Earth Sciences: Structures, Layers, Movements, and Phenomena

Posted on Mar 9, 2025 in Geology

Earth Sciences Questionnaire

The Earth’s structure, from the center to the periphery, consists of a series of layers:

Internal Structures

  • Core: Its discovery is attributed to the observation of a shadow recorded on the Earth’s surface between 103 and 143 degrees.
  • Mantle: A solid layer approximately 2900 km thick, composed of molten material in its outer part and becoming stronger towards the Earth’s center.
  • Crust: The outermost layer of the Earth, with properties distinct from the underlying mantle. It consists of two different layers:
    • Sial: Primarily composed of silicon and aluminum compounds.
    • Inmates: Composed of magnesium silicate minerals, resembling gabbro, chasm, and basalt.

External Structures

  • Hydrosphere: Water in solid form (ice) and liquid form (oceans, seas, rivers, and lakes).
  • Lithosphere: Situated between the hydrosphere and atmosphere, its major constituents are granite and basalt, with a peak thickness of 5-70 km.
  • Atmosphere: Divided into:
    • Ionosphere: Located between 50-400 km altitude, this layer experiences the highest levels of solar radiation.
    • Stratosphere: Located between 10-50 km altitude, it contains the highest concentration of ozone.
    • Troposphere: Located between the land surface and 10 km altitude, it contains the highest percentage of essential gases for life, such as oxygen.
  • Biosphere: The largest of the external layers, primarily composed of carbon, hydrogen, and oxygen compounds.

Earth’s Shape

Since ancient times, it has been known that the Earth is round. Observers near the sea or a lake notice boats disappearing over the horizon, indicating the curvature of the ocean surface and land.

Earth’s Position

The Earth’s rotation establishes a rotation axis. The intersection of this axis with the Earth’s surface represents the two poles. Latitude is measured in degrees north and south of the Equator, determined by celestial observation.

Earth’s Measurement

To determine the Earth’s dimensions, including its radius and surface area, accurate volume measurements begin with measuring its circumference.

The flattening of the globe is estimated by the difference between the equatorial radius (6378.5 km) and the polar radius (6356.5 km), which is 22 km. This difference is only 0.33% (0.0033) of the equatorial radius, making it imperceptible from the ground.

Earth’s Movements

  • Rotation: The Earth rotates around its polar axis in 23 hours, 56 minutes, and 09 seconds, resulting in the day as a unit of time, the succession of day and night, and the flattening of the poles and bulging of the Equator.
  • Translation: The Earth completes a full translation around the Sun in 365 days, 5 hours, and 46 seconds, moving on an orbit located in an imaginary plane called the ecliptic.

Tides

Tides are the ascending and descending movements of water bodies (seas and oceans) due to gravitational attraction. The side of the Earth facing the Moon experiences a stronger gravitational pull, resulting in high tides, while the opposite side experiences low tides.

Eclipses

  • Solar Eclipse: Occurs when the Moon is positioned between the Earth and the Sun in a straight line.
  • Lunar Eclipse: Occurs when the Sun and Moon are on opposite sides of the Earth, with an angle of 180 degrees.