GEOL100 Exam 2

How can a volcanic neck form

- can form as erosion wears down a volcano - could be formed beneath the volcano that was excavated by a large explosion and erosion remove sthe crater and hundreds of meters of rock

factors which cause melting

heat transfer, adding volatiles, decompression

upwelling

means material is still molten

sizes of clastic sediments

- check picture of table (page 178) largest class are boulders at 0.25 m long cobbles smaller than boulders about size of softball pebble- can be held comfortable in hand sand- smaller than 2 mm clay and silt finer than sand and compost mud

Physical weathering

- for some reason book and lecture notes don't match up, check notes for some traits, others are listed below. Near Surface Fracturing- many processes near surface break rock into smaller pieces. Also occur when rocks expand as they are uplifted and exposed to less pressure. Frost and Mineral wedging- rocks can be broken as water freezes and expands fractures. crystals of salt and others minerals can also do this Thermal Expansion- rocks heated by wildfires and the sun can expand and crack irregularly, plays a very minor role. Biological activity- roots can grow downward into fractures and pry rocks apart

What made Earth Hot?

- materials formed early planet and became hot as they collided and were compressed under force of gravity. -earth grew in size and became larger target for asteroids and meteoroids attracted by gravity. energy of impacts heated the surface more. -Early in history, Earth mostly molten. Masses of iron and nickel, were pulled by gravity to planets core because of large density, adding heat as they sank

Characteristics of a volcano

- vent where magma and other volcanic products erupt onto surface -most volcanoes have a crater near the top of volcano -volcanic rocks which form from lava, pumice, volcanic ash -magma erupts from fissures and circular depressions called calderas - not every hill is a volcano, must have most of these features

Mount Rainier

- volcano above Tacoma, dangerous composite volcano -mud flow is a very large possibility, the greatest volcanic hazard in the cascade range according to the US geological survey -lava flow hazards are mostly near the volcano itself -Cascade range have been erupting more recently in the past 200 years and most are dangerous composite volcanoes. Juan de fuca plate is subducting beneath the continental crust of western north America, where all of these volcanoes lie.

How is magma generated in subduction zone?

1. when oceanic plate converges with another oceanic place, subduction occurs 2. in response to changes in pressure and temp, minerals in subducting plate convert into new ones through metamorphism, Water liberates from minerals and lowers the melting temperature of the mantle above subducting plate. If temp high enough, melting occurs

Obsidian

A shiny volcanic class that is normally medium gray to black color. forms when lava flow cools too rapidly to form crystals. Commonly has bands and some phenocrysts or fragments. Mostly felsic

Processes involved in forming igneous rocks

Begins with magma forms by melting at depth, followed by movement of the magma toward the surface and then solidification of the magma into solid rock.

Mt. St Helens eruption

Composite volcano, blew up out of side and top, since eruption magma created a lava dome

What causes the mantle to melt at a divergent plate boundary?

Decrease in pressure felt by the rising mantl

Felsic

Describes magma or igneous rock that is rich in feldspars silica and quartz and that is generally light in color.

Convection

Flow of a liquid or by a solid but weak material, can flow in a circular path known as convection cell. Example: as solid asthenosphere rises beneath mid-ocean ridge, it brings hot rocks upward by convection, adding material to oceanic lithosphere

Conduction

Heat transfer by direct contact. Example: hot, newly created lithosphere begins to cool by conduction of heat to adjacent cooler rocks and seawater

How do thermal vibrations and pressure affect a mineral lattice?

In solids, atoms and bonds are always vibrating, and temperature increases vibrations. When vibrations become to strong, bonds break and melting begins. Increase in pressure has opposite affect and compresses solid.

4 ways that magma erupts

Lava flows and domes: -erupts through vent and creates lava flow and can be fairly fluid - lava dome forms from eruption of highly viscous lava due to high silica content to pile up around vent. Pyroclastic eruptions: lava fountain- explosive eruption sending molten lava into the air resulting from high initial gas content in a less viscous lava airborne material is called tephra that can create volcanic ash which forms when bubbles blow apart bits of magma

Features of lava flows

Lava tubes, AA, Pahoehoe, check notes for more information

Gabbro

Mafic, coarsely crystalline. typically dark and consists of pyroxene and other mafic minerals along with light-gray, calcium-rich plagioclase feldspar. Feldspar-rich varieties are lighter colored, and some gabbro has olivine

Factors that influence how far a magma rises toward surface?

