Define: universe. Explain what the solar system is. Analyse how the Earth is influenced by its position in the solar system. Would life be possible on Earth if all the water was solid? Explain your answer. List and define the layers of the Earth. K E Y Q U E S T I O N S A planet with layers The Earth is made up of several layers: The atmosphere is the layer of gases that surrounds the planet. The hydrosphere is made up of the water on Earth . It includes the oceans, seas, rivers, glaciers, polar ice caps, etc. The geosphere is the solid part of the Earth . (4) The biosphere is the area in which life exists. (3) The Earth's internal structure The geosphere has concentric layers. From the surface to the centre of our planet there are several layers. (4) (A) The highest altitude at which birds can fly. (B) The highest point for life in the tropics. (C ) The highest point for life in the temperate zone. (D) The maximum concentration of living things. (E ) The lowest point at which living things can exist. The crust is the external and thinnest layer of the geosphere. It is made of rock. The continental crust is thicker and more rigid than the oceanic crust and is composed mainly of granite. The oceanic crust is composed almost exclusively of basalt. The mantle is beneath the crust. Its temperature is higher than that of the crust. The upper mantle contains less dense materials than the lower mantle. The core is the deepest layer and extends to the centre of the Earth. It is made of iron and nickel. The outer core is in a liquid state. The inner core is solid. 10,000 m 8,000 m 6,000 m 4,000 m -4,000 m -6,000 m -8,000 m -10,000 m 2,000 m -2,000 m 0 m A B C D E 3. The biosphere 60-70 km 2,900 km 6,378 km upper mantle lower mantle outer core inner core oceanic crust continental crust 4. The geosphere 11 1
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