Minerals in Igneous Rocks

Minerals in Rocks

• Feldspar and quartz are the most prevalent minerals in various rock types.
• Pyroxene consists of calcium, aluminium, magnesium, iron, and silica, commonly found in meteorites.
• Amphibole is composed of aluminium, calcium, silica, iron, magnesium; significant in the asbestos industry.
• Mica includes potassium, aluminium, magnesium, iron, and silica; commonly featured in igneous and metamorphic rocks.
• Olivine is rich in magnesium, iron, and silica, often used in jewellery, commonly occurs in basaltic rocks.

Rock Classification

• Felsic rocks are characterized by high silica content (65-70%) and are typically lighter in color; associated with explosive volcanic activity.
• Mafic rocks contain greater amounts of magnesium and iron, resulting in darker, denser appearances.
• Ultramafic rocks are specifically dominated by magnesium and iron.
• Sedimentary rocks form from the compaction of sediments, arising from the deposition of rock fragments.

Types of Sedimentary Rocks

• Mechanically formed sedimentary rocks include sandstone, conglomerate, shale, and loess.
• Lithification is the process transforming sediments into sedimentary rocks through compaction.

Metamorphic Processes

• Dynamic metamorphism involves mechanical disruption and the reorganization of minerals without significant chemical changes.
• Thermal metamorphism results in chemical alteration and recrystallization due to heat.
• Contact metamorphism occurs when rocks are influenced by nearby hot magma.
• Regional metamorphism is induced by tectonic forces, elevated pressure, and temperature.

Metamorphic Rock Structure

• Foliation is the arrangement of minerals in layers or lines within metamorphic rocks.
• Banding occurs when minerals are organized into alternating light and dark layers.

Magma and Lava

• Lava refers to magma that has reached the Earth's surface.
• Eruptions may release lava flows, pyroclastic materials, volcanic bombs, ash, and various gases.
• Silica content in magma influences viscosity, temperature, and explosive potential.

Lava Types

• Felsic lava has high silica content (65-70%) and is explosive.
• Intermediate lava contains 52-63% silica and is less viscous.
• Mafic magma ranges from 45-52% silica and is generally fluid and non-explosive.

Temperature Influences

• Latitude impacts temperature directly, with higher latitudes receiving less insolation.
• Altitude also affects temperature; as altitude increases, temperature typically decreases.
• Surface and distance from the sea can moderate temperatures due to maritime influence.

Temperature Inversions

• Surface temperature inversion is when cool air is trapped under a layer of warmer air at the surface.
• Conditions such as clear skies and still air promote temperature inversions, affecting local weather patterns.
• Urban Heat Island (UHI) effect results from human activities, causing elevated temperatures in urban areas.

Consequences of Temperature Inversion

• Formation of fog occurs when warm air rests above cold air, cooling it and causing condensation.
• Frost impacts arise from warm air condensing at freezing temperatures, potentially damaging crops.

Atmospheric Pressure and Wind

• Atmospheric pressure is defined as the weight of air per unit area, decreasing with height.
• Wind is driven from high-pressure areas to low-pressure areas; tightly spaced isobars indicate strong winds.
• The pressure gradient force influences wind velocity and direction, while friction can slow wind speed.

Explore the essential minerals found in igneous rocks, including feldspar, quartz, and pyroxene. This quiz covers the classification of rocks based on their chemical composition and the formation of extrusive igneous rocks like basalt and andesite. Test your knowledge of these geological concepts!