Magma Pressure pushes magma through openings Density- less dense will rise Gas Pressure, decreasing pressure allows bubbles to form in magma and therefore density decreases stress, tectonic stress can help magma open steep fractures to provide pathway or can trap magma.

Types of Sediment environments

Mountain- steep slopes and provides abundant sediment and can be transported out of mountains to other settings Streams- steep gradients in mountains but develop a braided appearance defined by channels that split apart and region, fluvial process. Sand dunes- wind picks up and moves sand grains and finer particles to form fields of sand dunes Delta- piled up sediment from streams that enter a standing body of water such as an ocean or lake Beaches, swamps, bogs pretty self explanatory

Processes by which magma cools

Reaches land surface transfers thermal energy through conduction and radiation. At depth, loses thermal energy through conduction Can release gases, including water vapor Water in rocks can receive heat by conduction Magma solidifies when minerals crystallize or glass forms slow cooling- coarse grained Fast cooling- very fine grained

Where does magmatism occur away from plate boundaries?

Rifts in continental interiors product basaltic lava and could be caused by decompression melting as the asthenosphere rises in response to stretching of overlying plate and can split continent in two, asthenosphere can melt the lithosphere mantle derived magma accumulates in magma chambers in continental crust and may heat the crust to melt parts of it, which can yield felsic magmas while mafic magmas get trapped in the lower parts of the continental crust and solidifies.

volcanic breccia

Rock formed from large pieces of volcanic rock (cinders, blocks, bombs). can be almost any composition

How are pressures and temperatures determined in the laboratory?

Scientists place a small sample of the rock in a special oven and raise the pressure to an amount equal to some pressure and is then heated to a specific temperature and held at this state for a given time. At the end, scientists will inspect sample for signs of melting or solidifying. Repeated at different temp/pressure and plotted on graph

Four main type of volcanoes

Scoria cone, shield volcano, composite volcano, volcanic dome (check notes for details of each)

Ages of scoria cones and lava flows

Scoria cones- young if little vegetation on them and are commonly associated with dark, fresh-looking lava flows Lava flow- steep flow front, top of flow is typically rough and displays features of AA and pahoehoe

Bowen's Reaction Series

Shows the sequence in which different silicate minerals form during the progressive cooling of a mafic melt.

Chemical Composition of Igneous Rocks

Silica main ingredient in felsic 44-77% Granite contain 70-77% Silica 44-50% in mafic mafic contain more magnesium, iron, and calcium Intermediate rocks contain 60% silica, contain magnesium, iron, calcium, potassium, feldspar, including amphibole and biotite

Phaneritic

Slow cooling, large crystals, coarse grained

Pressure and Temperature conditions

Temperature Low -> High x axis Temperature low down to high on y axis left of melting curve is solid, melting curve is angled down towards 4th quadrant and position depends on composition of the rock. If a rock is directly on melting curve, it is in the process of melting or solidifying. adding water can significantly lower the temperature at which a rock will melt and moves the melting curve to lower temperatures.

pyroclastic flow

The expulsion of ash, cinders, bombs, and gases during an explosive volcanic eruption, considered welded.

An igneous rock has a medium-gray, fine-grained matrix with large crystals of plagioclase. Which of the following statements about it is FALSE

The lava flow that produced it was quenched in ocean water

Heating Earth with Radioactive Decay

Three types of decay: alpha, beta, and gamma decay. Alpha most important. Accounts for most of earth's total thermal energy

fraser river valley

Valleys in mountains contain lakes and steep mountain streams that carry sediments which disperse into the sea and gradually settle to the sea bottom creating a delta near the mouth of the river

columnar joints

a pattern of cracks that forms during cooling of molten rock to generate columns

lahar

a volcanic mud and debris flow that resembles fluid concrete

shield volcano

a wide, gently sloping mountain made of layers of lava and formed by quiet eruptions. (find more information in notes)

Types of rocks that form on mid-ocean ridges

all mafic, Sea Pillow Basalts Sheeted Dikes Gabbro(magma chamber) Mantle and ultramafic rocks

magma chamber

an underground body of molten rock. can consist of multiple influxes of magma, early formed minerals can remove chemical components from magma and may rise of sink. can mix with magma or distinct and adds new thermal energy. can create a cycle of minerals melting into magma that may partially melt wall rocks forming even more new magma which can be assimilated into the existing magma.

