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Similarity of shoreline shape noticed
Sir Francis Bacon noted the similarity of the shapes of the shoreline of eastern South America and western Africa. However, he did not propose that the continents were once joined...... -
Geological Change
Charles Lyell offers proof that the Earth evolved slowly in his multivolume 'Principles of Geology: An Attempt to Explain the Former Changes of the Earth's Surface by Reference to Causes Now in Operation', published between 1830 and 1833. He advocates the then-controversial idea of uniformitarianism (idea that the Earth was shaped entirely by slow-moving forces acting over a very long period of time). Catastrophism, geologic idea using biblical chronology to date Earth was more accepted. -
First suggestion that continents were once linked together
Antonio Pellegrini suggested that the continents were all linked together during the Carboniferous and later split apart. This suggestion was based on the similarities he discovered between plant fossils found in North America and Europe -
Proposal that continents were once linked, via land bridges, to form Gondwana
Edward Suess noted similarities between PPaleozoic plant fossils in India, Australia, Africa, South America and Antarctica and evidence for glaciation on these landmasses, He proposed these landmasses were all once joined together in a supercontinent (Gondwana) by land bridges which later sank beneath the ocean -
Suggestion of the existance of the Earth's Core
Richard Oldham, a seismologist, determines that earthquake waves move through the central part of the Earth much slower than through the surrounding mantle; from this he implies that the Earth has a core composed of liquid. -
Magnetic Field Reversal
Bernard Brunhes discovers that the Earth's magnetic field has changed direction and reversed itself, His paleomagnetic study of the clay baked by a Miocene lava flow 13 million years ago provides the evidence. it is nearly 50 years though before his theory is accepted by the scientific community. -
Radiometric Dating
Bertam Boltwood discovers how to calculate the age of rock by measuring the rate of its radioactive decay. His observations and calculations put Earth's age at 2.2 billion years. Although we now think Earth is nearly twice that age, this number was a dramatic increase over the accpeted age at that time. Boltwood's formulas are compatible with several radioactive elements including C-14, which has been used to date historical artifacts. -
First suggestion of existance of Pangaea - Continental Drift
Alfred Wegener proposed that the continents were once joined in one supercontinent (Pangaea), which began breaking up 200 million years ago. Produced maps showing movement of continents to their current locations via a process he called 'Continental Drift'. Wegener's evidence consisted of the 'fit' of South America with Africa, fossil distribution and geological similarities. -
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No support for Wegener's theory of Continental Drift
People contested Wegener's theory as no one could think of a mechanism which would be stro.ng enough to drive the continents across the oceans -
Earth's Inner Core discovered
Inge Lehmann records some seismic waves from deep inside the Earth's core do not pass through, but instead are reflected back. Therefore, from this, it becomes clear that the Earth has an inner cpre consisting of a small, solid iron sphere that is surrounded by a thick outer layer Core composed of a liquid iron. -
Mid-Atlantic Ridge discovered
Mid-Atlantic Ridge discovered during World War II thanks to the increased use of SONAR equipment. There were also investigations into the magnetic properties of the rocks in the sea floor. -
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Sea floor spreading
Adding his own data on changes in sea floor depth and geology to discoveries of his peers, Harry Hess proposes that Wegener's theory of continental drift is a result of sea floor spreading. He hypothesises that molten magma from beneath the Earth's crust is oozing up between the plates in the Great Global Rift (now referred to as the Mid-Ocean Ridge). As the hot magma cools, it expands and pushes the plates out from the rift, causing the Atlantic to get wider over time. -
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Plate Tectonics theory formulated
The work of many scientists reveals that the Earth's surface is broken into several interconnected plates of rock. Earth;s outermost layer, the lithosphere, is broken into at least 7 large, rigid pieces. These plates are moving in different directions and at different speeds (normally about 1 to 4 inches per year) and colliding, pulling apart and sliding past each other. All the action at the plate margins produces phenomena such as mountains, volcanoes and earthquakes. -
Linear volcanic chain proposal
Robert Dietz, Bruce Heezen and Harry Hess proposed that linear volcanic chains in ocean basins are sites where the new sea floor is erupted and then this moves towards the sides of the oceans and is replaced in the middle by younger material. -
Hypothesis presented explaining magnetic reversal stripes on ocean floor
Fred Vine and Drummond Matthews proposed a hypothesis that explained the magnetic reversal stripes on the ocean floor. They said that the new oceanic crust formed by the solidification of basalt magma acquired its magnetism in the same direction as the prevailing global magnetic field. -
Reinterpretation of Wegener's theory
J Tuzo Wilson reinterprets Wegener's theory and is the first to use plates to describe different sections of the Earth's surface. He also proposes the Wilson Cycle. -
Earthquake Zones
Bryan Isacks, Jack Oliver, and Lynn Skyes recognize that slabs of material rigid enough to sustain earthquakes are descending into deep trenches, creating earthquake zones. -
Sea floor hot springs
The first seafloor hot springs are discovered at the Galápagos Rift in an expedition led by Jack Corliss, of Oregon State University and Robert Ballard of Woods Hole Oceanographic Institution. The scientists observe unique and unexpected animal communities living in the seafloor vents.
