Earth's Origin and Structure

Origin and Structure of the Earth

• Earth is uniquely supportive of life, primarily due to its abundance of water.
• Approximately 70% of Earth’s surface is covered by water.
• The planet has an optimal distance from the sun, contributing to a suitable climate.
• The atmosphere acts as a shield protecting life from harmful solar radiation.
• Earth possesses an ozone layer that absorbs harmful rays, safeguarding organisms.

Subsystems of the Earth

• The four subsystems are Atmosphere, Biosphere, Geosphere, and Hydrosphere.
• Atmosphere: Gaseous layer above Earth composed of 78% nitrogen and 21% oxygen, with trace gases like carbon dioxide and argon.
• Ozone in the atmosphere plays a crucial role in protecting living organisms.
• Biosphere: Zone where all life exists, influencing climate via photosynthesis, exchanging oxygen and carbon dioxide.
• Geosphere: Solid Earth, consisting of the core, mantle, and crust. Interior temperature increases with depth, forming the geothermal gradient (15-30°C/km for the first 100 km).
• Hydrosphere: Water component including oceans, glaciers, groundwater, and inland water.
• Matter and energy flow across the boundaries of these subsystems, indicating their interconnectedness.
• Examples of interconnections include waves eroding rocks (hydrosphere-geosphere) and carbon dioxide dissolving in oceans (atmosphere-hydrosphere).

Minerals

• Minerals are the fundamental building blocks of rocks.
• Characteristics include:
  • Naturally occurring: Formed through Earth’s natural processes.
  • Inorganic: Not derived from organisms.
  • Homogeneous solid: Definite volume and rigid shape.
  • Definite chemical composition: Can be expressed as a chemical formula.
  • Orderly crystalline structure: Atoms arranged in a repeating pattern.
• Properties of minerals:
  • Streak: Color in powdered form.
  • Hardness: Resistance to scratching.
  • Cleavage: Tendency to break along flat surfaces.
  • Luster: Reflection of light from the mineral's surface.

Rocks

• Rocks are naturally occurring solid aggregates of one or more minerals.
• Most rocks consist of mixtures of different minerals, bonded chemically.
• Petrology is the study of rocks.
• Igneous Rocks:
  • Komatiite: A rare ultramafic rock, very fine-grained, believed to be abundant in Earth's mantle.
  • Ultramafic magma forms rocks with a phaneritic texture.
  • Types of igneous rocks:
    • Extrusive/Volcanic: Forms from lava cooling quickly at the surface, resulting in fine-grained crystals.
    • Intrusive/Plutonic: Cools slowly beneath the surface, leading to large, coarse-grained crystals.
• Texture refers to the appearance of a rock based on the size, shape, and arrangement of mineral crystals.