The document describes calculating the viscosity of a hydrous, leucogranitic melt using a regression model. It provides background on estimating magma viscosity and factors that influence it like temperature, water content, and crystal content. It then presents the problem of calculating the viscosity of a rhyolite magma at 900°C with 2% water and 0.03% crystal content. A plan is outlined to implement a VFT model to calculate melt viscosity and incorporate crystal content using an equation to find the final magma viscosity. A spreadsheet is presented carrying out these calculations.
This document summarizes the key characteristics and types of magma. It defines magma as a mixture of molten or semi-molten rock found beneath the Earth's surface. Magma forms through mechanisms like decompression melting when hot mantle material rises and melts lower pressure rock, or flux melting when water or carbon dioxide lowers the melting temperature of mantle rock. Magma can be classified based on its chemical composition into basaltic, andesitic, or rhyolitic types depending on silicon and iron/magnesium content, and each type has distinct physical properties like temperature, viscosity, and gas content that determine explosiveness. Magma is also differentiated based on how it formed, such as primitive, primary, parental
Mantle melting occurs when heat and pressure cause partial melting of the mantle, producing basaltic magma. Basalt is the most common volcanic rock on Earth and can be further differentiated to form other igneous rock types. Evidence for the composition and processes of the mantle comes from ophiolites, dredged samples from ocean floors, nodules contained in basalts, and xenoliths brought up from deep in the mantle via kimberlite eruptions. Together this evidence indicates that the upper mantle is composed predominantly of the minerals olivine, orthopyroxene, and clinopyroxene which make up the rocks dunite, harzburgite, and lherzol
This document discusses metamorphism and metamorphic rocks. Metamorphic rocks form from existing igneous, sedimentary, or other metamorphic rocks through heat, pressure, and chemically reactive fluids. Metamorphism progresses incrementally and involves the growth of new minerals and deformation of existing ones. Metamorphism occurs in various settings like contact, regional, and burial metamorphism. Factors like heat, pressure, and fluids drive changes in mineralogy and texture. Metamorphic grade is indicated by index minerals and results in foliated and non-foliated rock types.
This document discusses metamorphism and metamorphic rocks. It defines metamorphism as a change in shape of pre-existing rocks due to heat and pressure below the surface. It describes different types of metamorphism including contact, dynamic, and regional metamorphism. It also defines foliated and non-foliated metamorphic rocks, providing examples like slate, schist, and gneiss. The document aims to explain metamorphic concepts and rock types to students.
The document discusses the textures of sedimentary rocks. It defines texture as the shape, size, and arrangement of particles that make up sediments and sedimentary rocks. There are three main aspects of texture discussed: grain size, particle shape, and fabrics. Grain size is measured using various scales and distributions are analyzed mathematically. Particle shape is defined by form, roundness, and surface texture. Fabrics consider grain orientation, packing, and relations which influence porosity. Texture provides insight into the depositional environment and post-depositional changes sediments undergo.
This document provides an overview of volcanoes. It begins by defining a volcano as a vent in the Earth's surface through which molten rock and gases erupt. It then discusses the internal structure of volcanoes including magma, which is molten rock below the surface. The causes of volcanism are explained in relation to plate tectonics. Different types of volcanoes are classified based on factors like eruption intensity, magma composition, and shape. Volcanic landforms that form from intrusive and extrusive volcanic activity are also outlined. In summary, the document covers the key components and processes involved in volcanism.
Bowen’s Reaction Series
ROCKS:
There are three kinds of rocks, that are defined on the basis of how they formed.
Igneous Rocks:
are formed from the solidification of molten rock or magma.
Sedimentary Rocks:
form through when materials at the earth's surface (sediments) are buried and hardened (lithified).
Metamorphic Rocks:
are formed when older rocks are changed by heat and pressure without being melted.
This document discusses mechanisms of magma diversification, including partial melting, crystal fractionation, thermogravitational diffusion, liquid immiscibility, vapor transport, magma mixing, and assimilation. Partial melting refers to processes where a magmatic melt is created from a portion of solid rock. Crystal fractionation involves the separation of crystals from melt through settling, filtering, or flow. Thermogravitational diffusion causes components to separate due to temperature and density gradients. Liquid immiscibility can cause magma to split into immiscible liquid fractions. Vapor transport involves volatile release upon pressure reduction. Magma mixing combines magmas of different compositions. Assimilation incorporates country rock into magma through reaction.
This document summarizes the key characteristics and types of magma. It defines magma as a mixture of molten or semi-molten rock found beneath the Earth's surface. Magma forms through mechanisms like decompression melting when hot mantle material rises and melts lower pressure rock, or flux melting when water or carbon dioxide lowers the melting temperature of mantle rock. Magma can be classified based on its chemical composition into basaltic, andesitic, or rhyolitic types depending on silicon and iron/magnesium content, and each type has distinct physical properties like temperature, viscosity, and gas content that determine explosiveness. Magma is also differentiated based on how it formed, such as primitive, primary, parental
Mantle melting occurs when heat and pressure cause partial melting of the mantle, producing basaltic magma. Basalt is the most common volcanic rock on Earth and can be further differentiated to form other igneous rock types. Evidence for the composition and processes of the mantle comes from ophiolites, dredged samples from ocean floors, nodules contained in basalts, and xenoliths brought up from deep in the mantle via kimberlite eruptions. Together this evidence indicates that the upper mantle is composed predominantly of the minerals olivine, orthopyroxene, and clinopyroxene which make up the rocks dunite, harzburgite, and lherzol
This document discusses metamorphism and metamorphic rocks. Metamorphic rocks form from existing igneous, sedimentary, or other metamorphic rocks through heat, pressure, and chemically reactive fluids. Metamorphism progresses incrementally and involves the growth of new minerals and deformation of existing ones. Metamorphism occurs in various settings like contact, regional, and burial metamorphism. Factors like heat, pressure, and fluids drive changes in mineralogy and texture. Metamorphic grade is indicated by index minerals and results in foliated and non-foliated rock types.
This document discusses metamorphism and metamorphic rocks. It defines metamorphism as a change in shape of pre-existing rocks due to heat and pressure below the surface. It describes different types of metamorphism including contact, dynamic, and regional metamorphism. It also defines foliated and non-foliated metamorphic rocks, providing examples like slate, schist, and gneiss. The document aims to explain metamorphic concepts and rock types to students.
