4.) PLATE TECTONICS 10 Mt. Everest 8850 meters Land 29.296 Avg. elevation of and
ID: 299483 • Letter: 4
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4.) PLATE TECTONICS 10 Mt. Everest 8850 meters Land 29.296 Avg. elevation of and 840 meters level Avg. depth of oceans 3729 meters margin Deep ocearn Trenches Ocean-70.8% 10 Mariana Trench 11,022 meters 24 20 16 8 0 Millions of square killometers Percent of Earth's Surface 100 150 200 250 300 350 400 450 500 20 40 60 80 100 Percentage of area Percentages of the Earth's surface at different elevations are plotted above. This is called the Hypsographic Curve a.) Why are there two elevations that cover so much of the surface of the earth (why is there a bimodal distribution of elevations)? (4 points) b.) Why is there so much of the earth's surface at or near sea-level? (3 points) c.) Why haven't the tallest mountains (e.g. the Himalayas) eroded down to sea-level? Why haven't the deepest ocean trenches (e.g. the Mariana Trench) filled up with sediment? (3 points)Explanation / Answer
Answer -
1.There is bimodel distribution of elevations due to two variations in crustal composition.there are two types of crust - continental crust and oceanic crust. Continental crust composition is written as sial (Composed primarily of oxides silicon and aluminium) and oceanic crust composition is known as sima(oxides of silicon and magnesium).
2. According to hypsometric curve, only 29% of earth's surface is above sea level other 71% has elevation below sea level.there are many reasons but one is erosion of continental features that reduces their elevation. The eroded materials than find their way to the oceans bottom because of gravity which ultimately reduces the oceanic and continental elevations.for example older mountains have less elevation than younger ones. So most of the earth surface features are close to sea level.
C. Due to plate tectonics there is an uneven distribution of landmass on earth.tallest mountains which are young like Himalayas will take more time to erode and to reach down to sea level including various factors of weathering and erosion. Similarly,the accommodation levels of oceans through various process of transgression, aggradation,retrogression which are the result of tectonics, eustasy and climate will determine when and whether the oceans can be filled up With sediments.
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