Geology 101: Lithosphere and Mineral Composition

Lithosphere

  • The most significant part of the outer crust of the Earth is the Lithosphere.
      - Definition: The term "Lithosphere" literally means "the sphere of rock".
      - Extends down to a depth of 16 km from the surface.
      - Composition: 95% of the materials found in the Earth's crust consist of rocks.

Rocks and Minerals

  • Definition of Rocks: Rocks are comprised of minerals, which are typically found in a solid state.
      - Mineral Composition: Each mineral usually contains two or more elements.
      - The entirety of the Earth is made up of various elements.

  • Mineral Diversity: There are approximately 2,000 different minerals, but only 12 are recognized as common throughout the Earth.
      - These common minerals are referred to as rock-formers.

Abundant Elements in the Earth's Crust

  • The common minerals are primarily made up of the 8 most abundant elements:
      - Iron (Fe) - 35%
      - Oxygen (O) - 30%
      - Silicon (Si) - 15%
      - Magnesium (Mg) - 13%
      - Nickel (Ni) - 2.4%
      - Sulphur (S) - 1.9%
      - Calcium (Ca) - 1.1%
      - Aluminium (Al) - 1.1%
      - These elements together account for about 99% of the total mass of the Earth.

  • Key Bulk Elements:
      - The four primary elements: iron, oxygen, silicon, and magnesium, constitute approximately 93% of the total mass of the Earth.

Earth's Crust vs. The Whole Earth

  • The constitution of the Earth's crust differs from that of the Earth as a whole.
      - The eight most abundant elements in the Earth's crust are:
        - Oxygen (46%)
        - Silicon (28%)
        - Aluminium (8%)
        - Iron (6%)
        - Magnesium (4%)
        - Calcium (2.4%)
        - Potassium (2.3%)
        - Sodium (2.1%)

Minerals: Overview

  • Definition of Minerals: Minerals are chemical substances found in nature that can either be elemental or compounds.
      - Types of Minerals:
        - Metallic Minerals: Examples include iron, copper, lead, and gold.
        - Non-Metallic Minerals: Examples include gypsum, quartz, and mica.

  • Formation of Rocks: Minerals are organized to form rocks.

Important Mineral Groups

  1. Silicates:
       - One of the most important groups of rock-forming minerals.
       - Comprises about 87% of the minerals in the Earth's crust.
       - Key minerals in this group include:
         - Quartz: Composed of silicon and oxygen.
         - Feldspar
         - Ferromagnesium minerals.