Geology Concepts: Magma and Lava

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Questions and Answers

What is the difference between magma and lava?

Magma is only found in volcanoes

Magma is below ground and lava is above ground (correct)

Magma is liquid and lava is solid

Both magma and lava are the same

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?

Volcanic rocks are formed near or at the surface, while plutonic rocks solidify deep within the Earth. Signup and view all the answers

How does the cooling rate vary for intrusive and extrusive melts?

Extrusive melts cool rapidly while intrusive melts cool slowly. Signup and view all the answers

Where does partial melting occur in the Earth?

In the crust and upper mantle. Signup and view all the answers

What three mechanisms cause melting?

Pressure release, volatile addition, and heat transfer. Signup and view all the answers

Explain how decompression melting works and provide an example of where it occurs.

Decompression melting occurs when pressure decreases, allowing hot mantle rock to melt. An example is mantle plumes. Signup and view all the answers

Explain how flux melting works and give an example of an environment where it occurs.

Flux melting occurs through the addition of volatiles that lower the melting temperature of rocks, commonly seen in subduction zones. Signup and view all the answers

Explain how heat transfer melting works and where it typically occurs.

Heat transfer melting happens when rising magma raises the temperature of the surrounding crust, usually found in high volcanic activity areas. Signup and view all the answers

What are the dominant components of magma?

Solid mineral crystals, liquid melt, and variable amounts of dissolved gas. Signup and view all the answers

How does dry magma differ from wet magma?

Dry magma has scarce volatiles while wet magma can contain up to 15% of volatiles. Signup and view all the answers

How does felsic magma differ from mafic magma?

Felsic magma has 66 - 76% silica, while mafic magma has 45 - 52% silica. Signup and view all the answers

Explain the process of assimilation as it relates to magma.

Assimilation occurs when magma melts surrounding wall rock, altering its composition. Signup and view all the answers

What are two reasons that magma rises?

It is less dense and more buoyant than surrounding rocks. Signup and view all the answers

What parameters govern low viscosity magma?

Higher temperature, lower silica content, and higher volatile content. Signup and view all the answers

Explain fractional crystallization and how Bowen's Reaction Series predicts this process.

Fractional crystallization involves the settling of early-formed crystals which remove certain elements from the liquid magma. Signup and view all the answers

What are sills and dikes?

Sills are parallel to rock layering, while dikes cut across preexisting layers. Signup and view all the answers

What is a pluton? Batholith? Laccolith? Name an example of a batholith in California.

A pluton is a large volume of intrusive rock; a batholith is a massive pluton. An example in California is the Sierra Nevadas. Signup and view all the answers

Define aphanitic.

Fine grained, rapid cooling, and crystals do not have time to grow. Signup and view all the answers

Define phaneritic.

Coarse grained, slow cooling, crystals have time to grow. Signup and view all the answers

Define porphyritic.

A mixture of coarse and fine crystals, indicating a two-stage cooling history. Signup and view all the answers

What is pumice?

A frothy felsic rock full of vesicles. Signup and view all the answers

What is scoria?

A glassy, vesicular mafic rock. Signup and view all the answers

What is tuff?

Volcanic ash that has fallen on land. Signup and view all the answers

What is the correlation between volcanic activity and plate tectonic activities?

Volcanic activities occur at subduction zones. Signup and view all the answers

Which type of plate boundary does not typically have volcanic activity?

Transform boundaries. Signup and view all the answers

What four geologic settings does igneous activity occur?

Volcanic arcs, isolated hot spots, continental rifts, mid-ocean ridges. Signup and view all the answers

Name an example of a large igneous province in North America.

Columbia River of Flood Basalts. Signup and view all the answers

What is the difference between sediment and sedimentary rock?

Sediment is loose material, while sedimentary rock is cemented sediment. Signup and view all the answers

What is 'basement' rock?

Rocks below sedimentary cover. Signup and view all the answers

What are the four classes of sedimentary rock and a brief description of each?

