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Chapter 12: Earth Science. A theory proposed by Alfred Wegener in the early 20 th Century. The drifting of continents on plates like rafts. Continents slowly change in shape and size as they move in different directions at the rate of fingernail growth on the mantle.
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A theory proposed by Alfred Wegener in the early 20th Century. The drifting of continents on plates like rafts. Continents slowly change in shape and size as they move in different directions at the rate of fingernail growth on the mantle. The theory was rejected at the time, because Wegener could not explain how it occurred. What is Continental drift?
2.Wegener’s Theory of Continental Drift Alfred Wegener 1880-1930
In the 20th century ,when German scientist Alfred Wegener proposed the continental drift theory, the idea was revolutionary . The apparent match on a world map between South America’s eastern coastline and Africa’s western gave Wegener his first piece of evidence for continental drift .To Wegener and many others, the fit appeared too close to be coincidental. Wegener suggested that, millions of years ago, all the continents were joined as a “super continent.” He named the giant land mass pangaea, from the Greek words pan, meaning all, and gaea, meaning earth. In truth, the continental edges do not match as perfectly as pieces of a puzzle. A better alignment is obtained by matching the continental shelves, which are the submerged original shorelines of continents. Wegener also compared geological structures, fossils and evidence of ancient glaciers on different continents. These clues did not seem significant until Wegener placed the continents together. It takes millions of years for continents to cover such a distance. It took approximately 300 million years for the world to form this way. Wegener’s first clue that the continents were in motion came from his and others observations of world maps
3. Describe 4 fossils that provide evidence to support continental drift.
Evidence for continental drift is all across the board. Similar plant and animal fossils are found around different continent shores, mountains, and valleys suggesting that they were once joined. The fossils of 1.)Mesosaurus, a freshwater reptile rather like a small crocodile, found both in Brazil and South Africa, is one example. Another example is; fossils of the land reptile 2.)Lystrosaurus from rocks of the same age from locations in South America, Africa, and Antarctica. 3.) Glossopteris Greek, meaning tongue, because the leaves were tongue-shaped is the largest and best-known genus of the extinct order of seed ferns known as Glossopteridales More than 70 fossil species of this genus have been recognized in India alone, with additional species from South America, Australia, Africa, Madagascar and Antarctica. Lastly 4.)Cynognathus was a meter-long predator of the Early to Middle Triassic. Found in S.A, A, and in shores of India I believe that the continents were once joined together. (Pangaea) Because how can so many different mammals of the same species have traveled roughly over 6000 km of open ocean. Additionally Glossopteris- a fern like plant have traveled through the vast ocean. It is an extinct plant and would have not grown there naturally for it cannot survive the cold southern hemisphere of were Antarctica lays now, thus continental drift must have been true and still is.
4. How does the location of coal deposits support the theory of continental drift?
Coal forms from the decomposition of living things. The life forms that died and decayed into coal deposits lived in tropical climates. However, coal deposits have been found in places like Siberia and Northern Canada. They do not have tropical climates, which suggests they must have been in a warmer location then they are now.
5. How does Paleoglaciation support the theory of continental drift?
Magnetic reversal is the process in which Earth’s magnetic fields completely reverse direction over thousands of years. Earth’s magnetic south pole becomes its magnetic north pole, and vice versa. It is believed that this happens when the motion of liquid iron in the earth core changes. Magnetic Striping is the pattern of stripes that is formed by iron containing minerals on the sea floor. The alternating stripes switch every time the is a magnetic reversal.
10. How does magnetic striping support the theory of continental drift?
Magnetic striping helps us to explain sea floor spreading. During sea floor spreading, new magma rises and pushes aside older rocks so that is can replace it. Magnetic striping shows us that the rock does indeed get older as you go farther from the spreading ridge where sea floor spreading takes place. By supporting sea floor spreading, magnetic striping supports the continental drift theory. The continental drift theory would not be possible without sea floor spreading.
