cooling down, like baked apples, and wrinkles appear on the continents of mountain ranges. Upon compression of the Earth in the oceans hollows there are tangential forces appearing, which put pressure on continents.In the early twenties of the 20th century, Alfred Wegener came up with the hypothesis of continental drift of the Earth – continents moving through the dense underlying surface. This hypothesis assumed the existence of a single continent in some distant past. It was based on solid data from the fields of geology, geophysics, paleontology, climatology.
Plate tectonics represents a shift in scientific paradigm. Originating from Alfred Wegener, the theory is a perfect example of application of scientific method. (Gurnis M. and Mueller R.D.) The prevailing observation is that continents had always had the same position on the planet as it is today. Such is a very logical view. Nonetheless, Wegener provided convincing evidence stating that over geological time, continents moved across the surface of the earth using radical view. He applied the following steps to solidify his theory:
- Observation
- Research question
- Hypothesis
- Prediction
- Evidence
- Theory
Wegener and his innovative concept immediately became in the middle of attention of the European and the global scientific community which was recovering from the horror of the First World War. Two conferences in Berlin, several reports in Denmark and England.
However, the most important step in the scientific method is the development of a testable hypothesis that provides definitive evidence that the proposed relationships are either right or wrong.Wegener's hypothesis was large enough to cause not only the interest and sympathy, but also the strongest resistance – this is normal in science. After many discussions of twenties - thirties, it was found that in Europe and in North America, scientists - geologists and geophysicists - have remained in positions of Wegener's opponents. At the same time, scientists in South America, South Africa and Australia were his supporters: the geological features of these regions pushed them to the hypothesis of continental drift. It is interesting to consider how long plate tectonics revolution took. Wegener proposed the origin of continents and oceans in 1915 whereby he mentioned out the circumstantial evidence that continents had once been joined yet his plate tectonics theory was not accepted until 1968.
This was after the science of palaeomagnetism which provided data in favor of Wegener’s theory. Early in 1953, samples taken from India ascertained Wegener’s theory because they showed that the country had been previously in the southern hemisphere. Additionally, several developments in geology that led to discovery of spreading of seafloors and Wadati-Benioff zones ascertained the continental drift theory.
- Observation: The Coast of South America and the Coast of Africa fit together like the pieces of a puzzle.
- Problem statement: Why do they fit together?
- Hypothesis: It is possible they were part of a larger continent many years back and have split somehow.
- Prediction: if the continents were connected, then the geology at the corresponding positions in the coasts should correlate
- Evidence: after experimentation in Africa and South America, Wegener found out that rock sequences correlated, Paleo climates are correlated, index fossils are correlated and geologic structures are correlated.
- Theory: the continental drift theory states that parts of the Earth’s crust slowly drift atop a liquid core. Once, all the continents were joined in a super continent often referred as Pangaea by scientists. However, over vast amount of time, the continents drifted apart to their current locations.
Continent drift was caused by earth rotation. The earth was cooling and in the processes it was contracting causing the sea levels to rise and cover the land bridges as per the theory. The theory of plate tectonics implying plate structure was formulated in the 1960s which explains the movement of the earth’s plates and explains the causes of earthquakes oceanic trenches, volcanoes and other geologic formations. There are seven major plates. Each continent sits on its own plate. Australia and India are on the same plate. Most of the pacific is a single plate with no continent. The plates are moving at a speed of 1 to 10 centimeters per year. Moreover, most of the earth’s seismic activity happens at the plate boundaries as they interact. Under the theory, top layers of the plate are referred to as the crust. The crust under the oceans is denser and thinner than continental crust. Similarly, continental crust is less active than oceanic crust whereby the crust is constantly being created and destroyed. There are various types of plate movements as explained by plate tectonics theory. At the boundaries of the plates, there is occurrence of various deformations as the plates interact. The plates separate from one another, collide and slip past one another. When they separate, they cause seafloor spreading. When they collide, they forma mountain ranges and when the plates slip past one another they lead to formation of subduction zones where the plates undergo destruction and re-melting. Also, as explained in plate tectonics theory, the seafloor spreading results in formation of new oceanic crust along a mid-ocean ridge. The plates move away from each other and the region where they are moving away is referred to as zone of divergence. The ocean floor spreading was initially suggested in 1960 by Robert Dietz and Harry Hess. On the contrary, when two plates collide they cause the plates to become smaller and some crust is destroyed. The results are not constant and they depend on the types of plates involved. For instance, when oceanic and continental plates collide, the oceanic plate is forced under the continental plate. This is because the oceanic plate is thin and dense while the continental plate is thick and light hence the denser plate goes down while the light plate remains on surface. This phenomenon is known as subduction. When two continental plates collide crust is compressed and pushed upwards leading to formation of mountain ranges. However, when two oceanic plates collide, one may be pushed under the other depending on which is denser than the other causing magma from the mantle to raise hence formation of volcanoes.