<ol> <li>Clastic - loose rock fragments cemented together. 2. Biochemical - cemented shells of organisms. 3. Organic - carbon-rich remains of organisms. 4. Chemical - minerals crystallized from water.</li> </ol> Signup and view all the answers

How does siliceous differ from argillaceous composition?

Siliceous is quartz-rich, whereas argillaceous is clay-rich. Signup and view all the answers

Describe the 5-step process for creating detrital (clastic) sedimentary rocks.

<ol> <li>Weathering - rock disintegration. 2. Erosion - removal of sediments. 3. Transportation - dispersal. 4. Deposition - settling. 5. Lithification - solidification.</li> </ol> Signup and view all the answers

What are the two common cements for detrital rocks?

Compaction and cementation. Signup and view all the answers

What is the correlation between transport distance and grain size?

As transport distance increases, grain size decreases. Signup and view all the answers

What is the correlation between transport distance and roundness/sphericity?

As transport distance increases, roundness/sphericity increases. Signup and view all the answers

What is the correlation between transport distance and sorting?

Degree of sorting increases with transport distance. Signup and view all the answers

What is an example of a sedimentary environment that produces breccia?

Talus under a cliff face. Signup and view all the answers

What is an example of a sedimentary environment that produces shale/mudstone?

Quiet water depositional environments like floodplains or lagoons. Signup and view all the answers

What is an example of a sedimentary environment that produces sandstone?

Common in beach and dune settings. Signup and view all the answers

What is an example of a sedimentary environment that produces fossil limestone?

Warm, tropical, shallow, clear marine water. Signup and view all the answers

What is an example of a sedimentary environment that produces rock salt?

Sea or lake water. Signup and view all the answers

What is the most common mineral in sandstone?

Quartz. Signup and view all the answers

How does arkose differ from quartz sandstone?

Arkose has abundant feldspar, while sandstone is made of sand-sized particles typically rich in quartz. Signup and view all the answers

What is the definition of sand (size range)?

1/16 mm - 2 mm. Signup and view all the answers

What sedimentary environment produces oil and gas?

Sedimentary basins. Signup and view all the answers

What is chert?

Nonbiogenic with many varieties. Signup and view all the answers

What is flint?

Colored black or gray from organic matter. Signup and view all the answers

What is jasper?

Bright red or yellow from Fe-oxides. Signup and view all the answers

What is petrified wood?

Wood grain preserved by silica. Signup and view all the answers

What is agate?

Concentrically layered rings. Signup and view all the answers

Where is travertine found? What is its composition?

Found in thermal hot springs and caves; its composition is CaCO3. Signup and view all the answers

Name two examples of evaporites.

Halite (rock salt) and gypsum. Signup and view all the answers

What is the term for the boundary between two sedimentary beds?

Bedding plane. Signup and view all the answers

Why does bedding form?

Bedding reflects changing conditions during deposition. Signup and view all the answers

What is bioturbation and how does it alter bedding?

Bioturbation is the disturbance of sediment layers by burrowing creatures. Signup and view all the answers

What type of map shows rock formations?

Geologic maps. Signup and view all the answers

What process creates cross bedding in sand dunes?

Created by ripple and dune migration. Signup and view all the answers

Describe the grading in a turbidite deposit and name a depositional environment where these form.

Coarsest material settles first, followed by medium and finer materials; they occur in the deep ocean. Signup and view all the answers

What defines a glacial environment?

A terrestrial environment due to the movement of ice. Signup and view all the answers

What defines a streams environment?

A terrestrial environment due to water carrying large clasts during floods. Signup and view all the answers

What defines alluvial fans?

Sediments pile up at a mountain front due to the deposition from flowing water. Signup and view all the answers

What defines dunes?

Terrestrial environments due to sand-dune structures created by wind. Signup and view all the answers

What defines lakes as a sedimentary environment?

Terrestrial environment characterized by large ponded bodies of water. Signup and view all the answers

What defines beaches?