The document discusses the textures of sedimentary rocks. It defines texture as the shape, size, and arrangement of particles that make up sediments and sedimentary rocks. There are three main aspects of texture discussed: grain size, particle shape, and fabrics. Grain size is measured using various scales and distributions are analyzed mathematically. Particle shape is defined by form, roundness, and surface texture. Fabrics consider grain orientation, packing, and relations which influence porosity. Texture provides insight into the depositional environment and post-depositional changes sediments undergo.
This document provides an overview of volcanoes. It begins by defining a volcano as a vent in the Earth's surface through which molten rock and gases erupt. It then discusses the internal structure of volcanoes including magma, which is molten rock below the surface. The causes of volcanism are explained in relation to plate tectonics. Different types of volcanoes are classified based on factors like eruption intensity, magma composition, and shape. Volcanic landforms that form from intrusive and extrusive volcanic activity are also outlined. In summary, the document covers the key components and processes involved in volcanism.
Bowen’s Reaction Series
ROCKS:
There are three kinds of rocks, that are defined on the basis of how they formed.
Igneous Rocks:
are formed from the solidification of molten rock or magma.
Sedimentary Rocks:
form through when materials at the earth's surface (sediments) are buried and hardened (lithified).
Metamorphic Rocks:
are formed when older rocks are changed by heat and pressure without being melted.
This document discusses mechanisms of magma diversification, including partial melting, crystal fractionation, thermogravitational diffusion, liquid immiscibility, vapor transport, magma mixing, and assimilation. Partial melting refers to processes where a magmatic melt is created from a portion of solid rock. Crystal fractionation involves the separation of crystals from melt through settling, filtering, or flow. Thermogravitational diffusion causes components to separate due to temperature and density gradients. Liquid immiscibility can cause magma to split into immiscible liquid fractions. Vapor transport involves volatile release upon pressure reduction. Magma mixing combines magmas of different compositions. Assimilation incorporates country rock into magma through reaction.
The document provides an overview of mantle plumes and hotspots. It discusses that mantle plumes are columns of hot material rising from deep within the mantle, and hotspots are the surface expression of these plumes seen as volcanic regions. Hotspots have distinct geochemical signatures and are unrelated to tectonic plate boundaries. They can form hotspot tracks as the tectonic plate moves over them, leaving age-progressive volcanic chains. While hotspots were thought to be fixed in the mantle, evidence now suggests they may move slowly relative to each other over geologic timescales. Mantle plumes provide an explanation for various volcanic and tectonic phenomena seen in the interiors of tectonic plates.
Rock deformation is the process by which rocks change shape due to stress and heat. Structural geology studies rock deformation, which can occur through folds, faults, or joints. Folds involve the bending of sedimentary or volcanic rocks into undulating waves, commonly seen as anticlines and synclines or domes and basins. Faults are fractures where the earth's crust is displaced, and include dip-slip, strike-slip, and tensional or compressional faults. Joints are fractures without displacement and include columnar and sheeting joints.
This document discusses metamorphism and metamorphic rocks. It defines metamorphism as the change in rocks due to increases in temperature and pressure. There are different types of metamorphism including contact, regional, and cataclastic metamorphism. Regional metamorphism occurs over large areas and results in strongly foliated rocks like slates, schists and gneisses. The document describes the different grades of metamorphism from low to high and the typical minerals formed. It also discusses structures in metamorphic rocks like foliation and banding. In conclusion, different metamorphic rocks like slates, schists and gneisses have various economic uses as building materials.
This document summarizes the different grades of metamorphism: very low-grade, low-grade, medium-grade, and high-grade. Each grade is defined by the typical temperature and pressure conditions and indicator minerals present. Very low-grade occurs below 200°C and involves minerals like lawsonite. Low-grade occurs from 200-300°C and involves hydrous minerals. Medium-grade occurs from 400-550°C and involves minerals like staurolite and cordierite. High-grade occurs above 600°C and involves breakdown of minerals like muscovite. Isogrades are lines that indicate boundaries of metamorphic grade based on the appearance of indicator minerals.
- Magma forms by partial melting of the mantle or crust and consists of molten or semi-molten rock. It varies in temperature, pressure, density and composition depending on its origin and evolution.
- Magma evolves as it differentiates through fractional crystallization, assimilation, and mixing. Early crystallizing minerals remove elements from the magma, changing its composition over time according to Bowen's reaction series.
- Magma rises towards the Earth's surface where it cools and crystallizes to form either plutonic or volcanic rocks, depending on the cooling rate. Slow cooling results in large mineral crystals in plutonic rocks, while rapid cooling of lava forms volcanic rocks like obsidian with little
Introduction
Stratigraphy is the study of strata (sedimentary layers) in the Earth's crust, it is the relationship between rocks and time.
Stratigrapher are concerned with the observation, description and interpretation of direct and tangible evidence in rocks to determine the history of the Earth.
The combination of sedimentology and stratigraphy allows us to build up pictures of the Earth’s surface at different times in different places and relate them to each other through the relative ages of rocks
A more modern way of stating the same principle is that the laws of nature (laws of chemistry and physics) that have operated in the same way since the beginning of time.
And thus if we understand the physical and chemical principles by which nature operates, we can assume that nature operated the same way in the past.
Basic principles of stratigraphy
Principle of Uniformitarianism
Principle of Lateral Horizontality
Principle of Superposition
Principle of Cross-cutting Relations
Principle of Inclusions
Principle of Chilled Margins
Correlation
There are many different types of volcanoes beyond the Hollywood version of a tall conical mountain. Some of the main types include shield volcanoes, which are broad with flat tops and low slopes like those in Hawaii; composite volcanoes like Mount Fuji which are tall and steep; cinder cones which are small, steep-sided mounds formed from loose debris; and submarine volcanoes common on ocean floors, which form underwater without disturbing the surface. Fissure volcanoes have cracks that erupt vast quantities of lava to form flat plains rather than a central mountain.
This document discusses migmatisation and metamorphism. Migmatisation is the process where a metamorphic rock like gneiss partially melts and the melt recrystallizes, forming a mixture. Migmatites contain both metamorphic and igneous parts. They often form under extreme heat during metamorphism. Metamorphism transforms rocks through heat, pressure and fluids. Pelitic rocks like shales and mudstones are important in metamorphism as they develop distinctive minerals and commonly produce migmatites at high grades. Migmatites are found widely in Precambrian terranes and the Himalayas.
