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Chapter 1.2 Earth’s Spheres Earth • The only planet currently known to support life. • This capacity is due to the interactions among its 4 spheres… – Atmosphere – Hydrosphere – Geosphere – Biosphere Sphere #1 THE ATMOSPHERE What Is the Atmosphere? • A mixture of gases, mostly nitrogen (N) and oxygen (O) with smaller amounts of argon, carbon dioxide, and other gases • Held to the Earth by gravity • Thins with altitude Why Is the Atmosphere Important? • Supports Life – Animals need oxygen – Plants need carbon dioxide (CO2) • Regulates Climate – Retains heat at night – Shields from sun’s radiation during the day – Wind transports heat from Equator and cold from Poles Sphere #2 Geosphere The Geosphere • The solid Earth – Rocks, mountains, beaches, ocean basins, magma, mantle • The geosphere is slowly changing – Volcanic eruptions form new land – Mountains are uplifted – Continents are in slow but constant motion Sphere #3 THE HYDROSPHERE What Is the Hydrosphere? • All the earth’s water • Most of this water is salt water • 3% of the hydrosphere contains fresh water – Most of this water is frozen in glaciers – Remaining water is found in groundwater, lakes, water vapor, and river water. • All the water on Earth is recycled… – No new water is ever created! Sphere #4 THE BIOSPHERE What Is the Biosphere? • The zone inhabited by life – Includes the uppermost geosphere, the hydrosphere, and lower atmosphere • Includes all forms of life – Single-celled protozoans, to jellyfish to redwood trees to people.