Heat in the Earth

Question 1

Conduction

Answer 1

transfer of heat through a material by atomic or molecular interaction within the material
- rocks are intermediate between Ionic and Covalent bonded

Question 2

Radiation

Answer 2

direct transfer of heat as electromagnetic radiation

Question 3

Convection

Answer 3

Transfer of heat by the movement of the molecules themselves
Advection is a special case of convection

Question 4

Conductive heat flow

Answer 4

Heat flows from hot things to cold things

Question 5

temperature gradient

Answer 5

proportional to the rate at which heat flows

• larger temp gradient = high heat flow
• small temp gradient = low heat flow

Question 6

ionic bonding

Answer 6

electrostatic bonds 
(Na_ and Cl- in salt NaCl)

Question 7

covalent bonding

Answer 7

sharing electrons

- diamonds, each carbon atom is surrounded by 4 other and each shares an electron)

Question 8

Earths system

Answer 8

• earth is an open system that exchanges energy and mass with its surroundings
• most heat from the sun is reflected back to the atmosphere
• heat from the sun arriving at the earth is 2x10^17 W (average over the surface this is 4x10^2 W/m2)

Question 9

Earths Heat

Answer 9

• earths interior is hot from volcanoes that expel hot magma and ash
• gets hotter the deeper you go underground

Question 10

Chile mine Heat Gradient

Answer 10

San Jose Mine, Chile 2010

• 700m
• 33oC
• higher than average geothermal gradient (average 30)

Question 11

Inner Earth system

Answer 11

• the earths system is all part of our planet and their interactions
• the heat from the interior is 4.7x10^13 W (8x10^-2 W/m2)
• heat from incoming solar radiation is 17300x10^13 W

Question 12

Heat flow mechanisms

Answer 12

• the outer electrons of metal atoms drift and are free to move
• when metal is heater the electrons gain kinetic energy and transfer it throughout the metal
• plastic and wood do not move like this and do not conduct heat as well

Question 13

Radiation as heat transfer

Answer 13

• when a substance is hot it glows
• heat can be transferred through radiation
• net transfer to heat from the hotter object t the cooler object
• works best through a transparent solid (sunshine through glass window)
• most minerals in the earth are dark in colour and opaque and therefore radiate heat slowly

Question 14

Convection as heat transfer

Answer 14

• refers to heat transferred by motion of material
• a kettle boiling, smoke rising etc. the heated fluid expands, rises (less dense) and then cools and sinks (process continues with further heating
• a continuous cycle is called a convection cell

Question 15

Oceanic heat flow

Answer 15

• heat flow is higher over young oceanic crust

- ocean crust forms by intrusion of basaltic magma from below

Question 16

Heat Transfer

Answer 16

• therefore, convection is the most efficient method of heat energy loss from the earth interior to the surface
• there is large scale motion beneath the earths surface

Question 17

Summary

Answer 17

• heat can be transmitted by; conduction, convection and radiation
• heat within the earth mostly originated from decay of radioactive elements
• young areas of crust have much higher heat flow than older areas