Temperature
Rise in temperature with increase in depth is observed in mines and deep wells.
These evidences along with molten lava erupted from the earth’s interior, support
that temperature increases towards the centre of the earth. The different observations
show that the rate of increase of temperature is not uniform from the surface
towards the earth’s centre.
It is faster at some places than at others. In the beginning this increase is at an
average rate of 10C for every 32 metres increase in depth. At such a constant rate
of increase in temperature, at 10 km depth, the temperature will be approximately
3000C and at 40 km depth it will be 12000C. At this rate, earth’s interior should
be in a molten state. Yet it is not so because the rocks buried under the pressure of
several km thickness of overlying rocks melt at higher temperature than similar
rocks at the surface. A basaltic lava rock which melts at 12500C at the surface will
melt at 14000C at 32 km depth. The extra heat required for melting is produced
by radioactivity. It is the result of breakdown of atomic nuclei of minerals emitting
radiant energy in the form of heat from the rocks. .
The behaviour of earthquake waves is another evidence for this phenomenon.
They further confirm that the composition of different layers is as variable as is the
rate of change of temperature. While in the upper 100 km, the increase in temperature
is at the rate of 12°C per km, in the next 300 km it is 20°C per km but is
only 100C per km below it. Thus the rate of increase of temperature beneath the
surface decreases towards the centre. The temperature at the centre is estimated
to lie somewhere between 3000°C and 50000C.Such a high temperature inside
the earth may be due to chemical reactions under high pressure conditions and
disintegration of radio active elements.
These evidences along with molten lava erupted from the earth’s interior, support
that temperature increases towards the centre of the earth. The different observations
show that the rate of increase of temperature is not uniform from the surface
towards the earth’s centre.
It is faster at some places than at others. In the beginning this increase is at an
average rate of 10C for every 32 metres increase in depth. At such a constant rate
of increase in temperature, at 10 km depth, the temperature will be approximately
3000C and at 40 km depth it will be 12000C. At this rate, earth’s interior should
be in a molten state. Yet it is not so because the rocks buried under the pressure of
several km thickness of overlying rocks melt at higher temperature than similar
rocks at the surface. A basaltic lava rock which melts at 12500C at the surface will
melt at 14000C at 32 km depth. The extra heat required for melting is produced
by radioactivity. It is the result of breakdown of atomic nuclei of minerals emitting
radiant energy in the form of heat from the rocks. .
The behaviour of earthquake waves is another evidence for this phenomenon.
They further confirm that the composition of different layers is as variable as is the
rate of change of temperature. While in the upper 100 km, the increase in temperature
is at the rate of 12°C per km, in the next 300 km it is 20°C per km but is
only 100C per km below it. Thus the rate of increase of temperature beneath the
surface decreases towards the centre. The temperature at the centre is estimated
to lie somewhere between 3000°C and 50000C.Such a high temperature inside
the earth may be due to chemical reactions under high pressure conditions and
disintegration of radio active elements.
Pressure
The pressure also increases from the surface towards the centre of the earth due
to huge weight of the overlying rocks. Therefore in deeper portions, the pressure
is tremendously high. The pressure near the centre is considered to be 3 to 4
million times the pressure of atmosphere at sea level. At high temperature, the
material beneath will melt towards the central part of the earth. This molten material
under tremendous pressure conditions acquires the property of a solid and is
probably in a plasma state
to huge weight of the overlying rocks. Therefore in deeper portions, the pressure
is tremendously high. The pressure near the centre is considered to be 3 to 4
million times the pressure of atmosphere at sea level. At high temperature, the
material beneath will melt towards the central part of the earth. This molten material
under tremendous pressure conditions acquires the property of a solid and is
probably in a plasma state
Density
Due to increase in pressure and presence of heavier materials towards the earth’s
centers, the density of earth’s layers also goes on increasing. Obviously the materials
of the innermost part of the earth are very dense as already stated.
centers, the density of earth’s layers also goes on increasing. Obviously the materials
of the innermost part of the earth are very dense as already stated.
No comments:
Post a Comment