■ SOURCES OF EARTH’S HEAT [PART 1]
#interiorofearth
1. Radioactive decay
◇ The high temperature below the crust is attributed to the disintegration of the radioactive substances.
◇ The nuclear decay happens primarily in the crust and the mantle.
◇ Scientists believe that uranium could become sufficiently concentrated at the base of Earth’s mantle to ignite self-sustained nuclear fission, as in a human-made reactor.
◇ The new measurements suggest radioactive decay provides more than half of Earth's total heat.
■ SOURCES OF EARTH’S HEAT [PART 2]
#interiorofearth
2. Primordial heat
◇ Heat left over from Earth's formation known as the primordial heat.
◇ Primordial heat is the kinetic energy transferred to Earth by external impacts of comets and meteorites and the subsequent effects (friction caused by sinking of heavy elements like Fe, rising light elements like Si) and latent heat of crystallisation released as the core solidified.
■ SOURCES OF INFORMATION ABOUT THE INTERIOR. [ PART 1]
#interiorofearth
□ DIRECT SOURCES
◇ Deep earth mining and drilling reveal the nature of rocks deep down the surface.
◇ But as mining and drilling are not practically possible beyond a certain depth, they don’t reveal much information about the earth’s interior.
◇ Mponeng gold mine (deepest mine in the world) and TauTona gold mine (second deepest mine in the world) in South Africa are deepest mines reaching to a depth of only 3.9 km.
◇ And the deepest drilling is only about 12 km deep hole bored by the Soviet Union in the 1970s over the Kola Peninsula.
◇ Volcanic eruption forms another source of obtaining direct information.
■ SOURCES OF INFORMATION ABOUT THE INTERIOR. [ PART 2]
#interiorofearth
INDIRECT SOURCES.
□ Seismic waves
◇ They are the most important source available to understand the layered structure of the earth.
◇ The velocity of seismic waves changes as they travel through materials with different elasticity and density.
□ Meteorites
◇ Meteorites and Earth are born from the same nebular cloud. Thus, they are likely to have a similar internal structure.
□ Gravitation
◇ The gravitation force (g) is not the same at different latitudes on the surface. It is greater near the poles and less at the equator.
◇ This is because of the distance from the centre at the equator being greater than that at the poles.
◇ The gravity values also differ according to the mass of material.
□ Magnetic field
◇ The geodynamo effect helps scientists understand what's happening inside the Earth's core.
◇ Shifts in the magnetic field also provide clues to the inaccessible iron core.
■ THE STUDY OF EARTH'S INTERIOR IS ESSENTIAL :
#interiorofearth
◇ to understand the earth’s surface :-
• Many different geological processes shape the Earth's surface. The forces that cause these processes come from both above and beneath the Earth's surface.
◇ to understand Geophysical phenomenon like volcanism, earthquakes
• The forces that cause catastrophic events like earthquakes, volcanic eruptions come from deep below the earth’s surface.
◇ to understand the earth’s magnetic field
• Earth’s magnetic field is a result of convection currents in the outer core of the earth. Life on earth would not have been possible if not for the earth’s magnetic field which protects the earth’s atmosphere from the harmful solar wind.
◇ to understand the internal structure of various solar system objects.
◇ to understand Evolution and present composition of the atmosphere.
