Chapter 1 Section 2 Convection Currents and the

Chapter 1 Section 2: Convection Currents and the Mantle

Remember from Section 1: • The Earth’s molten outer core is nearly as hot as the surface of the sun. • This heat affects the mantle through heat transfer: The movement of energy from a warmer object to a cooler object.

Remember from Section 1: • Heat is always transferred from a warmer substance to a cooler. Example: holding an ice cube. • 3 types of heat transfer: radiation, conduction and convection.

Radiation, pg. 25 • Radiation is the transfer of energy through empty space. • Sunlight is radiation that warms Earth’s surface. • It takes place with no direct contact between a heat source and an object. • Other examples: Heat from a light bulb, heat from an open fire.

Conduction, pg. 26 • Conduction: The heat transfer by direct contact of particles of matter • Examples: Pot of water on the stove, thermometer.

Convection, pg. 26 • Convection is heat transfer by the movement of a heated fluid (liquid or gas) • Heated particles of fluid begin to flow, transferring heat energy from one part of the fluid to another. • Convection occurs between differences in temperature and density within a fluid. • Remember: Density is the amount of mass in a volume of a substance.

How Does Convection Work? • As a liquid/gas heats up, particles move faster and spread apart and occupy more space. Density decreases • As a fluid cools, particles move slower and settle closer together and density increases.

How Does Convection Work? • Warm/less dense fluid moves upward and floats over the cooler, denser fluid. **Think of the air– where do we find warm/cold air? ** • As it spreads out and cools it becomes denser and gravity pulls it back down where it is heated again.

How Does Convection Work? • There is a constant flow where the cooler liquid/gas continuously sinks to the bottom as the warmer fluids rise.

Convection • A convection current is the flow that transfers heat within a fluid. • This continues as long as heat is added. • Without heat, convection currents will stop as all material reaches the same temperature.

Convection in Earth’s Mantle, Pg. 27 • Earth’s mantle responds to heat. The heat source is the Earth’s core and the mantle itself. • Hot columns of mantle material rise slowly through the asthenosphere.

Convection in Earth’s Mantle, Pg. 27 • At the top of the asthenosphere, the hot material spreads out and pushes cooler material back towards the lower asthenosphere. • This cycle of rising and sinking has occurred inside the Earth for more than 4 Billion years!

Journal • Describe what it’s like to be water that is being boiled. – Where are you moving fast or slow – Are your particles close together or further apart (where does that happen) – How much space are you taking up. – When are you less dense or more dense and what happens? (Sink or rise) – Relate this idea to how convection is occurring in the mantle (asthenoshere)