The Crust • The crust is the outermost layer of the Earth. • It is composed of solid, brittle rock. • “Continental crust” is made of granite and can be as thick as 70 km. • “Oceanic crust” is made from a more dense rock called “balsalt,” and can be as thick as 10 km.
The Upper Mantle • The upper mantle is the outermost layer of the mantle, and lies just below the crust. • It’s made of partly molten rock, mostly iron and magnesium. It has the consistency of thick toothpaste. • It is approximately 660 km thick.
The Lower Mantle • The inner layer of the mantle is made up of solid, dense material, mostly magnesium and iron, like the upper mantle. • The lower mantle is about 2225 km thick, making it the second thickest layer in the Earth.
The Outer Core • The outer core is the only layer in the Earth to be completely liquid, which is due to the intense heat at the centre of the Earth. • It is also the thickest layer in the Earth, being 2300 km thick. • It is composed of a mixture of mainly iron and nickel.
The Inner Core • The inner core lies at the very centre of the Earth. • It is a sphere with a radius of 1200 km. • Even though you would think, because of the intense heat (5000°C to 6000°C), that this layer would be liquid, due to incredible pressure, it is solid. • It is almost entirely made of iron, with some nickel.
12. Find and describe the tectonic mapping symbols that show the movement of the tectonic plates.
Divergent plate boundaries mark the areas where tectonic plates are separating apart.-Divergent boundaries within continents initially produce rifts which produce rift valleys.-Most Divergent plate boundaries occur between oceanic plates and exist as mid- ocean ridges. How are Divergent Boundaries Formed? Two plates move apart from each other and the space that is created is filled with new crustal material sourced from molten magma that forms below. 13. What is a divergent plate boundary? These boundaries are thought to be somewhat associated with hotspots.
Convergent plate boundaries are where the tectonic plates collide. There are three different types of convergent plate boundaries. 14. What are Convergent Plate Boundaries?
a.Oceanic-Continental Plate Convergences • Where an oceanic and a continental plate collide. The dense oceanic plate slides beneath causing deep under water trenches. Small mountains form on the surface, and if conditions are right magma may make its way to the surface.
b. Oceanic-Oceanic Plate Convergence • The collision of two oceanic plates. The heavier and denser plate will always slide beneath due to cooling. The collision will produce long chains of volcanic islands, also known as a volcanic island arc.
c.Continental-Continental Plate Convergence • Where two continental plates collide. One of the plates will not slide under; instead both side of the plate with crumple and fold. The produce of this are great mountain ranges. Himalayas are continues to raise several cm per year due to, continues movement of one of the plates.
http://www.youtube.com/watch?NR=1&feature=endscreen&v=tIuk2blBzHshttp://www.youtube.com/watch?NR=1&feature=endscreen&v=tIuk2blBzHs
18. What is an Ocean Ridge? • An Ocean Ridge is a Mountain Range that is formed underwater caused by Plate Tectonics • This is also commonly know as Oceanic spreading center which is the reason for seafloor spreading • The Sea floor being uplifted like this is caused by hot air know as convection it brings up magma which forms into underwater mountain ranges
These mountainous ranges are the largest on the planet spanning a total distance of 80,000 Km • These mountain ranges are found in every ocean across the world which is all interconnected • Oceanic Ridges are like a boarder between two Plate Tectonics
• Epicentre: the point on the surface of the earth directly above the focus, the source from which the earthquake or underground explosion originates. • It is determined by measuring wave intensity on seismographs. • Knowing where the epicentre is can show where the focus is, thereby showing where the tectonic plate boundaries are. (If it is a tectonic earthquake.
http://www.glogster.com/islebbach/seismic-waves/g-6lsd8838ipfqjkpqp2k97a0http://www.glogster.com/islebbach/seismic-waves/g-6lsd8838ipfqjkpqp2k97a0 21. Identify and describe the 3 earthquake waves.