Shapes of clasts

angular- sharp edges from mountains rounded- smooth curved surfaces from water

Burial of sedimentary rock

as its buried, pressure is increased and pushed clasts together called compaction. Sand grains are loose on surface and contain pore spaces between grains filled with air or water. Weight of overlying sediment decreased pore space and the layer of sand loses thickness. Clay particles completely push together and can compact much more than sand to almost half its original thickness. cementation- some openings remain after compaction, dissolved materials can precipitate to form minerals that act as natural sediment. See notes for specific minerals that commonly act as cement.

How does transportation affect sediment?

as large clasts and boulders are transported, they can easily be broken apart. Silt sand and other larger clasts carried in water can cause abrasion of the clasts in a channel

How does nonwelded volcanic ash form?

ash that erupts vertically in a column and cools significantly before accumulating on the surface.

gamma decay

atom emits an energetic particle called a photon

What composition of magma do shield volcanoes produce

basalt

ocean divergent boundary has what type of lava composition

basalt

ocean-ocean convergent boundary has what type of lava composition

basalt

Floor Basalts

basaltic lava flows covering vast areas. they erupt along a linear fissure which can create large volume flows the thicker the fissure due to its low viscosity magma. It does not erupt from a single central volcanic vent but like a string of vents. locations include Columbia plateau, southeaster coast of south America, Greenland, Siberia, India (the deccan traps), and near Antarctica (kerguelen plateau). Eruptions release large amounts of sulfur dioxide and therefore can lead to atmospheric cooling changing the entire Earths climate

Granite can be found in

batholith

Environments near Shorelines and oceans

beaches- stretches of coastline along which sediment has accumulated, containing mostly sand rounded gravel cobbles or shells. lagoon- sheltered water by offshore reefs that is commonly shallow calm and even warm. They contain sand mud and stones from land, think of OC west side. Reefs- parallel to coasts, encircle islands and protect shoreline from large waves Submarine canyons- slopes that funnel sediment towards deeper waters. Deep seafloor- usually receives less sediment than areas closer to land, sediment dominated by fine, windblown dust and remains of single-celled marine organisms. coastal dunes- sand and finer sediment built up from win Tidal flats- low areas flooded by the seas covered by mud and sand that can be rocky. Can accumulate salt and other evaporite minerals Submarine deltas- extended deltas several kilometers offshore. Muddy and sandy sediment can be sent to deeper water on the slopes Barrier islands- accumulations of sand rise above the shallow coastal waters as long narrow islands.

What controls size shape and sorting of clasts?

bedrock exposed on mountains or cliffs breaks off to form large boulders and angular. get rounded as transported through water 4 factors that influence transportation sediment type steepness of slope, sediment supply, strength of current, agents of transports can all affect size shape and sorting.

laccolith

bulge shaped magma body that was inflated through gently inclined layers. Look kind of like bubbles in the earth

Layers in sedimentary rocks

can be distinct because of different grain sizes than adjacent layers and can have different compositions than other layers. Boundaries between them can be very sharp or gradational depending on how it was formed. can form from a variety of ways discrete event such as a flood change in current sediment supply sea level change climate change

The hot springs in Yellowstone are most likely to form which type of sedimentary rock?

chemical

Lithified detritus (breakdown products of preexisting rocks) forms which kind of sedimentary rock

clastic

Granite

coarsely crystalline, light-colored igneous rock. Felsic minerals of feldspar and quartz. can contain biotite and some contain mica.

Peridotite

coarsely crystalline, ultra-mafic rock. Contains more magnesium rich and iron rich minerals. especially green olivine and dark pyroxene. UPPER MANTLE IS COMPOSED OF PERIDOTITE

Breccia

coarsest clastic sedimentary rocks that contains angular clasts. forms massive layers lenses or wedges. originate in mountains and flow down steep slopes and through canyons or can represent a type of landslide. Can also form from steep mountain streams that deposit sediment along the mountain front, called an alluvial fan.

Three mechanisms of Heat transfer

conduction, convection, radiant heat transfer

Most of the igneous rocks within oceanic abyssal plains are

covered by pelagic sediments

How are igneous rocks classified?

considers composition and size of crystals of the rock. Use screenshot of table

Scoria

dark gray, black, or reddish volcanic rock that contains many vesicles/ It usually has the composition of basalt or andesite.