Stratigraphy is the chronological study of sedimentary rocks to understand the history of the Earth. It involves correlating and arranging rock formations based on principles like lithology, order of superposition, and fossil content. The geological time scale divides Earth's history into Eras, Periods, and Epochs as a framework for studying and comparing rock sequences globally. Today we are in the Holocene Epoch of the Quaternary Period within the Cenozoic Era.
1) There are three main types of meteorites: iron, stone, and stony-iron. Iron meteorites contain over 90% iron and nickel and have a distinctive crystalline pattern.
2) Stone meteorites, which make up the largest group, contain less iron and some contain ancient chondrules. They can resemble terrestrial rocks.
3) Stony-iron meteorites contain roughly equal amounts of iron and stone and include pallasites with olivine crystals and mesosiderites with a silver and black appearance.
This document discusses magmatic differentiation, which is the process by which a single magma can produce a variety of igneous rocks through chemical reactions and mineral crystallization as the magma cools. There are two main branches of differentiation - discontinuous and continuous. The discontinuous branch involves ferromagnesian minerals like olivine and pyroxene crystallizing at discrete temperatures. The continuous branch involves plagioclase feldspars continuously changing in composition as the magma cools. Mechanisms like crystal fractionation, mixing, and assimilation can also cause magmatic differentiation and the formation of rocks with different compositions from a single original magma.
This document discusses factors that affect the viscosity of magma, including temperature, chemical composition/silica content, and amount of dissolved gases. It then provides examples of how viscosity is affected in different lava conditions. Specifically, lava with less silica content and more gases has lower viscosity and can flow farther, while lava with high silica content and fewer gases has higher viscosity and may dome or plug a vent without flowing far. Viscosity decreases with higher temperature and increases with higher silica content or lower gas content.
Metamorphism refers to the process of changes in pre-existing rocks caused by exposure to high pressures and temperatures. There are several types of metamorphism that result from different conditions, including contact metamorphism near igneous intrusions, regional metamorphism during mountain building, and subduction-related metamorphism at convergent plate boundaries. Key agents that control metamorphism are heat, pressure, chemical activity, and fluid phases, which can cause changes in minerals, textures, and introduce new mineral assemblages over long periods of time. Metamorphic grade describes the temperature and pressure conditions, ranging from low-grade to high-grade metamorphism.
This document provides information about the three main types of rocks: igneous, sedimentary, and metamorphic. It describes how each type forms and gives examples. Igneous rocks form from cooling magma or lava. Sedimentary rocks form from compaction and cementation of sediments. Metamorphic rocks form from heat and pressure altering existing rocks. The document also explains key processes that change rocks, such as weathering, erosion, melting and cooling. It introduces the concept of the rock cycle to show how rocks continuously change between the three types.
igneous rocks formation and their classificationMazhar Ali
This document provides an introduction and overview of igneous rocks. It defines igneous rocks as those formed by the solidification of magma or lava. Igneous rocks are classified based on whether they solidified below ground as intrusive rocks or above ground as extrusive rocks. Some common igneous rocks are described, including granite, gabbro, basalt, dolerite, and diorite. Their typical compositions and properties are outlined.
Assimilation is the process by which magma incorporates country rock. As magma passes through the crust, it can break off and melt pieces of the surrounding rock. There are three processes of assimilation: melting, diffusion and dissolution, and reaction. Assimilation requires large amounts of heat from the magma in order to melt the country rock. Evidence of assimilation can be seen in xenoliths and isotopic signatures within the igneous rock. Assimilation affects the composition and evolution of magmas.
The document summarizes the Bowen reaction series, which was developed by Norman Bowen in the early 1900s to explain the order of crystallization of minerals from cooling magma. It describes both the continuous and discontinuous reaction series, with the continuous series involving solid solution minerals like feldspar that adjust composition through diffusion as temperature decreases. The discontinuous series involves minerals like olivine melting at specific temperatures as new minerals begin to crystallize in equilibrium with the cooling magma. The Bowen reaction series and principle help explain how different rock types form from magmas of varying compositions as they cool.
The document summarizes the tectonic framework of India in 3 broad divisions - Peninsular India, Extra-Peninsular India, and the Indo-Gangetic Plain. Peninsular India comprises the Indian shield and its sedimentary basins, and is further divided into the shield areas, mobile belts, and Proterozoic sedimentary basins. Extra-Peninsular India includes the Himalayan mountain ranges, divided into the Lesser Himalayan zone, Central Crystalline zone, and Tethyan zone. The Indo-Gangetic Plain is a deep crustal trough in northern India filled with Quaternary sediments.
This document discusses different types of igneous rocks. It begins by explaining that igneous rocks form from lava or magma and can be extrusive or intrusive. Extrusive rocks form from lava at the surface, while intrusive rocks form from magma underground. Intrusive rocks can take various forms depending on factors like the viscosity of the magma and the structure of the surrounding rock layers. Common intrusive rock forms include dykes, sills, laccoliths, lopoliths, and batholiths. Extrusive rocks include lava flows. The document provides detailed descriptions of these different igneous rock types and their characteristic features.
This document discusses various criteria that can be used to determine the top and bottom of sedimentary beds and identify the relative age of rock layers. Some key criteria mentioned include unconformities, fossils, ripple marks, cross-bedding, graded bedding, and the position of cleavage in folded rocks. Law of superposition, which states that older beds are deposited first and therefore located lower in the stratigraphic column, is also discussed. Together, these criteria can be used to deduce the order of deposition and effects of tilting, folding, or other deformation on sedimentary beds.
A Subsurface Magma Ocean on Io: Exploring the Steady State of Partially Molte...Sérgio Sacani
Intense tidal heating within Io produces active volcanism on the surface, and its internal structure has long been a
subject of debate. A recent reanalysis of the Galileo magnetometer data suggested the presence of a high-meltfraction layer with >50 km thickness in the subsurface region of Io. Whether this layer is a “magmatic sponge”
with interconnected solid or a rheologically liquid “magma ocean” would alter the distribution of tidal heating
and would also influence the interpretation of various observations. To this end, we explore the steady state of a
magmatic sponge and estimate the amount of internal heating necessary to sustain such a layer with a high
degree of melting. Our results show that the rate of tidal dissipation within Io is insufficient to sustain a partialmelt layer of f > 0.2 for a wide range of parameters, suggesting that such a layer would swiftly separate into two
phases. Unless melt and/or solid viscosities are at the higher end of the estimated range, a magmatic sponge
would be unstable, and thus a high-melt-fraction layer suggested in Khurana et al. is likely to be a subsurface
magma ocean.
