Igneous Rocks and Textures

Igneous Rocks

• Obsidian is a common natural glass with high silica content, characterized by a dark color due to metallic ions.
• Pumice forms when gas escapes from molten rock, creating a frothy grey mass.
• Andesite is a medium-gray, fine-grained volcanic rock with porphyritic textures, containing light plagioclase and elongated amphibole phenocrysts.
• Diorite is the intrusive equivalent of andesite, similar to granite but lacking visible quartz and having more dark silicates.
• Basalt, the most common extrusive igneous rock, is dark green to black with a fine-grained texture, made up of pyroxene, olivine, and plagioclase; its intrusive equivalent is gabbro.
• Bowen’s Reaction Series illustrates the order of mineral crystallization based on temperature as magma cools.
• Magmatic differentiation alters the chemistry of magma as certain minerals crystallize and sink, changing the composition of remaining melt.

Igneous Textures

• Fine-grained igneous rocks form at the surface or in small intrusive masses with rapid cooling, featuring crystals only visible under a microscope.
• Coarse-grained igneous rocks result from slow crystallization of large magma masses at depth, featuring intergrown crystals.
• Porphyritic texture occurs when minerals crystallize under varying conditions, containing larger crystals (phenocrysts) within a fine-grained matrix (groundmass).

Sedimentary Rocks

• Sedimentary rocks form from weathered materials transported by erosion and lithified by compaction and cementation.
• "Sedimentary" derives from the Latin "sedimentum," reflecting the settling of solid materials from fluids.

Detrital Sedimentary Rocks

• Composed of solid particles from weathered rocks, primarily clay minerals and quartz, making up the most durable products of chemical weathering.
• Classified by particle size to provide insight into depositional environments.

Chemical & Biochemical Sedimentary Rocks

• Form from ions in solution that precipitate out due to physical processes or through organic activity creating shells.
• Influence of organisms contributes to sediment formation and sedimentary rock characteristics.

Weathering Processes

• Unloading and sheeting result in concentric slabs breaking from rock masses upon erosion, forming exfoliation domes.
• Bioturbation refers to the actions of organisms impacting soil structure.
• Spheroidal weathering rounds angular fragments through selective weathering at corners.

Soil Characteristics

• Soil structure, comprising clumps called peds, influences erosion, porosity, and permeability. Variants include platy, prismatic, blocky, and spheroidal.
• Residual soils develop from bedrock, while transported soils originate from loose sediments.
• Soil formation is influenced by parent material, time, climate, organisms, and topography, which collectively determine fertility and drainage properties.

Streamflow and Sediment Transport

• Sediment load in streams consists of dissolved load (carried by groundwater), suspended load (largest portion and visible muddy appearance), and bed load (larger particles moving along the bottom).
• Flow types include laminar (straight lines) in slower streams and turbulent (swirling motion) in faster streams.
• Erosion and sediment transport are affected by water velocity and particle shape, with denser grains settling more rapidly.

Groundwater Systems

• Artesian systems occur when groundwater rises above its original level due to confined aquifers and pressure from surrounding aquitards.
• Flowing artesian wells arise when pressure is greater than ground level; non-flowing artesian wells occur below ground level.

Glacial Features

• Glaciers are thick ice masses formed by accumulated snow; valley (alpine) glaciers flow down valleys, while ice sheets expand in all directions.
• Ice shelves are large, flat glacier extensions into oceans.
• Glaciers transport materials through plucking, a process where ice lifts rocks from the ground as it flows.

Explore the fascinating world of igneous rocks with this quiz, covering various types and their characteristics. Delve into textures, formation processes, and key concepts like Bowen's Reaction Series and magmatic differentiation.