The Earth Flashcards
What is the albedo (fraction of light reflected) of Earth?
37%
What is the diameter of earth?
12,700 km
what is the mass of earth?
5.97 x 10 ^24 kg
how old is the Earth?
4.5 billion years old
what percent of elements make up thin layer of gas surrounding the earth#?
nitrogen: 78%
oxygen: 21%
argon: 1%
little water vapour
traces of carbon dioxide
ozone O3
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?
infrared radiation , most absorbed by ground
large scale oceanic motions and global wind patterns
why is there seasons on earth?
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.
what is escape velocity?
to get something to escape from earth, need to throw it with speed v =√2gR = 11.2 km/s
what is the average speed of molecules in the atmosphere?
√3kBT /µ, where kB is Boltzmann’s constant,
T is temperature in “Kelvins”
and µ is the molecular mass (in kg)
how do molecules leak away regarding escape velocity?
average speed comes within about factor of 6 of escape speed
how can we probe the interior of the Earth?
seismic waves, created by earthquakes
what are the two main types of seismic waves?
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.
what is the general structure of the earth?
crust, mantle, core
how thick is the crust and what is the density?
60km thick, density less than 3g/cm^3
describe the mantle? density?
solid, transmits S waves, not totally rigid, can be deformed over long period of time. 3.5 g/cm^3
describe the outer core? density?
liquid, no s waves only p. contains iron with nickel and cobalt. 13 g/cm^3
what is the overall average density of the core?
5.5 g/cm^3
what is the dense core?
result of differentiation, when planet was molten heavy/dense material sank towards centre of planet due to gravity
why was the Earth molten?
radioactive heating in interior, also impact of smaller bodies that merged to form earth, releasing heat
Where are Earthquakes and volcanoes common?
boundaries of plates
how do earthquakes happen?
adjacent plates slip along fault lines
how do volcanoes form?
when mantle material can reach surface
what renews the surface of the earth? how old is the surface of earth?
tectonic activity- milllions/100s of millions yrs
what is the alignment of the magnetic field of earth?
aligned with rotation axis (11.5 degree tilt)
what is the magnetosphere?
what does it prevent?
region enclosed by field lines
prevents charged particles from sun and elsewhere reaching earths surface
why is the magnetosphere lopsided?
flow of charged particles from sun
what are the northern lights?
solar flares disrupt magnetosphere allowing some particles to flow along magnetic field lines to poles; exciting molecules in upper atmosphere.
what is a magnetic dynamo?
magnetic field produced when electrical charges move.
