Petrology: The scientific study of rocks.
Three Main Types:
Sedimentary: Formed by the accumulation of sediments.
Igneous: Result from the solidification of molten rock (magma).
Metamorphic: Pre-existing rocks that have been altered through heat and pressure.
Processes: A web of processes that describes how each of the three major rock types (igneous, sedimentary, metamorphic) forms and breaks down.
Key Processes in Rock Cycle:
Weathering: Breakdown of rocks at the Earth’s surface.
Erosion: The movement of sediments.
Melting: Transition of solid rock to molten rock (magma).
Cooling: Solidification of magma into igneous rock.
Compaction: Process where sediments are squeezed together.
Cementation: Minerals precipitate from water and bond sediment particles together.
Definition: Rocks formed from the cooling and solidification of magma, derived from the Latin word ignis meaning "fire rock".
Types of Igneous Rocks:
Intrusive Igneous Rocks:
Formed from magma that solidifies beneath the Earth's surface.
Often exhibit large visible crystals due to slow cooling (e.g., granite, diorite).
Also known as Plutonic rocks.
Extrusive Igneous Rocks:
Formed when magma reaches the surface during volcanic eruptions.
Typically have small crystals due to rapid cooling (e.g., basalt, obsidian).
Felsic Minerals: Characterized by high levels of feldspar and silica.
Mafic Minerals: Composed mainly of magnesium and ferrous iron.
Examples:
Basalt
Granite
Gabbro
Pumice
Also known as "derived rocks" created from the accumulation of sediments.
Definition: Fragments of rock broken down by weathering.
Classification (from smallest to largest):
Clay
Silt
Sand
Pebble
Cobble
Boulder
Refers to the movement of solid particles by agents such as wind, water, or ice.
Process of laying down sediments that are carried by wind, water, or ice.
Process transforming loose sediment into solid rock.
Key Processes:
Compaction: Sediments are pressed together under pressure.
Cementation: Minerals fill the spaces between sediment grains to bond them.
Clastic Sedimentary Rocks: Composed of particles from other rocks.
Biogenic Sedimentary Rocks: Formed from biological material.
Chemically Precipitated Sedimentary Rocks: Formed when minerals precipitate from solution.
Formed from existing rocks (igneous, sedimentary, or earlier metamorphic) altered by heat, pressure, or mineral-rich fluids.
This transformation occurs through a process called metamorphism.
Contact Metamorphism: Occurs when rocks are heated by nearby magma.
Regional Metamorphism: Changes that happen over large areas under high pressure and temperature.
Dynamic Metamorphism: Associated with high shear stress, often near fault zones.
Heat: Causes chemical reactions and mineral changes.
Pressure: Can be directional or uniform, leading to changes in rock texture.
Chemically Active Solutions: Fluids can facilitate metamorphic reactions.
Foliated Rocks: Have a layered or banded appearance (e.g., slate, schist, gneiss).
Characterized by aligned minerals/planes of weakness within the rock.
Non-Foliated Rocks: Have a more uniform texture; not layered (e.g., marble, hornfels).
Typically contain crystals of similar sizes throughout.
Slate: Fine-grained, foliated, derived from shale.
Schist: Medium to coarse-grained, with visible minerals.
Marble: Metamorphosed limestone.
Gneiss: Alternating bands of light and dark minerals.