This document summarizes research on thermohaline convection in porous media. Specifically, it presents:
1) An analysis of thermohaline convection using the Brinkman model, which accounts for non-Darcy effects important at high permeability.
2) Derivation of the linearized perturbation equations governing small disturbances to the initial steady state.
3) Non-dimensionalization of the governing equations and introduction of relevant non-dimensional parameters.
4) The resulting non-dimensional equations are to be solved subject to specified boundary conditions, in order to characterize oscillatory motions in thermohaline configurations of Veronis and Stern types within porous media.
The document provides an overview of mantle plumes and hotspots. It discusses that mantle plumes are columns of hot material rising from deep within the mantle, and hotspots are the surface expression of these plumes seen as volcanic regions. Hotspots have distinct geochemical signatures and are unrelated to tectonic plate boundaries. They can form hotspot tracks as the tectonic plate moves over them, leaving age-progressive volcanic chains. While hotspots were thought to be fixed in the mantle, evidence now suggests they may move slowly relative to each other over geologic timescales. Mantle plumes provide an explanation for various volcanic and tectonic phenomena seen in the interiors of tectonic plates.
Rock deformation is the process by which rocks change shape due to stress and heat. Structural geology studies rock deformation, which can occur through folds, faults, or joints. Folds involve the bending of sedimentary or volcanic rocks into undulating waves, commonly seen as anticlines and synclines or domes and basins. Faults are fractures where the earth's crust is displaced, and include dip-slip, strike-slip, and tensional or compressional faults. Joints are fractures without displacement and include columnar and sheeting joints.
This document discusses metamorphism and metamorphic rocks. It defines metamorphism as the change in rocks due to increases in temperature and pressure. There are different types of metamorphism including contact, regional, and cataclastic metamorphism. Regional metamorphism occurs over large areas and results in strongly foliated rocks like slates, schists and gneisses. The document describes the different grades of metamorphism from low to high and the typical minerals formed. It also discusses structures in metamorphic rocks like foliation and banding. In conclusion, different metamorphic rocks like slates, schists and gneisses have various economic uses as building materials.
This document summarizes the different grades of metamorphism: very low-grade, low-grade, medium-grade, and high-grade. Each grade is defined by the typical temperature and pressure conditions and indicator minerals present. Very low-grade occurs below 200°C and involves minerals like lawsonite. Low-grade occurs from 200-300°C and involves hydrous minerals. Medium-grade occurs from 400-550°C and involves minerals like staurolite and cordierite. High-grade occurs above 600°C and involves breakdown of minerals like muscovite. Isogrades are lines that indicate boundaries of metamorphic grade based on the appearance of indicator minerals.
- Magma forms by partial melting of the mantle or crust and consists of molten or semi-molten rock. It varies in temperature, pressure, density and composition depending on its origin and evolution.
- Magma evolves as it differentiates through fractional crystallization, assimilation, and mixing. Early crystallizing minerals remove elements from the magma, changing its composition over time according to Bowen's reaction series.
- Magma rises towards the Earth's surface where it cools and crystallizes to form either plutonic or volcanic rocks, depending on the cooling rate. Slow cooling results in large mineral crystals in plutonic rocks, while rapid cooling of lava forms volcanic rocks like obsidian with little
Introduction
Stratigraphy is the study of strata (sedimentary layers) in the Earth's crust, it is the relationship between rocks and time.
Stratigrapher are concerned with the observation, description and interpretation of direct and tangible evidence in rocks to determine the history of the Earth.
The combination of sedimentology and stratigraphy allows us to build up pictures of the Earth’s surface at different times in different places and relate them to each other through the relative ages of rocks
A more modern way of stating the same principle is that the laws of nature (laws of chemistry and physics) that have operated in the same way since the beginning of time.
And thus if we understand the physical and chemical principles by which nature operates, we can assume that nature operated the same way in the past.
Basic principles of stratigraphy
Principle of Uniformitarianism
Principle of Lateral Horizontality
Principle of Superposition
Principle of Cross-cutting Relations
Principle of Inclusions
Principle of Chilled Margins
Correlation
There are many different types of volcanoes beyond the Hollywood version of a tall conical mountain. Some of the main types include shield volcanoes, which are broad with flat tops and low slopes like those in Hawaii; composite volcanoes like Mount Fuji which are tall and steep; cinder cones which are small, steep-sided mounds formed from loose debris; and submarine volcanoes common on ocean floors, which form underwater without disturbing the surface. Fissure volcanoes have cracks that erupt vast quantities of lava to form flat plains rather than a central mountain.
This document discusses migmatisation and metamorphism. Migmatisation is the process where a metamorphic rock like gneiss partially melts and the melt recrystallizes, forming a mixture. Migmatites contain both metamorphic and igneous parts. They often form under extreme heat during metamorphism. Metamorphism transforms rocks through heat, pressure and fluids. Pelitic rocks like shales and mudstones are important in metamorphism as they develop distinctive minerals and commonly produce migmatites at high grades. Migmatites are found widely in Precambrian terranes and the Himalayas.
Stratigraphy is the chronological study of sedimentary rocks to understand the history of the Earth. It involves correlating and arranging rock formations based on principles like lithology, order of superposition, and fossil content. The geological time scale divides Earth's history into Eras, Periods, and Epochs as a framework for studying and comparing rock sequences globally. Today we are in the Holocene Epoch of the Quaternary Period within the Cenozoic Era.
1) There are three main types of meteorites: iron, stone, and stony-iron. Iron meteorites contain over 90% iron and nickel and have a distinctive crystalline pattern.
2) Stone meteorites, which make up the largest group, contain less iron and some contain ancient chondrules. They can resemble terrestrial rocks.
3) Stony-iron meteorites contain roughly equal amounts of iron and stone and include pallasites with olivine crystals and mesosiderites with a silver and black appearance.