Basalt

dark mafic lava rock. Most basalt is dark gray to nearly black, and some have vesicles. Can contain some phenocrysts of dark pyroxene, green olivine, or cream colored plagioclase feldspar.

Mafic

describes magma or igneous rock that is rich in magnesium and iron and that is generally dark in color

A sedimentary rock composed of well-sorted sand-sized particles with cross-beds likely formed in a ________ environment

desert

Difference between dike and sill

dike- sheet-like intrusion that cuts across any layers present in the host rocks, steep and rise vertically sill- an intrusion that is parallel to layers in host rocks, most sub-horizontal and form by pushing adjacent rocks upward rather than sideways

Where do large magma chambers form?

form above hot spots and within mid ocean ridges in oceanic lithosphere. form above subduction zones on continents or within oceanic island arcs. hot spots and rifts within continents, continental collisions can trap large amounts of magma at depth

Ophiolites

distinctive rock sequence of sliced oceanic crust and is identical to newly formed oceanic crust except it contains additional layer of oceanic sediment on top

How does magma form in continental collisions

do not reach surface. one continental plate may slide beneath the other and heat up with increased pressure. Water may be released by metamorphism and if descending plate gets hot enough, will undergo partial melting producing felsic magmas. partial melting leaves behind mafic minerals and makes lower crust more mafic

Difference between eruption column and pyroclastic flow

eruption column is magma blown apart by volcanic cases and can erupt high into the atmosphere which falls back down the earth, pyroclastic flow does not jet straight up but collapses down the side of the volcano as a dense hot cloud of ash and particles.

Mauna Loa and Kilauea

extremely active volcanoes in Hawaii, most recent eruption was in 1984. Kilauea considered the home of pele the volcano goddess and is even more active and has been erupting nearly nonstop since 1983.

Pegmatite

extremely coarse-grained igneous rock, forms if magma is relatively water rich, can be any composition

Aphanitic

fast cooling, small crystals, fine grained

The order in which minerals crystallize from magma

felsic melt before mafic mafic crystallize before mafic High temp to Low Temp olivine pyroxene amphibole biotite muscovite K-feldspar Quartz Slower cooling, more crystals

Rhyolite

fine grained felsic rock. mostly finely crystalline, but can contain glass, volcanic ash, pieces of pumice, and variable amounts of visible crystals of quartz, k-feldspar, or biotite

Andesite

fine grained intermediate. Commonly gray or greenish, can have slight maroon or purplish tint. Commonly has phenocrysts of cream-colored feldspar or dark amphibole

As compared to phaneritic igneous rocks, aphanitic rocks are

finer grained

Where do coarse grained igneous rocks form?

form at greater depths, where magma cools at a rate that is slow enough for large crystals to grow

How can melting influence composition of magma?

formation of crystals, melting of rocks adjacent to the magma chamber, and mixing of two different types of magma.

The Valles Caldera

formed when a huge magma chamber erupted, covered the region in volcanic ash. The underground magma chamber collapsed, forming circular caldera and slow moving lava flows built up dome-shaped hills surrounding the caldera.

Volcanic Glass

forms when magma erupts on the surface and cools so quickly that crystals do not form.

Basaltic eruptions

gases carry bits of lava into the air forming a lava fountain. these airborne bits cool and then fall around vent of scoria. fluid basaltic lava pours from the vent and downhill. occurs in SCORIA CONES.

How can mudflow be detected

geoscientists use a network of remote monitoring stations to detect characteristic rumble made by mudflows as they rush down valleys

Which environment would be most likely to produce a sedimentary rock that is composed of an unsorted mix of clast sizes from silt to cobble?

glacial

Pillow Basalt

glass-encrusted basalt blobs that form when magma extrudes on the sea floor and cools very quickly

Types of bedding

graded, cross- form in sand dunes based on wind, parallel- most common (self explanatory)

White mountain batholith

granitic rocks form high peaks. Consists of several dozen individual plutons that represent separate injections of magma at different times each with different shapes ranging from cylindrical to curved dikes. related to a hot spot that melted its way into continental crust

Difference between hazard and risk

hazard- existence of a potentially dangerous situation or event risk- an assessment of whether the hazard might have some societal impact

Radiant heat transfer

heat radiates through the air

A sedimentary rock composed of finely laminated silt and clay with alternating light and dark layers likely formed in a _________ environment

lake

Yellowstone

large active volcano that has experienced three huge, caldera-forming eruptions. average time between eruptions is about 700,000 years, 640,000 has passed since last eruption.

