2 1) Why are some of Earth’s layers solid and others liquid 1) Why are some of Earth’s layers solid and others liquid? 2) Why doesn’t the Earth melt? 3) Why do Earth’s layers change?
3 The magic answer: HEAT TRANSFER! What is a good definition for Heat Transfer?
4 Heat Transfer:Remember this rule: Heat always moves from a warmer substance to a cooler substance(ex. holding an ice cube will make your hand begin to feel cold in a few seconds.)What are the 3 types of Heat Transfer?
10 2) Conduction: Heat transfer between materials that are touching What are examples of Conduction?
11 What are examples of Conduction? Example: When you walk barefoot on hot concreteExample: When a hot pot of water heats up a metal spoon.Example: A cold cast iron skillet is placed onto a stovetop. When the stove is turned on, the skillet becomes very hot due to the conduction of heat from the burner to the skillet.
12 What are examples of Conduction? A cube of ice is placed into your hand. Over time, heat conducted from the your hand to the ice cube will cause the ice to melt.When an athlete warms sore muscles with a heating pad
13 What are examples of Conduction? When a piece of hot lasagna is placed onto a porcelain plate, the plate will feel warm to the touch after several minutes due to the conduction of heat from the just-cooked food to the plate on which it sits.A shirt is placed on an ironing board to be ironed. Heat from the iron is conducted to the shirt, making it easy to iron out all those unsightly wrinkles and make the shirt look sharp.
15 3) Convection Movement of currents within a fluid When a liquid or gas is heated, the particles expand, or become less dense and riseWhen particles cool, they become more dense, and sink back to the bottomThis creates continuous convection cycles
16 What are the three important things to remember that cause convection cycles to happen?
17 Convection is caused by: Heating and cooling of the fluidChanges in the fluid’s densityThe force of gravity
18 During the convection cycle, as the warm particles expand and rise to the top, is the density of these particles increasing or decreasing?
19 Density is decreasing because as the particles get warmer, they expand (take up more room) and therefore become less dense.
20 As particles cool down, is the force of gravity stronger or weaker?
21 As particles cool down, their density is increasing, so the force of gravity is stronger.
22 Remember that objects that are more dense have a higher gravitational pull .
28 The same thing is happening in the Earth’s mantle
29 Earth’s MantleAs the core heats the lower mantle (which is solid), it becomes less dense so rises through the Asthenosphere to the LithosphereThe Lithosphere is cooling and becoming more dense, so it sinks into the AsthenosphereThis is a continuous process –Convection CycleThese convection cycles happen over millions of years