- Internal Structure of the Earth
- External Structure of the Earth
The structure of the earth consist of a series of layers both internal and external, these layers includes
The evidence used to study the earth’s interior are
- Outermost layer of the earth
- Made of soils and other loose deposits of sand
- The dominant rocks are granites.
- Extends from 16-24 km thick but where mountains occurs it can have a thickness of 70km.
- Has 2 layers; continental crust and oceanic crust.
- Also called continental crust
- Made of light colored rocks
- Called sial because it’s made up of silica and aluminum.
- It is lighter( having a density of 2.7 grams/cc) this makes it float on the oceanic crust.
- Also called oceanic crust
- Mainly made of basaltic rocks which are brittle.
- Called sima because it is made of silica and magnesium.
- It has a density of 2.8-3.0gm/cc
- It is thin ranging from 6km-10km in thickness.
Mohorovicic Discontinuity (Moho)
- A definite zone of discontinuity between the crust and the mantle.
- Was discovered by Dr. Andrija Mohorovicic in 1909.
- On average its about 2900km thick
- Its composed of silicate rocks rich in iron and magnesium.(olivine)
- It has an average density of 3.0-3.3gm/cc
- Its divided into two layers namely; upper mantle and lower mantle
- Rocks are more elastic than those of sima.
Temperature is about 1000â¦c.
- Rocks are like very viscous liquid.
- Temperature ranges between 1000â¦c to 3000â¦c.
- A definite zone of discontinuity between mantle and core
- Its has a radius of 3470km
- Its divided into two layers namely; inner core and outer core.
- Its has an average density of 12.0gm/cc
- Composed of hot molten rocks
- Made up of nickel and iron
- Temperatures are up to 3700â¦c.
- A solid mass of iron
- Its has a density of 16 -17gm/cc.
- Temperatures are estimated to be 3700â¦c to 5500â¦c.
- Due radio-active decay causing most of the heating. The decay of the radio-active material causes explosion occasionally releasing a lot of heat through nuclear fission
- Due to great pressure as a result of overlying crustal materials, this intense pressure generates a lot of heat inside the earth.
- The earth stills retains the original heat which it had before its started cooling, during cooling the outer parts cool faster than the interior trapping the original heat inside it
- It’s a layer of transparent and odourless gases held to the earth by its gravitational pull.
- The earth revolves with it because its held onto it by gravity
- It’s about 330km thick.
Composition of the Atmosphere
- Gases-exist as a mixture
- Smoke particles
- Dust particles
The Structure of the Atmosphere
It’s divided into 4 layers/zones namely: troposphere, stratosphere, mesosphere and thermosphere.
Lowest layer of the atmosphere
- Contains most of the atmospheric water vapour or clouds
- Extends 8km at the poles and 13km at the equator
- Temperature decreases with increase in altitude at a rate of 6.50 c per 1000m (normal lapse rate)
- Pressure falls with increase in height
- The speed of wind increases with increase in height
- Contains dust particles
- There is a zone of transition between troposphere and stratosphere called tropopause,
In these zone there is no change in temperature with increase in height, hence experiences zero lapse rate
Extends from the tropopause to a height of 30km
- The temperature increases with increasing altitude , this is called the negative lapse rate, the temperature increase is caused by the concentration of ozone gas
- Has ozone layer which absorbs harmful ultraviolet radiation.
- Winds are light in the lower but increase with height.
- The atmospheric pressure continues to fall as the air is dry
- Air is calm so it’s used by passenger jets
- Limited amounts of water vapour
There is a zone of transition between stratosphere and mesosphere called stratopause.
Extends from 50-80 km
- Temperature decreases with increasing altitude, this is called positive lapse rate, the decrease in temperature is because there is no water vapour or ozone gases to absorb the incoming terrestrial radiation
- Its has the lowest temperature ranging -900c
- Has very strong winds that at times reaches 3000km/hr
There is a zone of transition between mesosphere and thermosphere called mesopause .which is an inversion layer.
Extends from 90-120km
- High radiation is present.
- Temperature rapidly increases with height, this is due to the over concentration of atomic oxygen which absorb incoming ultra-violet radiation
- Temperature reaches to a high of over 15000c
- The pressure is very low.
- Gases and molecules in this layer exist as ions due to high radiation.
- Thermosphere has no definite top but merges gradually into the outermost part of the atmosphere called exosphere.
- Exosphere consists of rare gases like hydrogen and helium.
- Beyond the atmosphere there is the outer space.
- Outer space is the universe beyond the atmosphere in which other planets and stars exist.
Composition of the Atmosphere
The atmosphere is composed of the following gases
- Nitrogen 78%
- Oxygen 20%
- Water vapour 1%
- Argon 0.94%
- Carbon dioxide 0.03%
- Inert gases such as neon, krypton and xenon are found in traces (negligible percentages)
Significance of the Atmosphere
- Animals and plants breathe in from it oxygen for respiration.
- Plants use carbon dioxide from it for photosynthesis.
- Water vapour in the atmosphere condenses to form clouds which give us rain.
- Ozone layer in the stratosphere shields us from ultraviolet radiation which may cause cancers.
- Carbon dioxide and methane in the atmosphere cause global warming through the green house effect.
- Part of the earth’s surface covered by water masses e.g. oceans, seas, lakes, rivers and even underground water. It comprises 73% of the earth’s surface area.
- The lower atmosphere, hydrosphere and the upper part of the earths crust are called biosphere meaning the sphere of the earth in which organic liofe exists.