This document discusses magmatic differentiation, which is the process by which a single magma can produce a variety of igneous rocks through chemical reactions and mineral crystallization as the magma cools. There are two main branches of differentiation - discontinuous and continuous. The discontinuous branch involves ferromagnesian minerals like olivine and pyroxene crystallizing at discrete temperatures. The continuous branch involves plagioclase feldspars continuously changing in composition as the magma cools. Mechanisms like crystal fractionation, mixing, and assimilation can also cause magmatic differentiation and the formation of rocks with different compositions from a single original magma.
This document discusses factors that affect the viscosity of magma, including temperature, chemical composition/silica content, and amount of dissolved gases. It then provides examples of how viscosity is affected in different lava conditions. Specifically, lava with less silica content and more gases has lower viscosity and can flow farther, while lava with high silica content and fewer gases has higher viscosity and may dome or plug a vent without flowing far. Viscosity decreases with higher temperature and increases with higher silica content or lower gas content.
Metamorphism refers to the process of changes in pre-existing rocks caused by exposure to high pressures and temperatures. There are several types of metamorphism that result from different conditions, including contact metamorphism near igneous intrusions, regional metamorphism during mountain building, and subduction-related metamorphism at convergent plate boundaries. Key agents that control metamorphism are heat, pressure, chemical activity, and fluid phases, which can cause changes in minerals, textures, and introduce new mineral assemblages over long periods of time. Metamorphic grade describes the temperature and pressure conditions, ranging from low-grade to high-grade metamorphism.
This document provides information about the three main types of rocks: igneous, sedimentary, and metamorphic. It describes how each type forms and gives examples. Igneous rocks form from cooling magma or lava. Sedimentary rocks form from compaction and cementation of sediments. Metamorphic rocks form from heat and pressure altering existing rocks. The document also explains key processes that change rocks, such as weathering, erosion, melting and cooling. It introduces the concept of the rock cycle to show how rocks continuously change between the three types.
igneous rocks formation and their classificationMazhar Ali
This document provides an introduction and overview of igneous rocks. It defines igneous rocks as those formed by the solidification of magma or lava. Igneous rocks are classified based on whether they solidified below ground as intrusive rocks or above ground as extrusive rocks. Some common igneous rocks are described, including granite, gabbro, basalt, dolerite, and diorite. Their typical compositions and properties are outlined.
Assimilation is the process by which magma incorporates country rock. As magma passes through the crust, it can break off and melt pieces of the surrounding rock. There are three processes of assimilation: melting, diffusion and dissolution, and reaction. Assimilation requires large amounts of heat from the magma in order to melt the country rock. Evidence of assimilation can be seen in xenoliths and isotopic signatures within the igneous rock. Assimilation affects the composition and evolution of magmas.
The document summarizes the Bowen reaction series, which was developed by Norman Bowen in the early 1900s to explain the order of crystallization of minerals from cooling magma. It describes both the continuous and discontinuous reaction series, with the continuous series involving solid solution minerals like feldspar that adjust composition through diffusion as temperature decreases. The discontinuous series involves minerals like olivine melting at specific temperatures as new minerals begin to crystallize in equilibrium with the cooling magma. The Bowen reaction series and principle help explain how different rock types form from magmas of varying compositions as they cool.
The document summarizes the tectonic framework of India in 3 broad divisions - Peninsular India, Extra-Peninsular India, and the Indo-Gangetic Plain. Peninsular India comprises the Indian shield and its sedimentary basins, and is further divided into the shield areas, mobile belts, and Proterozoic sedimentary basins. Extra-Peninsular India includes the Himalayan mountain ranges, divided into the Lesser Himalayan zone, Central Crystalline zone, and Tethyan zone. The Indo-Gangetic Plain is a deep crustal trough in northern India filled with Quaternary sediments.
This document discusses different types of igneous rocks. It begins by explaining that igneous rocks form from lava or magma and can be extrusive or intrusive. Extrusive rocks form from lava at the surface, while intrusive rocks form from magma underground. Intrusive rocks can take various forms depending on factors like the viscosity of the magma and the structure of the surrounding rock layers. Common intrusive rock forms include dykes, sills, laccoliths, lopoliths, and batholiths. Extrusive rocks include lava flows. The document provides detailed descriptions of these different igneous rock types and their characteristic features.
This document discusses various criteria that can be used to determine the top and bottom of sedimentary beds and identify the relative age of rock layers. Some key criteria mentioned include unconformities, fossils, ripple marks, cross-bedding, graded bedding, and the position of cleavage in folded rocks. Law of superposition, which states that older beds are deposited first and therefore located lower in the stratigraphic column, is also discussed. Together, these criteria can be used to deduce the order of deposition and effects of tilting, folding, or other deformation on sedimentary beds.
A Subsurface Magma Ocean on Io: Exploring the Steady State of Partially Molte...Sérgio Sacani
Intense tidal heating within Io produces active volcanism on the surface, and its internal structure has long been a
subject of debate. A recent reanalysis of the Galileo magnetometer data suggested the presence of a high-meltfraction layer with >50 km thickness in the subsurface region of Io. Whether this layer is a “magmatic sponge”
with interconnected solid or a rheologically liquid “magma ocean” would alter the distribution of tidal heating
and would also influence the interpretation of various observations. To this end, we explore the steady state of a
magmatic sponge and estimate the amount of internal heating necessary to sustain such a layer with a high
degree of melting. Our results show that the rate of tidal dissipation within Io is insufficient to sustain a partialmelt layer of f > 0.2 for a wide range of parameters, suggesting that such a layer would swiftly separate into two
phases. Unless melt and/or solid viscosities are at the higher end of the estimated range, a magmatic sponge
would be unstable, and thus a high-melt-fraction layer suggested in Khurana et al. is likely to be a subsurface
magma ocean.
This document summarizes research on thermohaline convection in porous media. Specifically, it presents:
1) An analysis of thermohaline convection using the Brinkman model, which accounts for non-Darcy effects important at high permeability.
2) Derivation of the linearized perturbation equations governing small disturbances to the initial steady state.
3) Non-dimensionalization of the governing equations and introduction of relevant non-dimensional parameters.
4) The resulting non-dimensional equations are to be solved subject to specified boundary conditions, in order to characterize oscillatory motions in thermohaline configurations of Veronis and Stern types within porous media.
