Earth as an Operational System

Earth as an Operational System

• Earth is comprised of interacting spheres: Geosphere (solid Earth), Atmosphere (gas), Hydrosphere (water), Cryosphere (frozen water), and Biosphere (life).
• Earth materials include minerals, rocks, soil, rock fragments, fossil fuels, and water, encompassing all Earth spheres.
• The lithosphere is the outermost rigid part of the Geosphere, incorporating the crust and upper mantle, forming tectonic plates.

Defining a Mineral

• Geological "mineral" differs from nutritional/pharmaceutical definitions.
• A geological mineral is: naturally occurring, inorganic, solid at room temperature, has an orderly internal crystalline structure, and a definable chemical composition.
• Exceptions exist: water and mercury, though liquid at room temperature, are classified as minerals.
• The International Mineralogical Association (1985) amended the definition to: an element or chemical compound that is normally crystalline and formed by geological processes.
• Mineraloids are non-crystalline substances (amber, pearl, opal, obsidian).

Building Blocks of Rock

• A rock is a solid made of one or more minerals/mineraloids.
• Rock types (based on mineral composition/formation): igneous (molten), sedimentary (weathering products), metamorphic (reorganization).
• Mineral identification is crucial for understanding rock formation and history.

"Big Ten" Minerals

• Geologically important common minerals identified as "The Big Ten": olivine, augite, hornblende, biotite, calcium-rich plagioclase, sodium-rich plagioclase, potassium-rich feldspar, muscovite, quartz, calcite.
• Thousands of other minerals exist, but these are commonly used for rock identification.

Mineral Chemistry

• Matter is made of atoms with subatomic particles (protons, neutrons, electrons).
• Atomic number is the number of protons.
• Atomic mass is the number of protons and neutrons.
• Isotopes are atoms of the same element with different numbers of neutrons.

Elements in Earth's Crust

• Eight elements are abundant in the Earth's crust.
• Minerals form through chemical bonding between these elements.

Chemical Bonding and Ions

• Atoms bond to achieve stable electron configurations.
• Loss/gain of electrons creates charged ions (cations are positive and anions are negative).
• Ionic bonds form from attractive forces between oppositely charged ions.

Formation of Silicate Minerals

• Formation from cooling magma (molten rock).
• Bowen's Reaction Series diagrams show mineral formation order during cooling.
• The discontinuous branch shows minerals with varying iron/magnesium content (olivine, pyroxene, amphibole, biotite).
• The continuous branch shows plagioclase feldspar (calcium-rich to sodium-rich).

Other Mineral Groups

• Calcite (carbonate) forms through:

  • Biomineralization (organism activity)
  • Precipitation (chemical solution)
  • Evaporation (water loss).

• Clay minerals are sheet silicates formed by weathering of other minerals. -Metamorphic minerals form from pre-existing rocks (e.g., garnet).

• Iron oxides (e.g., hematite, magnetite) and rust are formed through the reaction between oxygen and iron.

• Halides (e.g., halite, sylvite) indicative of evaporating water.

• Sulfides (e.g., pyrite, chalcopyrite, galena, sphalerite) and their significance in historical geology.

• Sulfates (e.g., gypsum) often contain water in their structure, indicating evaporative environments.

• Phosphates (e.g., apatite) often found in biological material.

• Native elements (e.g., gold, silver, copper) occur in pure/nearly pure state.