Before development of continental drift theory, it was thought that mountains formed because of contraction caused by the earth when it was cooling down. This was believed to cause wrinkles in the earth’s crust. However, if the hypothesis was correct then we would be having formations all over the earth’s surface.
Evidence used by continental drift theory as applied in plate tectonics theory
Wegener observed that the Western outline of Africa fit the eastern outline of South America. He also noted similar fits among other continents. His theory is backed up by geologists, paleontologists and scientists who have matched misplaced rocks and uncovered fossils and discovered astounding changes in climatology. Fossil remains of prehistoric Mesosasurus have been discovered on both sides of South Atlantic. Plant fossils were also discovered which indicate that tropical forests once existed a few miles from the North Pole. Further, glacial sediments were found in sub-tropical areas. As evidenced by matching sedimentary rock formation between continents, coal seams were uncovered. Wegener theorized that a single super continent once existed during the late Paleozoic era which is roughly 350 million to 220 million years ago. In his theory, he maintained that land masses broke up and pieces drifted and dispersed, eventually stopping at their current position.
According to continental drift theory, the world was made of a single continent which drifted as explained above. According to plate tectonics theory, the earth’s surface is broken into pieces of slabs known as plates which are 50 miles in thickness. The plates move relative to one another above a deeper, hotter and more mobile zone as an average rate of 1 to 10 centimeters per year. In the theory, the most active volcanoes are located along the boundaries between shifting plates. In Wegener’s theory, these boundaries were once joined but separated. The peripheral areas of Pacific Ocean basin contain the boundaries of several plates. Currently, the continental and oceanic plates include Australian-Indian plate, Eurasian plate, Philippine plate, Juan de Fuca plate, pacific plate, North American plates, Nazca plate, Arabian plate, South American plate, Caribbean plate and Antarctic plate. The plates further comprise smaller sub-plates. The earth’s crust became solid billions of years past and therefore its plates have been drifting over the globe. This explains why the earth’s map is constantly changing whereby not only the locations of plates are changing but also the sizes of the plates.
The roots of modern Science are based on man’s eternal quest to comprehend the phenomenon surrounding him. This is achieved through systematic and consistent observations that gradually lead to many discoveries and inventions that have changed the way we think and how we view the modern world. (Pearce and Cann) Plate tectonics is among the discoveries that have completely revolutionized the way people perceive the planet earth. Plate tectonics theory is credited to Germany’s Alfred Lothar who proposed the idea of continental drift that set the basis for the development of plate tectonics theory. Wegener rejected the unrealistic concept of sunken land bridges and presented his theory which was rejected later to be accepted. As it happens in realm science, any radical idea is bound for rejection as it cannot gain immediate acceptance regardless of its merits. According to Albert Einstein, great spirits have always faced stiff opposition from mediocre minds. Wegener’s theory sparked controversy across the world and outranged many scientists hence was not well received. However, according to the new theory, the current day continents are formed from a large monolithic landmass that existed in a distant geological past. His idea was embraced in plate tectonics theory where the earth’s surface is divided into huge seven plates which are constantly moving relative to each other. (Butler and Peltier) Plate tectonics shows how the upper part of the mantle and the crust are relatively brittle and cooler. They together constitute lithosphere. The lithosphere is fragmented into tectonic plates that carry the ocean and continents. Additionally, according to the theory the Indian continent is said to have travelled approximately 6,000 km northward before colliding with the Asian plate, an incident that took place over 57 million years ago. Also it is believed that the Tethys Ocean must have existed between Africa and Eurasia before the collision of the Indian and Eurasian plates. A chronology of motion that is based on palaeomagnetic analysis evidence the long and impressive journey of the Indian plate as fossils have been recovered from ocean drilling. According to analysis, a slow and sustained convergence led to formation of Himalayas that span Pakistan, India and Nepal among other countries. Similarly, the Eurasian plate suffered an uplift following the collation that led to rise of the great Tibetan plateau. Tectonic plates can be estimated from a variety of space geodetic technologies among the GPS, SLR and VLBI.