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International Journal of Computational Engineering Research(IJCER) ijceronline
nternational Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity.
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2) The shear strain rate and shear heating are highest near the bed but become localized upwards within the ice column to a depth corresponding to the topographic height.
3) Over 50% of the total internal deformation occurs within the localized internal shear band, compared to a more distributed deformation without topography.
4) A nonlinear ice rheology amplifies shear heating effects, overriding vertical cooling
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cover support policymakers and scientists in making well-informed decisions, as alterations in
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help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
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9
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2. Preview
This module presents a calculation of the viscosity of a magma with
varying temperature, water content, and crystal content.
Slides 3-10 give some background on estimates of viscosity in
silicate melts and magmas.
Slide 11 states the problem. What is the density of a hydrous rhyolite
magma?
Slides 12-14 analyze the problem and prompt you to design a plan to
solve it. The problem breaks down into parts: estimating the viscosity
of a rhyolite melt using a statistical model, and estimating the change
in viscosity as crystals are added to the magma.
Slides 15-16 illustrate a spreadsheet that calculates an answer.
Slide 17 discusses the point of the module and provides a broader
volcanological context.
Slide 18 consists of some questions that constitute your homework
assignment.
Slides 19-21 are endnotes for elaboration and reference. 2
3. Background
What is viscosity?
Viscosity is a measure of a fluid’s
resistance to flow. Think of viscosity as a
coefficient that relates the stress applied to
a fluid and the fluids response. For
example:
du1
th
dx2
du1
where t is the stress (Pa), dx is the
2
Photo by L. Connor
resulting velocity gradient in the fluid, and
h is the viscosity (sometimes referred to as This basaltic lava flow emanating
from a very small vent on Mt. Etna is
shear viscosity in this context). about as viscous as a thick salsa.
3
4. Background
What are the units of viscosity?
Consider a fluid trapped between
two plates. When a stress is
applied to the upper plate while the
lower plate is held still, a vertical
velocity gradient is created in the
fluid. This velocity gradient is
equivalent to a strain rate. Since
du1
th Figure from Mader, 2006, Volcanic processes as a source
dx2 of statistical data, In: Mader et al., (eds) Statistics in
Volcanology, Geological Society of London, 1-14.
the units of viscosity are Pascal Please check for yourself that the
seconds (Pa s). units of viscosity must be Pa s, given
the equation and diagram.
4
5. Background
Newtonian and non-Newtonian viscosity
high slope, high viscosity
Any fluid, including silicate
melts, is considered Newtonian
if there is a linear relationship
between stress and strain. That
low slope, low viscosity
is, if:
du1
th
dx2
In a non-Newtonian fluid, the above linear relationship does not hold true. For
example, in a Bingham fluid:
du1
t to h
dx2
where to is a yield stress (also called yield strength) required to “get the fluid
moving”. Although still linear, a new term is added to the linear equation.
5
Make sure you can sketch the stress-strain relationship for a Bingham fluid on the graph.
6. Background
Photo by B. Hill
Why estimate the
viscosity of magma?
Viscosity controls the rate of magma
flow in response to a given pressure
change and the rate at which gas
bubbles and solids (rock fragments
and crystals) move through a magma.
Low viscosity magmas, such as some
basalts, can form very long lava flows
very rapidly. In contrast, rhyolite
magmas are viscous enough to limit
bubble movement. Rather than
escaping by buoyantly rising through
the magma, gas bubbles are trapped
in rhyolite magmas, expand, and
eventually create very explosive The photo shows a mildly explosive eruption of
eruptions. basaltic magma at Cerro Negro volcano,
Nicaragua, in December, 1995. Increasing
viscosity, due to crystal formation and cooling,
contributes to explosive activity. 6
7. Background
What are the viscosities of magmas?
Photo C. Connor
Magma viscosity varies, with temperature, A platinum sphere (density ~21 g cm-3,
water content, and composition, between melting point about 1768 °C) sinking in
NaAlSi3O8 melt at high pressure and high
about 102 Pa s and about 1011 Pa s. That is
temperature (4.2 GPa and 1700°C). From:
nine orders of magnitude! Magma viscosities K. Funakoshi, A. Suzuki and H. Terasaki,
are often determined experimentally, or Journal of Physics :Condensed Matter 14,
measured in the field. 11343-11347 (2002). 7
8. Background
Temperature and Viscosity
Viscosity is highly dependent on
temperature. Think of a pool of molten
glass. As the temperature drops, it will
take more and more applied stress to
make the glass flow.
An Arrhenian model of viscosity is one in
which viscosity is exponentially
dependent on temperature: This glass is an alkaline silicate melt
with low viscosity at 1000 °C and very
E “workable” into shapes at about 800 to
h(T ) ho exp
RT
900 °C. At about 700 °C, the viscosity
is high enough for the shape to not
deform under its own weight.
where ho is viscosity under standard Learn More about the
temperature conditions, E is the Arrhenian model
activation energy, R is the universal gas
constant, and T is temperature. Learn More about E/RT 8
9. Background
For most silicate melts, even Arrhenian models do not work!
Over the last 25 years, magma Water “de-polymerizes” melts,
physicists have discovered silicate changing their viscosities.
melts are often non-Arrhenian,
largely because of the additional
impact of water on viscosity. Water
breaks chains of silica polymers in
melts, and the shorter polymers
result in a lower viscosity. One
non-Arrhenian model of viscosity is
in the form of the Vogel-Fulcher-
Tammann (VFT) equation:
b( H2 O)
log h(T , H2 O) a( H2 O)
T c( H2 O)
where a, b, and c are constants that
must be determined for specific
melt compositions using lab
experiments. Images created by Bill Rose 9
10. Background
For silicate magmas, even non-Arrhenian models do not work!
Even when coefficients a, b, and c are estimated for the VFT
equation for a specific melt composition, other factors can
strongly influence viscosity. Picture the sudden onset of
crystallization, a virtual snowstorm of microlites (small
feldspar crystals) in an ascending magma. These crystals
increase the bulk viscosity of the melt-crystal mixture.
Viscosity of the melt-crystal magma
mixture can be estimated with:
52
hmagma 1
hmelt
o
where is the volume fraction of crystals
and o is known as the maximum packing
fraction of a solid. Microlites in a now frozen magma
10
11. Problem
Calculate the viscosity of a rhyolite melt with 2 weight percent
water at 900 °C and with 0.03 volume fraction crystals.
