Questions and Answers
What is the difference between magma and lava?
What is the freezing temperature range for magma?
1100C - 650C, depending on composition.
What is the difference between lava and pyroclastics?
Lava is melted rock formed on the surface, while pyroclastics are cooled rock fragments.
What is the difference between volcanic and plutonic rocks?
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How does the cooling rate vary for intrusive and extrusive melts?
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Where does partial melting occur in the Earth?
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What three mechanisms cause melting?
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Explain how decompression melting works and provide an example of where it occurs.
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Explain how flux melting works and give an example of an environment where it occurs.
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Explain how heat transfer melting works and where it typically occurs.
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What are the dominant components of magma?
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How does dry magma differ from wet magma?
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How does felsic magma differ from mafic magma?
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Explain the process of assimilation as it relates to magma.
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What are two reasons that magma rises?
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What parameters govern low viscosity magma?
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Explain fractional crystallization and how Bowen's Reaction Series predicts this process.
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What are sills and dikes?
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What is a pluton? Batholith? Laccolith? Name an example of a batholith in California.
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Define aphanitic.
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Define phaneritic.
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Define porphyritic.
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What is pumice?
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What is scoria?
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What is tuff?
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What is the correlation between volcanic activity and plate tectonic activities?
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Which type of plate boundary does not typically have volcanic activity?
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What four geologic settings does igneous activity occur?
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Name an example of a large igneous province in North America.
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What is the difference between sediment and sedimentary rock?
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What is 'basement' rock?
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What are the four classes of sedimentary rock and a brief description of each?
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How does siliceous differ from argillaceous composition?
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Describe the 5-step process for creating detrital (clastic) sedimentary rocks.
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What are the two common cements for detrital rocks?
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What is the correlation between transport distance and grain size?
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What is the correlation between transport distance and roundness/sphericity?
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What is the correlation between transport distance and sorting?
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What is an example of a sedimentary environment that produces breccia?
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What is an example of a sedimentary environment that produces shale/mudstone?
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What is an example of a sedimentary environment that produces sandstone?
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What is an example of a sedimentary environment that produces fossil limestone?
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What is an example of a sedimentary environment that produces rock salt?
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What is the most common mineral in sandstone?
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How does arkose differ from quartz sandstone?
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What is the definition of sand (size range)?
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What sedimentary environment produces oil and gas?
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What is chert?
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What is flint?
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What is jasper?
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What is petrified wood?
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What is agate?
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Where is travertine found? What is its composition?
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Name two examples of evaporites.
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What is the term for the boundary between two sedimentary beds?
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Why does bedding form?
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What is bioturbation and how does it alter bedding?
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What type of map shows rock formations?
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What process creates cross bedding in sand dunes?
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Describe the grading in a turbidite deposit and name a depositional environment where these form.
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What defines a glacial environment?
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What defines a streams environment?
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What defines alluvial fans?
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What defines dunes?
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What defines lakes as a sedimentary environment?
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What defines beaches?
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What defines shallow marine environments?
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What defines deep ocean environments?
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In general, where do basins form on Earth?
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What happens to the position of the shoreline during a transgressive sea level change?
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What happens to the position of the shoreline during a regressive sea level change?
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What is diagenesis and what is its temperature range?
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What is a protolith?
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What defines a metamorphic texture?
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What is an example of a polymorph of andalusite?
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Describe the process of metamorphic pressure solution.
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What are the four agents of metamorphism?
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What are the sources of heat in the Earth for metamorphism?
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What is the pressure range (in kbars) for metamorphism?
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What is differential stress? What are the two types?
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In metamorphic rocks, preferred mineral orientation can develop via pressure solution or plastic deformation. What is the difference?
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What is metasomatism?
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What is the general distinction between foliated and non-foliated metamorphic rocks?
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Define slate.
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Define phyllite.
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Define schist.
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Define gneiss.
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Define metaconglomerate.
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What is a porphyroblast?
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Describe a migmatite.
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Define quartzite.
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Define marble.
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Define serpentine.
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Define amphibolite.
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What is a 'shield' as it relates to plate tectonics?
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What is the California State Rock? Where do you find it in California?
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What are metamorphic environments?
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What are the 3 categories of products of volcanic eruptions?
