lecture 2

Question 1

earths formation

Answer 1

solar system coalesced from a rotating dust and gas cloud formed during a supernova

• accretion occured when particles accumulated into plantesimals. by attraction and then accumulated into proto-planets
• collisions generated intense heat

Question 2

proto-earth formation

Answer 2

as temperature rose from impacts, proto-earth melted and differentiated

• molten iron pulled to the core
• silica rocky material floated upward to form

Question 3

primordial

Answer 3

heat generated as the earth formed

- existing from the beginning of time

Question 4

meteorites

Answer 4

fragemnts of proto-planets and planetesimals that record earths accretion

Question 5

stony meteorites

Answer 5

made mostly from silica

• chondrites
• bumbly and have never been molten (before differentiation)
• oldest rocks in the solar system

Question 6

achondrites

Answer 6

type of stony meteorite that lacks chondrules

- orriginate from differentiated mantle

Question 7

stony-iron meteorites

Answer 7

silicates and nickel iron alloy

- boundary between outer silicate mantle and inner metalic core

Question 8

iron meteorites

Answer 8

made of nickel-iron alloy

- originated in the core of planetesimals

Question 9

4 types of meteorites

Answer 9

1. chondrites
2. achondrites
3. stony-iron
4. iron

Question 10

william thompson

Answer 10

estimated age of earth by CONDUCTION

• calculated 100 million years
• assumed earth was rigid, homogenous

Question 11

joohn perry

Answer 11

estimated age of earth by CONVECTION

- calculated 2-3 billion years

Question 12

henri becquerel

Answer 12

calculated age of earth including RADIOACTIVITY

• an additional internal source of heat
• age can be measured by decay of radioactive elemets

Question 13

naturally occuring radioctivity exposure

Answer 13

1. soil and rock
2. cosmic rays from space
3. food drink and air

Question 14

earths crust

Answer 14

outermost rocky layer
sedimentary rocks, granite and basalt
- average density of 5.5g/cm3

Question 15

xenolith

Answer 15

foreign rocks brought up from mantle

Question 16

earthquake seismic waves

Answer 16

reflected or refracted at major boundaries (core-mantle)

• p waves: faster and travel through liquid
• s waves: slower and cannot travel through liquid

Question 17

rheology

Answer 17

describes how materials deform under stress

Question 18

stress vs strain

Answer 18

stress = force/area
strain = deformation that occurs due to stress

Question 19

3 types of stress

Answer 19

1. compression- perpendicular to surface (shortening)
2. tension- perpendicular to surface (extension)
3. shear stress- parallel to surface (distortion)

Question 20

3 types of rheologies of solids

Answer 20

1. elastic- deformation is recoverable
2. brittle- may break at elastic limit
3. plastic- deformation is permanent

Question 21

ductile deformation

Answer 21

stress over long periods of time, plastic materials can flow
ex. brie cheese

Question 22

factors of rheology

Answer 22

time, temperature and pressure

Question 23

earths outer shell

Answer 23

liphosphere- solid, elastic
asthenosphere- soft plastic upper mantle
mesosphere- stiff plastic layer

Question 24

oceanic vs continental crust

Answer 24

oceanic- basalt (higher density)

continental- granite

Question 25

istostasy

Answer 25

equilibrium where lithosphere floats on denser, plastic asthenosphere

Question 26

isostatic adjustment

Answer 26

addition or subtraction of mass from flaoting object leads to change in elevation

Question 27

postglacial rebound

Answer 27

major glaciations at high latitudes

- surface is uplifted

Question 28

what drives mantle convection

Answer 28

• heat from the core
• heated from below by primordial heat and from within by radioactivity
• internal heat energy is responsible for earthquakes, tsunamis, volcanoes and rise of mountains (landsliding)

Question 29

sources of energy for natural hazards

Answer 29

• sun is nuclear fusion reactor: combining hydrogen to produce helium and releasing energy as heat and light
• uneven heating of oceans and atmosphere drives ocean currents