Use a form of the VFT model to
solve the problem.
More generally, it is useful to
use the VFT model to explore
the nature of rhyolite magma
viscosity. Namely, how does
viscosity vary as a function of:
• Weight percent water?
The volcanic Isla San Luis off the coast of Baja, California,
• Temperature? has a Holocene rhyolite dome at its center. The dome is the
• Volume fraction of crystals in mass of dark rocks forming a steep mound, indicative of the
high viscosity of this magma when it erupted. (Photo from
the magma? the Smithsonian Global Volcanism Network webpage).
11
12. Designing a Plan, Part 1
Given the water content, Give answer in Pascal
temperature, and volume seconds (Pa s).
fraction of crystals in the
magma, calculate the
viscosity. Notes:
(1) Coefficients used in the VFT model remain
to be determined at this stage.
You will need to: (2) Different models for calculating magma
viscosity from melt viscosity exist; a
• implement the VFT comparatively simple model based on
model to solve for melt spherical “crystals” will be implemented
viscosity. here.
(3) This VFT model is actually compositionally
• calculate the magma specific, it is only valid for leucogranitic
viscosity from melt melts. A leucogranitic melt is a rhyolitic
viscosity, given the magma enriched in aluminum, often
volume fraction of characterized by biotite phenocrysts and a
crystals suspended in pale colored groundmass.
the magma.
12
13. Designing a Plan, Part 2
Calculate the melt viscosity.
We need to put the VFT model into practice.
A form of the VFT model proposed by Hess and Dingwell (1996, Viscosities of hydrous leucogranitic melts:
A non-Arrhenian model, American Mineralogist, volume 81, 1297-1300) is used to solve the problem.
Hess and Digwell (1996) found a best-fit regression model for
non-Arrhenian viscosity: The values of these
b1 b2 ln( w)
coefficients are:
logh a1 a2 ln( w)
a1 = -3.54
T c1 c2 ln( w)
a2 = 0.83
b1 = 9601
b2 = -2366
where h is viscosity, w is weight percent water, T is temperature (K), c1 = 196
and a1, a2, b1, b2, c1,and c2 are coefficients of their regression c2 = 32
model.
Hess and Dingwell estimated the values of the coefficients in
the model by regression. That is, they found the best-fit
values of these six coefficients using data from 111 viscosity Learn more
experiments conducted at various temperatures on rhyolites about regression
with various water contents between 0.2 and 12.3 wt % and
temperatures between about 750 K and 1473 K. Their model
is not valid for other conditions! 13
14. Designing a Plan, Part 3
Estimate how the viscosity changes with Recall that melt is by
the addition of crystals to the magma. definition a liquid,
whereas magma contains
The change in viscosity of a melt, with the addition of solid melt + solids and gas.
particles like crystals or xenoliths, is a complex problem. A
simplified answer is provided by the following equation.
5
1
hmagma hmelt
2
o
Here the crystals are taken to be spheres (not a particularly good
assumption about the shape of many crystals, but a good leading Approaching the maximum
order approximation nevertheless). The viscosity then changes packing fraction in a melt
according to a power law. As the crystal spheres become more populated with “ideally
abundant, they pack closer together until they occupy much of spherical” crystals. Although
the total volume, with melt only left in the open spaces between the “crystals” are densely
spheres. This is the maximum packing fraction of the solid, o. packed, there is still room for
Assume o = 0.6 melt in the gaps.
14
15. Carrying Out the Plan: Spreadsheet to Calculate the Viscosity
B C D E F
2 Calculate the Viscosity of a Rhyolite Magma using the VFT Model
3
4 Coefficients of the VFT Model A cell containing a
5 a1 -3.54
number that is given
6 a2 0.83 information
7 b1 9601
8 b2 -2366
9 c1 196 A cell containing a number
10 c2 32 that is a constant for this
11 problem
12 Max. packing
13 fraction (Ø o ) 0.6
14
15 Given Conditions
A cell containing a
16 Temperature (K) 1173
17 Water Content (wt %) 2
formula
18 Vol. fraction of crystals 0.03
19
20 Calculated results
21 log (melt viscosity)(Pa s) 5.37303
22 melt viscosity (Pa s) 236064.1
23 magma viscosity (Pa s) 268361.9
At this point, be sure to implement this spreadsheet and check
that your formulas duplicate the values shown. You will need
this spreadsheet to complete the end-of-module assignment.
15
16. Carrying Out the Plan: Spreadsheet to Calculate the Viscosity
B C D E F
2 Calculate the Viscosity of a Rhyolite Magma using the VFT Model While the calculation of a single viscosity value
3
4 Coefficients of the VFT Model is useful, it does not allow you to see trends.
5 a1 -3.54 The spreadsheet is easily modified to show
6 a2 0.83
7 b1 9601 results of numerous calculations graphically.
8 b2 -2366
9 c1 196
10 c2 32 Add cells to your spreadsheet so you
11
12 Max. packing
can graph results and observe trends.
13 fraction (Ø o ) 0.6
14
15 Given Conditions
A cell containing a
16 Temperature (K) 1173 number that is
17 Water Content (wt %) 2
18 Vol. fraction of crystals 0.03
given information
19
20 Calculated results
21 log (melt viscosity)(Pa s) 5.37303
A cell containing a
22 melt viscosity (Pa s) 236064.1 formula
23 magma viscosity (Pa s) 268361.9
24
25 Log (Melt Viscosity) (Pa s)
26 Temperature (K) 10
27 water content (wt %) 1000 1200 1400
Log (viscosity) (Pa s)
28 0.5 9.490653 6.838885 5.052167
9
29 1 8.401542 6.022749 4.434252 8
30 1.5 7.721182 5.516466 4.052193 7
31 2 7.217990 5.143743 3.771548 6 1000 K
32 2.5 6.815539 4.846682 3.548257 5 1200 K
33 3 6.478611 4.598688 3.362109 4
34 3.5 6.187923 4.385241 3.202084 1400 K
3
35 4 5.931723 4.197508 3.061484
36 4.5 5.702294 4.029700 2.935923
2
37 5 5.494286 3.877809 2.822367 1
38 5.5 5.303829 3.738944 2.718627 0
39 6 5.128033 3.610943 2.623071 0 2 4 6 8 10
40 6.5 4.964677 3.492150 2.534447
41 7 4.812019 3.381267 2.451773 Water Content (wt %)
16
42 7.5 4.668662 3.277256 2.374266
43 8 4.533474 3.179272 2.301290
17. What you have done
You have calculated the viscosity of a hydrous rhyolite magma using the non-Arrhenian
VFT model and a simplified model to account for volume fraction of crystals.