Marine environment due to sand moved along the coastline. Signup and view all the answers

What defines shallow marine environments?

Marine environments characterized by finer sands and silts. Signup and view all the answers

What defines deep ocean environments?

Marine environments where fines settle out far from land. Signup and view all the answers

In general, where do basins form on Earth?

Basins form where tectonic activity creates space. Signup and view all the answers

What happens to the position of the shoreline during a transgressive sea level change?

Sediment belts shift landward. Signup and view all the answers

What happens to the position of the shoreline during a regressive sea level change?

Depositional belts shift seaward. Signup and view all the answers

What is diagenesis and what is its temperature range?

Physical, chemical, and biological changes to sediment between burial and metamorphism (~300C). Signup and view all the answers

What is a protolith?

Preexisting rocks. Signup and view all the answers

What defines a metamorphic texture?

Alignment of platy minerals and creation of alternating light/dark bands. Signup and view all the answers

What is an example of a polymorph of andalusite?

Kyanite. Signup and view all the answers

Describe the process of metamorphic pressure solution.

Mineral grains partially dissolve where their surfaces press together. Signup and view all the answers

What are the four agents of metamorphism?

Heat, pressure, compression and shear, and hot water. Signup and view all the answers

What are the sources of heat in the Earth for metamorphism?

The geothermal gradient, magmatic intrusions, and compression. Signup and view all the answers

What is the pressure range (in kbars) for metamorphism?

2 - 12 kbar range. Signup and view all the answers

What is differential stress? What are the two types?

Differential stress is stress greater in one orientation; types are normal stress and shear stress. Signup and view all the answers

In metamorphic rocks, preferred mineral orientation can develop via pressure solution or plastic deformation. What is the difference?

Pressure solution occurs in wet rocks at low temperatures, while plastic deformation occurs at higher temperatures. Signup and view all the answers

What is metasomatism?

Hydrothermal alteration. Signup and view all the answers

What is the general distinction between foliated and non-foliated metamorphic rocks?

Foliated rocks display parallel layers, while non-foliated rocks lack a planar fabric. Signup and view all the answers

Define slate.

Fine-grained, low-grade metamorphic shale. Signup and view all the answers

Define phyllite.

Fine-grained, mica-rich rock. Signup and view all the answers

Define schist.

Fine to coarse rock with larger micas. Signup and view all the answers

Define gneiss.

Distinct compositional bands, often contoured. Signup and view all the answers

Define metaconglomerate.

A metamorphosed conglomerate. Signup and view all the answers

What is a porphyroblast?

Large non-mica minerals. Signup and view all the answers

Describe a migmatite.

Partially melted gneiss. Signup and view all the answers

Define quartzite.

Almost pure quartz in composition. Signup and view all the answers

Define marble.

Coarsely crystalline calcite or dolomite. Signup and view all the answers

Define serpentine.

Protolith: basalt, gabbro, or ultramafic igneous rock. Signup and view all the answers

Define amphibolite.

Dominated by dark amphibole minerals. Signup and view all the answers

What is a 'shield' as it relates to plate tectonics?

Large regions of ancient high-grade rocks. Signup and view all the answers

What is the California State Rock? Where do you find it in California?

Serpentine; it's found in various locations such as the Sierra Nevada. Signup and view all the answers

What are metamorphic environments?

Various environments defined by their conditions, including thermal, burial, dynamic, and hydrothermal alterations. Signup and view all the answers

What are the 3 categories of products of volcanic eruptions?

Lava flows, pyroclastic debris, and volcanic gases. Signup and view all the answers

What four factors does magma viscosity depend on?

Composition, temperature, gas content, and crystal content. Signup and view all the answers

What are the characteristics of mafic lava flows?

Very hot, low silica, and low viscosity. Signup and view all the answers

What is the difference between pahoehoe and aa?

Pahoehoe describes basalt with a glassy, ropy texture; aa describes jagged, angular basalt. Signup and view all the answers

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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Description

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.