Internal Energy of Earth: Sources, Flow, and Convection Currents

Internal Energy

Source

Two primary energy fields influence Earth: magnetic and gravitational. Earth receives solar energy and releases heat and mechanical energy from within. Two sources contribute to Earth's internal heat:

• Heat released from radioactive fission processes of minerals.
• Primordial heat originating from two sources:
  • Impact energy during Earth's accretion, transformed into heat and preserved within the planet.
  • Energy released during the formation of Earth's core.

Geothermal Gradient and Degree

Geothermal Gradient: The temperature increase of 1°C for every 33 meters of depth.

Geothermal Degree: The depth required for the temperature to increase by 1°C.

Geothermal Energy and Volcanoes

Geothermal energy, evident in volcanoes, has two origins:

• Deep sources, uniform across the globe.
• Cortical sources, varying based on radioactive element content, influencing lithospheric plate dynamics and volcanic phenomena.

Materials ejected from volcanoes can be:

• Gaseous
• Liquid (lava flows)
• Solid (ash)

Elastic Energy of Earthquakes

Rocks undergo three types of strain: elastic, plastic, and brittle. According to the elastic rebound theory, rocks accumulate elastic deformation and tension until exceeding their strength, fracturing and releasing energy, creating a fault. This released elastic energy causes earthquakes. Not all energy is released as seismic waves; some converts to heat due to friction.

Three types of forces cause earthquakes:

• Horizontal pressure, causing reverse faults.
• Horizontal tension, causing normal faults.
• Horizontal stress and strain, causing strike-slip faults.

Heat Flow

Heat flow is the amount of heat energy reaching Earth's surface from its interior through conduction. Rocks are poor heat conductors. Heat flow is expressed as: Q = K * dT / dZ.

Convection Currents

Since rocks are poor conductors, conduction isn't the sole heat propagation mechanism. Convection, where heated fluid expands, rises, cools, and descends, also plays a role. This occurs in the atmosphere, hydrosphere, and Earth's interior.

Convection models include:

• Single convection system.
• Layered system with two separate mantle convection levels.
• Hybrid model: Two levels with potential interaction. Ascending plumes from the lower mantle contribute to continental fragmentation (hot spots). Descending branches from the upper mantle involve lithospheric sliding from ridges and subduction.

Volcanoes form as plates move over hot spots, creating chains of volcanoes or islands.