Igneous Rocks and Textures

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What determines the dark color of obsidian?

Crystallization process

Presence of metallic ions (correct)

High silica content

Gas escape from molten rocks

Which rock is the intrusive equivalent of basalt?

Diorite

Gabbro (correct)

Pumice

Andesite

What is the composition of andesite primarily characterized by?

Presence of only dark silicates

High quartz content

Light-colored minerals only

Medium-gray, fine-grained texture (correct)

What occurs during magmatic differentiation?

Certain minerals remove elements from the magma Signup and view all the answers

Which of the following describes crystal settling?

Denser minerals sink to the bottom of the magma chamber Signup and view all the answers

What are phenocrysts primarily associated with?

Fine-grained volcanic rocks Signup and view all the answers

What role does Bowen's Reaction Series play in igneous rocks?

Illustrates the mineral crystallization sequence during cooling Signup and view all the answers

What texture does pumice exhibit after gas escape from molten rocks?

Grey, frothy mass Signup and view all the answers

What characterizes fine-grained igneous rock?

Crystals that can only be distinguished by a polarizing microscope Signup and view all the answers

Which term refers to sedimentary rocks formed from the consolidation of weathered rock fragments?

Detrital sedimentary rocks Signup and view all the answers

How are coarse-grained igneous rocks formed?

From large magma masses cooling slowly at depth Signup and view all the answers

What are Phenocrysts in porphyritic igneous rocks?

Large crystals surrounded by a matrix of smaller crystals Signup and view all the answers

What does the term 'sedimentary' indicate about the nature of these rocks?

They form from solid material that settled from fluid Signup and view all the answers

Which of the following is an example of a chemical sedimentary rock formation process?

Precipitation of ions from water Signup and view all the answers

In detrital sedimentary rocks, how are they classified?

By the size of the particles they contain Signup and view all the answers

What is the most common product of chemical weathering of silicate minerals in detrital sedimentary rocks?

Clay minerals and Quartz Signup and view all the answers

What is the dissolved load in a stream primarily influenced by?

Groundwater contributions Signup and view all the answers

Which characteristic of suspended load affects how long sediment stays suspended in a stream?

Settling velocity of particles Signup and view all the answers

What is the process where concentric slabs of rock begin to break loose due to reduced pressure from erosion?

Sheeting Signup and view all the answers

What effect does increasing water velocity have on sediment transport in turbulent flow?

Increases the ability to erode and transport sediment Signup and view all the answers

Which type of soil structure tends to have slower water infiltration?

Spheroidal Signup and view all the answers

What primarily influences soil fertility?

Amount of organic matter Signup and view all the answers

How do flat grains behave compared to spherical grains in a stream?

They remain suspended longer than spherical grains Signup and view all the answers

What is the term used to describe the activity of organisms affecting soil?

Bioturbation Signup and view all the answers

What type of flow is characterized by a straight-line path and is common in slow-moving streams?

Laminar Flow Signup and view all the answers

What does the bed load consist of in a stream?

Material too large to be carried in suspension Signup and view all the answers

Which of the following is NOT a control of soil formation?

Soil color Signup and view all the answers

Residual soils are primarily formed from which of the following?

Bedrock parent material Signup and view all the answers

Which of the following accurately describes how particles move in bed load transport?

By rolling and sliding along the bottom Signup and view all the answers

What is the significance of slope orientation in soil formation?

Influences temperature and moisture levels Signup and view all the answers

What is meant by 'capacity' in relation to streamflow?

The maximum load transported per unit of time Signup and view all the answers

How does precipitation affect soil?

It determines leaching degree and soil fertility. Signup and view all the answers

What happens to the water table around a well when substantial amounts of water are withdrawn?

It lowers, resulting in a Cone of Depression. Signup and view all the answers

In which situation does an artesian well occur?

Water is confined to an aquifer inclined with one end exposed. Signup and view all the answers

What characterizes a nonflowing artesian well?

The pressure surface is at ground level or below. Signup and view all the answers

What are piedmont glaciers?

Glaciers that occupy lowlands at the base of steep mountains. Signup and view all the answers

How do outlet glaciers function?

They flow down slopes, extending from valley glaciers. Signup and view all the answers

What is the main role of aquitards in artesian systems?

They prevent water from escaping through overlying layers. Signup and view all the answers

What type of glacier is formed when valley glaciers emerge from confining walls?

Piedmont Glacier Signup and view all the answers

What is the characteristic of a flowing artesian well?

It is drilled directly into a confined aquifer with high pressure above ground. Signup and view all the answers

Study Notes

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.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

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.