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What four factors does magma viscosity depend on?
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What are the characteristics of mafic lava flows?
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What is the difference between pahoehoe and aa?
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Study Notes
Magma and Lava
- Magma is molten rock found beneath the Earth's surface, while lava is magma that has reached the surface.
Freezing Temperatures
- Magma freezes in a temperature range of 1100°C to 650°C, influenced by its chemical composition.
Lava vs. Pyroclastics
- Lava forms on the surface as molten rock, creating streams or mounds, whereas pyroclastics are fragments that have cooled and solidified.
Volcanic vs. Plutonic Rocks
- Volcanic rocks are formed from lava solidifying quickly on the surface; plutonic rocks solidify from magma deep within the Earth.
Cooling Rates
- Extrusive melts cool rapidly, preventing large crystal formation; intrusive melts cool slowly, allowing for crystal growth.
Partial Melting Locations
- Occurs in the Earth's crust and upper mantle, where temperature and pressure conditions are conducive.
Melting Mechanisms
- Melting in the Earth is caused by pressure release, addition of volatiles, and heat transfer.
Decompression Melting
- This process occurs when high pressure stops mantle rock from melting; lowering the pressure allows for melting, found in mantle plumes and mid-ocean ridges.
Flux Melting
- Occurs with the addition of volatiles like H2O and CO2, lowering melting temperatures; commonly seen in subduction zones.
Heat Transfer Melting
- Happens when rising magma heats surrounding crustal rocks, causing them to melt, prevalent in high volcanic activity areas.
Components of Magma
- Magma consists of solids (minerals), liquids (mobile ions like Si and O), and gases (dissolved volatiles).
Wet vs. Dry Magma
- Dry magma contains few volatiles; wet magma can have up to 15% volatiles, influencing its properties.
Felsic vs. Mafic Magma
- Felsic magma has a higher silica content (66-76%); mafic magma has lower silica content (45-52%).
Assimilation Process
- This occurs when magma melts surrounding rock, incorporating fragments (xenoliths) and altering its composition.
Magma Rising
- Magma rises due to being less dense than surrounding rocks and the buoyancy effect, along with pressure from overlying rock.
Viscosity Influences
- Low viscosity magma is characterized by high temperature, low silica, and high volatiles.
Fractional Crystallization
- Settling of early-formed crystals alters magma composition; Bowen's Reaction Series describes this process.
Sills and Dikes
- Sills are parallel to rock layers; dikes cut across them, causing expansion and thermal alteration of the invaded rock.
Types of Intrusive Bodies
- A pluton is a large volume of intrusive rock; batholiths are massive plutons, such as the Sierra Nevadas in California. Laccoliths are mushroom-shaped intrusions.
Rock Textures
- Aphanitic rocks are fine-grained and extrusive; phaneritic rocks are coarse-grained and intrusive; porphyritic rocks have a mix of crystal sizes.
Specific Rock Types
- Pumice is frothy and floats; scoria is a glassy mafic rock; tuff is volcanic ash deposited on land.
Volcanic Activity and Tectonics
- Most volcanic activity occurs at subduction zones; transform boundaries exhibit little volcanic activity.
Settings for Igneous Activity
- Occurs in volcanic arcs, hot spots, continental rifts, and mid-ocean ridges.
Sedimentary Rock Transition
- Soft sediment transforms into cemented sedimentary rock with increasing burial depth.
Sedimentary Rock Classes
- Clastic, biochemical, organic, and chemical are the four classes, defined by their composition and formation processes.
Sedimentary Composition
- Siliceous rocks are quartz-rich; argillaceous rocks are clay-rich.
Detrital Sedimentary Rock Formation
- Formed through weathering, erosion, transportation, deposition, and lithification.
Common Cementing Processes
- Compaction and cementation are typical for detrital rocks, solidifying sediment into rock.
Grain Size and Transport Distance
- Increased transport distance correlates with smaller grain size, increased roundness, and better sorting.
Breccia Environment
- Typically found in environments like talus under cliffs.
Shale/Mudstone Environment
- Common in quiet water settings such as floodplains and deltas.
Sandstone Environment
- Commonly found in beach and dune settings.
Fossil Limestone Environment
- Typically forms in warm, shallow, clear marine waters rich in oxygen.
