Earth’s Crust: Minerals, Rocks, and Geological Processes
Earth’s Crust: Minerals and Rocks
Relief refers to the surface irregularities of the Earth’s crust.
- Land Relief: Above sea level.
- Submerged Relief: Extended under sea level.
Minerals: Composition and Characteristics
Minerals are chemical elements or compounds formed by natural processes, with the following characteristics:
- They are solid.
- They have a fixed chemical composition.
- They originate from natural processes.
- They consist of crystalline material.
Mineraloids consist of amorphous material whose atoms do not have an orderly distribution.
Mineral Crystal Formation
Mineral crystals originate in a crystallization process through mechanisms such as:
- Chemical Precipitation
- Solidification: Formation of crystals from cooling and consolidating magma.
- Sublimation: Change from gas to solid.
- Recrystallization: Increase in size and reorientation of minerals.
Properties of Minerals
- Density: Ratio of a mineral’s mass and volume.
- Hardness: Resistance of a mineral to being scratched.
- Exfoliation: Tendency of certain minerals to break easily when struck.
- Color: Depends on the light absorbed or reflected by the mineral.
- Brightness: How a mineral surface reflects light.
- Diaphaneity: Degree of transparency of a substance.
Rock: A set of minerals created in a terrestrial environment or naturally.
Endogenous Rocks
Endogenous rocks originate from geological processes within the geosphere. Types include:
- Metamorphic Rocks: Formed by metamorphism, the transformation of minerals in a rock due to temperature and pressure changes.
- Magmatic Rocks: Originate from magmas.
Exogenous or Sedimentary Rocks
Exogenous or sedimentary rocks originate in exogenous geological processes. Sedimentary rocks originate from the transformation of sediments deposited in sedimentary basins, forming strata.
Classification of Sedimentary Rocks
- Detrital: Formed by the accumulation of debris, particles, and fragments resulting from the erosion of rock surfaces: clusters (large), sands and sandstones (medium), clays and claystones (very fine).
- Non-Detrital: Sediment originates from precipitation: limestone (sediment originated from precipitation), dolomite (calcium carbonate formed and have a crystalline appearance), evaporite (formed when there is high evaporation of water).
Metamorphism
Solid-state process of metamorphism of rocks under great pressures and temperatures, favoring the arrangement of atoms in minerals. It can be:
- Heat: Produced by high temperatures near magma. Some magma forms a halo of metamorphic rocks.
- Dynamothermal: Located in broad areas where two lithospheric plates meet, called regional metamorphism.
Classification of Metamorphic Rocks
- Non-Foliated: Marble and quartzite.
- Foliated: Slate and shale.
Magmatism
Magma: Molten mass of mineral crystals containing solids and gases. It tends to rise to the surface due to high pressures. Over time, the magma cools and forms igneous rocks.
- Strengthening the Magma: Inside the crust, the magma cools slowly in a deep zone, forming large crystals. These are plutonic rocks.
- On the Surface: Magmas that reach the surface quickly lose gases and become lava, forming volcanic rocks.
Dynamics of Rocks
Processes:
- Gliptogenesis: Exogenous geological processes due to the action of surface geological agents that alter and erode rocks.
- Lithogenesis: Set of processes that form the different types of rocks.
- Orogeny: Endogenous geological processes that form ridges.