Ii how does the density vary from the crust to the

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(ii) How does the density vary from the crust to the core? (iii) Briefly discuss the evidences to confirm that the earth crust is density in homogenous 3.4 Surface Structure of the Solid Earth The surface of the solid earth witnessed series of features such as oceans and continents which are consequences of geological events that took place over a long period of time; some of the features are explained below. 3.4.1 Formation of Continents, Ocean and Atmosphere (i) Continents: Lava flows as a result of volcanism from the interior to the outer layer cooled and became continent. (ii) Oceans: From the interior of the solid earth as a product of the Process of heating up and differentiation, some water bearing elements released their water molecules which accumulate on the surface to form the oceanic water. (iii) Atmosphere: Out-gassing , resulting from differentiation and some gas releasing chemical reactions brought about much gasses that accumulated above the solid earth. 3.4.2 Global distribution of continents and oceans
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- 38 - About 45% of the earth surface has sea-sea antipodal and 1.4% has land-land antipodal. Northern hemisphere has 60% land and 40% water, while southern hemisphere has 61% water and 39% land. In general, earth’s surface has 29% continent and 71% is covered by ocean. The total world area is approximately 2 6 10 510 km . 3.4.3 Significant Surface Features of Oceans . Elevation h is the height relative to see surface on the continent. Average elevation of continents is 0.88 km. Average depth or ocean floor is 3.8 km. Continental rocks are lighter than oceanic rocks. There is world wide mountain range that crosses the ocean basin 1000 km wide and 65,000 km long across the world. 3.5 Sequence of the Solid Earth’s Surface Ocean Surface (sea level) Continental self Continental slope Ocean water Ocean floor Mid -Ocean ridge h Elevation Continental platform Sea level Top surface h = elevation Geoids (sea level)
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- 39 - The earth’s surface is basically viewed in three forms: (i) The top surface is the continental platform wrinkled in nature. (ii) Geoids is the sea level, where sea water will flow to if the continent were to be tunnelled. In other word, geoid is the equipotential surface to which direction of gravity field is everywhere perpendicular. The vertical separation between the geoids and a point on the earth’s surface is the elevation. (iv) Ellipsoid is the ideal smooth surface of the earth in its oblate form. It sometimes coincides with geoids, but sometimes not. 3.6 Self-assessment Exercise 2 (1) What percentage of the earth’s surface is not covered by ocean water? (2) Define ellipsoid (3) What other name can you call a geoid? (4) How did the ocean form?
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- 40 - 4.0 Conclusion The interior of the earth compose of crust, mantle and core where the characteristics of each layer varies based on scientific evidences. Most of the surface structures of the earth are consequences of events that originated from the solid earth.
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