Crater Lake

large caldera formed 7700 years ago and is now a lake. Eruption was more than 50 times larger than Mt. St. Helens

Caldera

large crater/depression that can spread volcanic ash over huge areas. includes granite and trapped tephra make up what is within and outside of calderas along with rhyolite domes. Layers: tuff and pyroclastic deposits ash and pumice crystalline granite and porphyry represent crystallized magma chamber

What regions have highest risk for volcanic eruptions

largest concentration of composite volcanoes is along the pacific ring of fire. Shield volcanoes occur along lines of islands and submarine mountains much fluid basaltic lava erupts on seafloor at mid ocean ridges, that pose little to no risk. Basalt flows, scoria cones, and composite volcanoes are in the middle of continents over hot spots or in continental rifts.

Sizes of volcanoes

largest to smallest large shield, composite volcano, small shield, dome, scoria cone

How does gas influence eruption

less gas creates pyroclastic flows because eruption columns need a lot of built up gas to explode directly into atmosphere.

how can volcano cause flood

location near large glaciers, can cause a flood of meltwater

Common nonclastic sedimentary rocks

look at picture or page 183, too many to take notes of

How can assimilation influence magma?

mafic magma is hotter than the melting temp of felsic rocks so it can melt felsic wall rocks. this is called assimilation and include both felsic wall rocks and mafic magma

How can crystallization influence magma

mafic minerals crystallize first, making remaining magma less mafic and partial crystallization of a mafic magma typically produces a magma of more intermediate composition. heavy mafic materials will settle to the bottom and upper magma more felsic which will float upward as it is less dense.

How do porphyritic textures form?

magma needs sufficient time in subsurface magma chamber to grow visible crystals, then magma rises to just below or on surface where the rest of the magma solidifies rapidly

Subduction derived magma encounters overlying crust

magmas rise into overriding plate and modify the crust they encounter. most subduction related magma never reaches surface but some erupts forming clusters or volcanoes. If continental, volcanoes are part of mountain belt. If oceanic, individual volcanoes on island arc are formed at intermediate composition in each

seismic measurements

measures ground shaking which is from magma moving expanding or contracting and therefore exerting a force on surrounding rocks

Complete process of forming igneous rock

melts 40-150km beneath surface, in deeper crust of mantle called the source area. Complete melting is rare and most magmas result from partial melting. magma accumulates to form magma chambers. Igneous rock that solidified at a considerable depth is referred as a plutonic rock, such as granite and granodiorite. magma rises through crust, stops or passes through magma chambers. Body of molten rock in subsurface called intrusion and igneous rock that solidifies below surface called intrusive rock. some magma may crystallize in chamber, while some rises to the surface and may carry early formed crystals forming porphyritic rock. magma reaches surface or erupted through volcano. Igneous rock formed on surface is called extrusive rock or volcanic rock.

Chemical and biochemical rocks are classified primarily on the basis of

mineral composition

Diorite

more mafic than granite, it is intermediate between felsic and mafic compositions. contains plagioclase feldspar and amphibole, and can contain biotite or pyroxene.

Laki

occurred in Europe and released a large amount of ash and sulfur dioxide gas. largest recorded eruption and dimmed sunlight for the entire summer. Changed the climate for the next three years

Where do fine grained igneous rocks form?

occurs when magma solidifies on the surface in a thick lava flow or at shallow depths beneath the surface. Medium grained rocks form deeper

Why does melting occur along mid-ocean ridges and mafic?

older crust moves away along ridge magma rises upward through magma filled fractures buoyant, mafic magma rises away from unmelted residue and creates magma chambers in crust as plates separate, asthenosphere rises to fill area and pressure decreases so the rock partially melts mantle high temp allows mantle rocks to flow as a weak solid while maintaining crystalline structure

chemical weathering

one extra process biological reactions- decaying plants produce acids that can attack rocks, and some bacteria consume certain parts of rocks. cause minerals to break down

Conglomerate is

poorly sorted

How can magma mixing influence magma?

produces magma that has a composition intermediate between the two magmas that mixed, boundary between two materials will be irregular

