Timeline of Plate Tectonic Theory
1) What was believed BEFORE continental drift.
-Find one theory from Pre-1910 that describes how humans explained such phenomena as earthquake, volcanoes, mountains, etc.
The Conflagration Theory : According to this theory, supported by the Vulcanists of the 1700s, the mountains and all land formations were formed by sudden shocks which came from the inside movement of the earth such as earthquakes and volcanoes. This theory was based on the thought that some geologic events happened over long periods of time by the hand of God and others quickly by the force of nature.
2) The theory of Continental Drift
- Who came up with it?
- When did they come up with it?
- What did it state? What was the evidence?
- Was the theory accepted? Why or why not ?
The continental drift theory states that the relative positions of the continents on the Earth’s surface have changed considerably through geologic time. Although Abraham Ortelius first proposed this theory in 1956, Alfred Wegener put the first detailed theory of the continental drift forth in 1912. He believed that all of the continents were united into a vast supercontinent, which he called the Pangaea. Later, Pangaea broke into two supercontinental masses (north and south). The present continents began to split apart, drifting into their present positions. Wegener searched for evidence to further develop his theory and came across a paleontological paper suggesting that a land bridge had once connected Africa and Brazil. This was the attempt to explain the paleontological observation that the same fossilized plants and animals from the same period were found in South America and Africa. Another observation favoring the theory was the presence of evidence for continental glaciation in the Pennsylvanian period. The theory of the continental drift was not generally accepted until the 1950s and 60s, when a group of British geophysicists reported on magnetic studied of rocks from many places and from each major division of geologic time. They found that for each continent, the magnetic pole had changed position, forming a smooth curve or pole path.
3) The Theory of Plate Tectonics
- Who came up with it?
-Alfred Wegener came up with the theory of continental drift in 1912 which led to the debate which resulted 50 years later in the theory of plate tectonics
-Fred Vine, Drummond Matthews 1963
-Henry Hess's theory of "seafloor spreading" offered a compelling driving mechanism for Wegener's continental drift, but it needed more proof
- When did they come up with it?
1960s
- What evidence did they use to support their theory?
Evidence that led to the development of plate tectonic theory in the 1960s came primarily from new data from the sea floor, including topography and the magnetism of rocks.
In 1963, Fred Vine and Drummond Matthews, two British geologists, joined the topographic map of the Mid-Atlantic Ridge with the symmetric bands of magnetism on the seafloor . Where the navy ships mapped strong magnetism, rocks showed normal polarity; where they mapped bands of weak magnetism, the rocks showed reversed polarity. The bands not only paralleled the mid-ocean ridges, but were patterned symmetrically about the crest of those ridges
Be sure to include how plates move.
From seismic and other geophysical evidence and laboratory experiments, scientists generally agree with Harry Hess' theory that the plate-driving force is the slow movement of hot, softened mantle that lies below the rigid plates beneath the lithosphere
4) The theory of Hot Spots
- Who came up with the theory?
In 1963, J. Tuzo Wilson, the Canadian geophysicist who discovered transform faults, came up with an ingenious idea that became known as the "hotspot" theory. Wilson noted that in certain locations around the world, such as Hawaii, volcanism has been active for very long periods of time
- When?
1963
- What evidence did they use to support their theory?
Wilson hypothesized that the distinctive linear shape of the Hawaiian Island-Emperor Seamounts chain resulted from the Pacific Plate moving over a deep, stationary hotspot in the mantle, located beneath the present-day position of the Island of Hawaii. Heat from this hotspot produced a persistent source of magma by partly melting the overriding Pacific Plate. The magma, which is lighter than the surrounding solid rock, then rises through the mantle and crust to erupt onto the seafloor, forming an active seamount. Over time, countless eruptions cause the seamount to grow until it finally emerges above sea level to form an island volcano. Wilson suggested that continuing plate movement eventually carries the island beyond the hotspot, cutting it off from the magma source, and volcanism ceases. As one island volcano becomes extinct, another develops over the hotspot, and the cycle is repeated. This process of volcano growth and death, over many millions of years, has left a long trail of volcanic islands and seamounts across the Pacific Ocean floor.
- Is the theory accepted?
Yes, the theory was accepted.
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