Most of the thermal energy at Earth’s surface comes from the Sun. Half of the solar radiation that reaches Earth is absorbed at the surface and converted to thermal energy. The atmosphere and lithosphere absorb thermal energy from the Sun. The lithosphere is the solid outer layer of Earth. The atmosphere is the layer of gases enveloping Earth. Earth’s Heat Sources 14.3 VOCABULARY lithosphere atmosphere troposphere hydrosphere albedo

The albedo of a surface is the degree to which it reflects light. Earth’s interior has large quantities of thermal energy as a result of the planet’s formation and continuing radioactive decay. Earth’s hot core is well insulated because thermal energy cannot easily move through Earth’s lithosphere by conduction, convection, or radiation. Earth’s Heat Sources 14.3 VOCABULARY lithosphere atmosphere troposphere hydrosphere albedo ALBEDO CLIP:

Heat and Thermal Energy Sources Thermal energy influences temperature, density, pressure, and a substance’s physical state. Temperature is an indicator of the average kinetic energy of particles, while thermal energy includes both kinetic energy and potential energy from the motion of particles and their relative positions and forces of attraction. 14 CHAPTER

Heat and Thermal Energy Sources Heat is defined as the transfer of thermal energy from one object to another because of differences in their temperature. Thermal energy can be transferred by conduction, convection, and radiation. 14 CHAPTER

Heat and Thermal Energy Sources Most of the thermal energy at Earth’s surface comes from the Sun. Earth’s interior has large quantities of thermal energy. The core is well insulated by land masses and is extremely hot as a result of the planet’s formation and continuing radioactive decay. 14 CHAPTER

Transfer of Energy on Earth Activity Take a look at Figure 3 on page 437. Discuss with your neighbour why we have different seasons Can you predict what causes the seasons? What would have to occur for Earth to experience no seasons? Read “Reasons for the Seasons” on page 437 for more information. 15 CHAPTER

Transfer of Energy on Earth 15 Key Ideas Atmospheric pressure results from gravity and the force of the atmosphere pushing down on itself. Uneven heating of air produces differences in density and air pressure. Wind results when air in high-pressure regions moves toward regions with lower air pressure. Latitude and landscape influence the absorption of incoming solar radiation. Global prevailing wind patterns influence ocean currents and the formation of weather systems. CHAPTER

The force of gravity causes the atmosphere to exert significant pressure at Earth’s surface. This is called atmospheric (or air) pressure. Atmospheric pressure decreases with altitude. Atmospheric Pressure and Influences 15.1 VOCABULARY atmospheric pressure kilopascal low-pressure cell high-pressure cell isobars

Air expands as it is heated, resulting in less dense, warm air with lower atmospheric pressure. The warmer, less dense air floats up through surrounding cooler, denser air which flows in underneath the rising air. Low-pressure cells contain warm, rising air with clouds and precipitation. High-pressure cells contain cool, falling air with little moisture. Atmospheric Pressure and Influences 15.1 VOCABULARY atmospheric pressure kilopascal low-pressure cell high-pressure cell isobars HIGH/LOW PRESSURE CLIP: