PETROLOGY (GROUP 6)

physical classification

• FOCUSES ON OBSERVABLE CHARACTERISTICS

• DIFFERENTFROM CHEMICAL OR MINERAL CLASSIFICATION

• HELPS IN IDENTIFYING ROCK TYPES AND ORIGINS

key physical properties

• texture

• grain size

• color

• hardness

• porosity

• permeability

• structure

texture

refers to the size, shape and arrangement of grains or crystals

grain size

tell us about formation speed or environment

color

it indicates mineral content

hardness

• resistance to scratching

  • measured on mohs scale (1-10)

porosity

• % of empty space between grains

• high: sandstone

• low: granite, basalt

permeability

• ability of fluids to pass through

• depends on porosity and connectivity

• important in groundwater flow

structure

Large-scale features:

• Bedding (sedimentary)

• Foliation (metamorphic)

• vesicles (igneous/volcanic)

silliceous

formed from the accumulation and compaction of silica-rich sediments, such as quartz sand or the remains of silica-secreting organisms like diatoms and radiolarians.

argillaceous

Formed from the deposition and lithification of fine grained sedimentary materials, typically clay particles carried by water and deposited in lowenergy.

calcareous

formed through the accumulation and cementation of calcium carbonate-rich sediments, commonly in warm, shallow marine environments with abundant carbonate-producing organisms.

rock cycle

• igneous rocks

• sedimentary rocks

• metamorphic rocks

igneous rocks

• formed when magma or lava, cools and hardens

• formed by cooling

sedimentary rocks

• over time, weather like ran, wind, and ice breaks down existing rocks into tiny particles

• formed by weathering and erosion

metamorphic rocks

• sometimes, rocks get buried deep in the earth, where they’re exposed to intense heat and pressure

• formed by heat and pressure

sedimentation

Sediments are deposited in layers, often in basins or on land, and over time, they can be compacted and cemented together, forming sedimentary rocks through a process called lithification

cooling and hardening

As hot, molten rock rises to the surface, it undergoes changes in temperature and pressure that cause it to cool, solidify, and crystallize

metamorphism

This process involves the transformation of existing rocks into metamorphic rocks dueto heat,pressure, or chemical reactions deep within the Earth's crust.

weathering and erosion

Weathering (the breaking down of rocks) and erosion (the transport of rock fragments) by wind, water, and ice, are key processes in the rock cycle. These processes transform existing rocks into smaller particles called sediments.

melting

Under certain conditions, rocks can melt and become magma, restarting the cycle.