1- planet earth Flashcards
what is the earth’s mean diameter?
13 000 km
what is the largest terrestrial planet?
earth
what shape is earth?
oblate spheroid
how is the earth an oblate spheroid?
The polar diameter is smaller than the equatorial diameter by 42km
How much of the earth is covered by water?
~70% (71%)
what are the earths four major internal divisions?
crust, mantle, outer core, inner core
what is the thickness of the earth’s crust?
the earth’s crust ranges in thickness from 0-70km thick
what is the continental crust made up of?
low-density rocks such as granite.
what is the thickness of the oceanic crust?
up to 10km thick
what is the oceanic crust made up of?
denser rocks such as basalt
what does the crust float on?
the silicate mantle
how much of the Earth’s volume does the mantle made up?
~90% of the earth’s volume
what is the state of the mantle?
semi-molten/liquid
why do tectonic plates move?
as the upper mantle is semi molten, the thermal convection currents rise and fall, driving the sideways motion of the tectonic plates
how hot is the outer core of the earth?
~5000 K
what materials is the outer core made out of?
liquid iron + nickel
how is the earth’s magnetic field created?
currents of charged particles that flow in the outer core
what is the state of the inner core?
solid
what is the temperature of the inner core?
~5500 K
why is the inner core solid?
high pressure prevents the iron and nickel melting
what is latitude measured in?
degrees north or south of the equator.
how is longitude measured?
east or west of the prime meridian
where is the prime meridian?
In 1884, the meridian passing through the Observatory of Greenwich was globally adopted as the zero of longitude
how much is the earth’s polar axis tilted by?
23.5* to the vertical
when does the sun lie directly over the equator2
21st june; this is the summer solstice
when does the sun lie directly over the tropics of Capricorn (23.5*S)?
21st December; this is also the winter solstice.
what are the Arctic and Antarctic Circles?
The Arctic and Antarctic Circles represent the most northen (66.5N) and southern (66.5S) latitudes.
why is the atmosphere important?
the atmosphere:
- provides us with oxygen to breath
- absorbs harmful solar UV and X-radiation
- Regulates our planet’s temperature to mean 15*C
- Protects us from most meteoroid strikes
what are the drawbacks for the atmosphere?
The drawbacks of the atmosphere are:
- The sky is blue restricting observations to night time
-Light is scattered by oxygen and nitrogen molecules in our air: most scattering occurs at shortest (blue) wavelengths so the sky is blue
- air is in the atmosphere and is continuously in turbulent motion.
Different densities of air ride and fall on a variety of scales causing light to react and change direction as it passes through the different layers making the stars “twinkle”
what difficulties are there from observations for astronomers?
some major problems are:
- skyglow is the rusty orange haze caused by lights near urban communities
- Local glare from things like streetlights ruin our dark adaptation
what are the two most common elements in the Earth’s core?
Iron and Nickel
What are the two most common elements in the earth’s crust?
Silicon and oxygen
what evidence is there that proves that earth is a sphere?
- satellites orbit the earth
- ships disappear over the horizon
- the earth casts a curved shadow during an eclipse
- aircraft fly in arcs (not straight lines)
- images of the earth from space
what is the polar axis of the earth?
the line around which the earth rotates
how much is the earth’s axis inclines to the ecliptic?
66.5*
which direction does Right Ascension move?
eastwards