Rock Salt Environment
- Formed from the evaporation of sea or lake water.
Sand Composition
- Defined as grain sizes from 1/16 mm to 2 mm, primarily quartz in sandstone.
Oil and Gas Environment
- Found in sedimentary basins.
Chert and Varieties
- Nonbiogenic with many varieties; flint is colored by organic matter, while jasper contains iron oxides coloring it red or yellow.
Travertine Locations
- Found in thermal hot springs and caves, primarily composed of calcium carbonate (CaCO3).
Evaporite Examples
- Halite (rock salt) and gypsum are common evaporites.
Bedding Plane Definition
- The boundary between two sedimentary beds, formed due to changes in deposition conditions.
Bioturbation Effect
- Disrupts bedding layers due to burrowing organisms.
Geologic Maps
- Show rock formations across a geographic area.
Cross Bedding Formation
- Created by the migration of ripples and dunes.
Turbidite Grading
- Coarse material settles first, followed by finer particles in deep ocean environments.
Various Terrestrial Environments
- Glacial, streams, alluvial fans, dunes, and lakes characterize environments shaped by their respective sediment transport methods.
Marine Environments
- Beaches, shallow marine, and deep ocean environments are defined by sediment types and deposition processes.
Basin Formation
- Occur where tectonic activity creates depressions in the Earth's crust.
Transgressive vs. Regresive Shoreline Changes
- Transgression shifts sediment belts landward; regression shifts them seaward.
Diagenesis Process
- Refers to physical, chemical, and biological changes occurring in sediments prior to metamorphism, generally at temperatures below 300°C.
Protolith Definition
- The original rock type undergoing metamorphosis.
Metamorphic Texture Characteristics
- Defined by the alignment of platy minerals and light/dark banding.
Polymorph Example
- Kyanite is a polymorph of andalusite.
Metamorphic Pressure Solution
- Occurs when mineral grains dissolve at contact points under pressure.
Agents of Metamorphism
- Heat, pressure, compression, shear, and hot water contribute to metamorphic change.
Heat Sources for Metamorphism
- The geothermal gradient, magmatic intrusions, and pressure from overlying layers.
Pressure Range for Metamorphism
- Typically between 2 to 12 kbars.
Differential Stress
- Stress applied unevenly in one direction, including normal stress (perpendicular) and shear stress (sideways movement).
Pressure Solution vs. Plastic Deformation
- Pressure solution occurs at lower temperatures in wet rocks; plastic deformation happens at higher temperatures.
Hydrothermal Alteration
- Known as metasomatism, involves mineral changes due to hot water interaction.
Distinction of Metamorphic Rocks
- Foliated rocks exhibit layered textures; non-foliated rocks lack planar fabrics.
Metamorphic Rock Examples
- Slate (from mudstone), phyllite (from shale), schist (from various parent rocks), and gneiss (shows banding).
Porphyroblast Definition
- Large, non-mica mineral crystals formed during metamorphism.
Migmatite Description
- Represents a partially melted state of gneiss.
Quartzite Composition
- Almost pure quartz derived from sandstone.
Marble Composition
- Coarse crystalline rock from limestone.
Serpentine Protolith
- Originates from basalt, gabbro, or ultramafic igneous rock.
Amphibolite Characteristics
- Dominated by dark amphibole minerals, derived from basalt or gabbro.
"Shield" in Plate Tectonics
- Refers to extensive areas of ancient high-grade metamorphic rock.
California State Rock
- Serpentine, found throughout various regions of California.
Metamorphic Environments
- Include thermal, burial, dynamic, regional, hydrothermal, subduction, and shock environments.
Products of Volcanic Eruptions
- Include lava flows, pyroclastic debris, and volcanic gases.
Factors of Magma Viscosity
- Composition (primarily silica), temperature, gas content, and crystal content.
Characteristics of Mafic Lava Flows
- Very hot with low silica and low viscosity.
Pahoehoe vs. Aa
- Pahoehoe is smooth and ropy; aa is jagged and rough, both referring to different basalt textures.
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Explore key differences between magma and lava in this quiz. Understand the conditions that define their characteristics and learn about the freezing temperatures of magma. This resource is perfect for geology students looking to solidify their knowledge on volcanic materials.