The modern day scientific theory of plate tectonics is based on continental drift theory but is transcending beyond contributing to research in earth science and other scientific fields. Plate tectonics is able to explain geological features of the earth as well as the long standing human concerns for public safety especially escalating from natural disasters and have immensely benefited from the understanding of the earth’s dynamics. Further, geologists and scientists have been able to identify volcano prone and earthquake vulnerable regions using plate tectonic model thereby contributing to reduction of casualties. The theory has contributed to the recognition that the earth’s natural resources are limited and vital to existence and development of human population. This has given rise of the need to explore untapped potential of natural resources that lie on the ocean floor. Additionally, finding and developing these resources constitute a challenging and important problem in the future research.
Plate tectonic studies expose earthquakes and volcanic eruptions as potential hazards to people who reside near active sites. It is said that earthquakes which occur beneath oceans or seas give rise to powerful tsunami waves which can travel thousands of miles causing colossal damage. For instance, the 2004 tsunami is recorded to be the largest and deadliest earthquake to have ever occurred. Plate tectonics also addresses the issue ofpredictability to mitigate the impacts of natural disasters. The tools of plate tectonics are essential to investigate properties of the plate boundary motion, surface strain, and the dynamics of the earth’s interior and mechanical properties of the earth’s crust. The theory is presently embraced in technology for modeling of these phenomena in which the technology is applied in establishing robust and reliable warning systems that are capable of predicting volcanic eruptions, tsunamis and earthquakes as well as minimizing material and human loses.
Plate tectonics is the basic organizing unit of earth sciences because it explains: why the continents move across the earth, first order land forms, volcanoes, fossil record, why oceans and continents are different, and earthquakes among others. Wegener’s continental drift theory provides the modern theory of plate tectonics that is widely used by the Geological Society of America. In fact, in 2006 it was proposed that earth is the only planet with tectonic plates.
Wegener intuition was ahead of the development of science for nearly half a century. Courage and the internal logic of the concept of continental drift first captured the minds of many of his contemporaries. That was one of weaknesses of Wegener's hypothesis was the difficulty of explaining the "mechanism" of why continents are drifting. In the thirties and forties, this explanation gave the Scottish geologist Arthur Holmes. He suggested that the force drifting the continents could be the flows of matter existing in the mantle and driven by the temperature difference. In this warm currents rise up and cold ones fall down. After a few years of calculations, which showed that the mechanism of a possible drift in the form in which it was presented Wegener was unreal. After years of hype around the Wegener's hypothesis popularity quickly waned. This was largely due to the tragic death of Alfred Wegener in 1930 in the ice of Greenland.
In fact, the ocean remained almost the same inaccessible to researchers, as before. New facts appeared just a bit, and interest in the theory of continental drift gradually waned. However, it managed to make geologists to explore the seas and oceans, and gave impetus to the development of remote sensing research. In particular, began to develop geophysical methods that can shine through the bottom of the deep, and receive continuous recording of the underwater topography of the coast to the abyss.
Great importance was the improvement of devices echolocation. Thanks to the widespread adoption of sonar in the Navy, and later on the research vessels in a short period of time there was a revolution in our knowledge of the topography of the seabed. This revealed an extremely complex geological structure of the ocean, which varies the peripheral and central parts of it. The era of intensive accumulation of evidence that led eventually to a revolutionary revision of the entire system of views on the history of both the ocean floor, and also the world has begun.
Moving basalt layer, he likened as the "endless transfer belt" that moves the continents. It took half a century right up to the end of the sixties of the twentieth century the idea of the large movements of the earth's crust turned out from a hypothesis into a detailed theory of plate tectonics.
In 1962, Alfred Wegener would be 82 years old, and he might live to see the triumph of his hypothesis. After his death almost 30 years appeared a few new facts, and the interest in it gradually faded away. However, this hypothesis still encourages beginning a serious study of geological composition of the rocks under the bottom of the seas and oceans.
The fate of the hypothesis of "continental drift" and clearly illustrates how difficult is the way of productive hypothesis to explain the undeniable factsaccumulated in the study of nature, to create a scientific theory, recognized by the international scientific community and the policy adopted by the practice. Scientists, authors of these hypotheses are the true benefactors of humanity. They usually have to overcome the conservatism of opinion to stand, the usual models in the science of his time. This is natural and useful in many ways. But very often on the way to the recognition of their discovery is yet another obstacle: the fierce opposition of their own less fortunate colleagues. And it is also understandable. Today Wegener's hypothesis is widely recognized and developed according to the level of modern science.