The viscosity of silicate melts is fundamental to the nature of magma transport. Viscosity controls the form
of lava flows and strongly contributes to the nature of volcanic eruptions. In fact, viscosity is a powerful
constraint on the nature of many geological phenomena, such as convective flow in the mantle, the
deformation of the ductile lower crust, and particle transport in the atmosphere and in rivers.
You have discovered that it is possible to estimate the viscosity of magmas using highly nonlinear models
that account for the affects of temperature, water content, and volume fraction of crystals.
Although based in physical principles, these models are statistical in nature. That is, the coefficients of the
VFT model were estimated from experimental data using a sophisticated regression technique. It is likely,
therefore, that these models will improve with additional experiments. In addition, it is clear that it is
inappropriate to use such models outside of the range of experimental data from which they are derived.
Useful papers that discuss magma viscosity in detail:
Shaw, H.R., 1972, Viscosities of magmatic silicate liquids: An empirical method of prediction. American
Journal of Science, 272, 870-889. (Shaw was one of the first people to discuss the relationships between
thermodynamic properties of silicates and physical properties of magmas).
Hess, K-U., and D.B. Dingwell, 1996, Viscosities of hydrous leucogranitic melts: A non-Arrhenian model,
American Mineralogist, 81, 1297-1300. (the VFT method used in this module)
Spera, F., 2000, Physical properties of magma, In: Sigurdsson et al., eds., Encyclopedia of Volcanoes,
Academic Press, 171-190. (an accessible discussion)
17
18. End of Module Assignments
1. Make sure you turn in a spreadsheet showing the worked examples.
2. Plot a graph that shows the dependence of rhyolite magma viscosity on crystal content for
hydrous melts H20 = 2 (wt %), 6 (wt %), and 12 (wt %) at 900 °C. Now consider a magma
rising through a volcano conduit. How does water content, crystal content, and temperature
affect the rate of ascent, all other things being equal? Which factor would you say is most
important and why?
3. Each of the six coefficients (a1-c2) used in the VFT model is estimated. Suppose the error in
these estimates is about 20%. That is, the coefficients could be 20% lower or 20% higher
than the values reported here. Given this uncertainty, what is the range of viscosities that you
estimate for a rhyolite melt that is 4 weight percent water at 900 °C.
4. The viscosity of some brands of peanut butter is about 8000 Pa s. Use your spreadsheet to
investigate the range of conditions (water content, temperature, crystal content) under which
rhyolite magmas would have approximately this viscosity.
5. What happens to the viscosity of peanut butter when you add whole peanuts to the mixture?
Why?
6. The ‘obsidian problem’ refers to the fact that some rhyolite magmas reach the surface very
quickly, but do not erupt explosively. Rather, they form effusive eruptions that make lava
domes of very glassy (crystal poor) lava. Use your spreadsheet to investigate this problem.
Under what circumstances might rhyolite magmas form such domes rather than erupt in a
spectacular explosion?
18
19. More about the Arrhenian Model
The Arrhenian model is named for Svante Arrhenius, who
developed a method of predicting the increased speed of a
chemical reaction with increased temperature. His equation has
the form:
E
k A exp
RT
More about E,R,T
where k is the rate coefficient that describes how much faster the reaction will
proceed, A is the Arrhenius coefficient, which varies with the specific chemical
reaction, E is the activation energy, R is the gas constant, and T is temperature.
Note that this is the exact form of the Arrhenian viscosity model, with A replaced
by the viscosity of the fluid at some standard temperature condition.
Arrhenian models are also common in statistics and used to predict the higher
rate of failure of just about anything at higher temperatures. For more about
the statistical application of the model, see:
http://www.itl.nist.gov/div898/handbook/apr/section1/apr151.htm
19
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20. ERT
E stands for activation energy, literally the energy “hump” or barrier, which must be
overcome for a reaction to proceed. In viscosity, the energy that must be applied to
get it all flowing. The unit of activation energy is the joule mol-1, that is, the energy
required to get one mole of substance to react, or flow.
R stands for the universal gas constant and is equal to Boltzmann’s constant x
Avagadro’s number. R relates energy to temperature, T. The units of Boltzmann’s
constant, found experimentally are joule per K, k = 1.380 x 10−23 J K-1, so the
universal gas constant is R=8.314 J mol-1 K-1.
Prove to yourself that E/RT is dimensionless. What happens to E/RT as
T increases but the activation energy remains constant? What happens
to the value of exp[-E/RT] as T increases?
So in the Arrhenian model, the energy required to make the fluid react (in this
case react by flowing) under standard conditions is constant. The viscosity
decreases with temperature because the ratio –E/RT decreases with
increasing temperature. Remember, this is only a model, because in reality
what is happening is that the number and length of silica polymer chains is
decreasing with increasing temperature. The model is a symbolic, in this
case mathematical, representation of reality.
20
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21. The Nature of Regression
In statistics, regression is used to determine the relationship between two or more
variables. This relationship is usually characterized by the magnitude of
coefficients. For example, in linear regression, y= mx +b, the relationship between
variables y and x is determined by the magnitude of the coefficients m and b.
Uncertainty exists in any regression
model, because the relationship
between variables is not ideal. In the
plot shown, the relationship between
cumulative volume and time looks
linear, but there is “certainly uncertainty”
(i.e., measured points plot off the line).
The best-fit line is a statistical model,
that is, a model that includes some
A linear regression showing the relationship between
component of random (or unexplained) two variables (time, and cumulative eruption volume)
variation. When we use a statistical for eruptions of Cerro Negro volcano, Nicaragua.
Actual values are plotted as solid circles, the line is
model to estimate viscosity, we accept the best-fit regression. Data from Hill et al., 1998,
the fact that some random variation will GSA Bulletin.
not be accounted for by the model!
21
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