The Earth

Question 1

What is the albedo (fraction of light reflected) of Earth?

Answer 1

37%

Question 2

What is the diameter of earth?

Answer 2

12,700 km

Question 3

what is the mass of earth?

Answer 3

5.97 x 10 ^24 kg

Question 4

how old is the Earth?

Answer 4

4.5 billion years old

Question 5

what percent of elements make up thin layer of gas surrounding the earth#?

Answer 5

nitrogen: 78%
oxygen: 21%
argon: 1%
little water vapour
traces of carbon dioxide
ozone O3

Question 6

what kind of radiation is produced in the form of heat when the sun heats the atmosphere and where it is absorbed?

what does this drive?

Answer 6

infrared radiation , most absorbed by ground

large scale oceanic motions and global wind patterns

Question 7

why is there seasons on earth?

Answer 7

spring: earth 3% closer to sun in jan (23.5 degree tilt)
Sun is higher in sky summer (june/july northern hemisphere but december/jan southern) than winter. means more energy is on ground/sea better heating effect.

Question 8

what is escape velocity?

Answer 8

to get something to escape from earth, need to throw it with speed v =√2gR = 11.2 km/s

Question 9

what is the average speed of molecules in the atmosphere?

Answer 9

√3kBT /µ, where kB is Boltzmann’s constant,
T is temperature in “Kelvins”
and µ is the molecular mass (in kg)

Question 10

how do molecules leak away regarding escape velocity?

Answer 10

average speed comes within about factor of 6 of escape speed

Question 11

how can we probe the interior of the Earth?

Answer 11

seismic waves, created by earthquakes

Question 12

what are the two main types of seismic waves?

Answer 12

P waves: compressional waves, travel through solids and liquids. First to arrive at a site away form earthquake epicentre.

S waves: traverse/shear waves, cannot travel through liquid.

Question 13

what is the general structure of the earth?

Answer 13

crust, mantle, core

Question 14

how thick is the crust and what is the density?

Answer 14

60km thick, density less than 3g/cm^3

Question 15

describe the mantle? density?

Answer 15

solid, transmits S waves, not totally rigid, can be deformed over long period of time. 3.5 g/cm^3

Question 16

describe the outer core? density?

Answer 16

liquid, no s waves only p. contains iron with nickel and cobalt. 13 g/cm^3

Question 17

what is the overall average density of the core?

Answer 17

5.5 g/cm^3

Question 18

what is the dense core?

Answer 18

result of differentiation, when planet was molten heavy/dense material sank towards centre of planet due to gravity

Question 19

why was the Earth molten?

Answer 19

radioactive heating in interior, also impact of smaller bodies that merged to form earth, releasing heat

Question 20

Where are Earthquakes and volcanoes common?

Answer 20

boundaries of plates

Question 21

how do earthquakes happen?

Answer 21

adjacent plates slip along fault lines

Question 22

how do volcanoes form?

Answer 22

when mantle material can reach surface

Question 23

what renews the surface of the earth? how old is the surface of earth?

Answer 23

tectonic activity- milllions/100s of millions yrs

Question 24

what is the alignment of the magnetic field of earth?

Answer 24

aligned with rotation axis (11.5 degree tilt)

Question 25

what is the magnetosphere?

what does it prevent?

Answer 25

region enclosed by field lines

prevents charged particles from sun and elsewhere reaching earths surface

Question 26

why is the magnetosphere lopsided?

Answer 26

flow of charged particles from sun

Question 27

what are the northern lights?

Answer 27

solar flares disrupt magnetosphere allowing some particles to flow along magnetic field lines to poles; exciting molecules in upper atmosphere.

Question 28

what is a magnetic dynamo?

Answer 28

magnetic field produced when electrical charges move.