What areas around volcano have highest risk

proximity, valleys, wind direction, particulars

Bombs, ash, and cinders are all examples of

pyroclastic debris

when melt has just begun to crystallize, what will grow first

pyroxene

Beta Decay

radioactive decay in which an electron is emitted.

types of sorting

range of clasts in sediment, poorly sorted, moderate sorting containing sand and small pebbles, well sorted such as sand dunes

Sea level falls locally, and terrestrial sediments are deposited on top of marine sediments during events termed

regressions

Three ways in which magma rises through crust

rises through crust by traveling through a fracture, forming a fissure, and can solidify to form a sheetlike feature called a dike. Magma can also move through the crust by removing the overlying rocks and also from tectonic forces

Mantle plume

rising plume of hot mantle material. in ocean- magma generated by mantle encounters lithosphere, it spreads along the boundary. it can reach the surface and create large volcanoes at the seafloor in continent- its high temp cause melting when plume encounters continental lithosphere and can produce mafic magma at lower parts of lithosphere while upper parts generate felsic magma which can mix and produce intermediate. consequently, erupted magmas can be all types.

Decompression

rock rises into lower pressure regions and is able to melt

A clastic rock with sand-sized particles is called

sandstone

hazards of scoria cones vs basaltic flows

scoria cones- struck and burned by cinders and being struck by blobs of magma and other projectiles such as volcanic bombs. Basaltic flows- volcanic gases such as CO2 hydrogen sulfide and sulfur dioxide can pose a hazard

How do we assess danger posed by volcano

shape, rock type, age and history

Vesicles

small holes, form when gases dissolved in magma accumulate as bubbles. Form under low pressures on or very near surface. Volcanic Ash is broken vesicles

How melting occurs in continental rifts

solid asthenosphere rises beneath the rift and melts via decompression melting mantle derived mafic magma rises into upper mantle and lower crust and creates magma chambers. Heat from mafic magma melts adjacent continental crust producing felsic magma some felsic magma solidifies underground and others is erupted onto surface Diverse because melting in crust is different based on cases of magma heating continental crust, can be hotter than adjacent crust, or losing heat to crust and then solidifying

pluton

solidified magma chamber. irregular- exposed area less than 100 km^2 is a stock irregularly shaped sheetlike pluton- tabular shape, thin or thick sheet can be vertical horizontal or angled batholith- one or more contiguous plutons that include a number of rock types

Composite Volcanoes

steep conical mountains that are common above subduction zones. occur at ocean-ocean or ocean-continent convergent boundaries. (find more information in notes)

The top layer is a redbed, the middle layer is a sandstone, and the bottom layer is a shale. The redbed is younger than the shale. The principle of ______ allows you to determine this

superposition

topographic changes to a volcano before eruption

surface may change shape as magma inflates the mountain called ground deformation. the use of GPA, tiltmeters, and elite radar maps can help determine change in topography.

Why do some convergent boundaries have volcanism

the subducting plate melts when it reaches the asthenosphere

Bowen's reaction series relates to sedimentary rocks because it can be correlated to

the susceptibility of different minerals to weathering at the surface

Mount pelee

the volcano that erupted in 1902, destroying the town of St. Pierre with pyroclastic flow.

How does viscosity effect explosive eruptions?

thicker most viscous will explode, andesitic rhyolitic

What types of rocks do clastic sediments form

took good notes, check notes about texture, types and size tables

All islands along a hot-spot chain remain volcanically active for the lifetime of the mantle plume involved

true

Investigating sources of magma

two different kinds of basalts have different chemistries. mid-ocean ridge basalt is above line because they have high amounts of vanadium compared to oceanic island basalts.

Porphyritic

two stage cooling process, consists of large and small crystals

Why are there so many different products of weathering

type of material such as if it is soluble in water and weak acid commonly weather. Quartz rich are less soluble during weathering. Different parts of material- if material contains multiple types of minerals can weather in different ways. quartz physically weather into sand grains whereas dark, mafic minerals will chemically weather into clay or iron oxides Importance of fracturing- fracturing makes rocks weaker and makes it much easier to weather. It permits water, air, and organisms to invade the rock which causes more chemical and physical weathering.

How is gas measured

various ground and airplane mounted instruments can measure the amount of SO2 coming from a volcano

Alpha decay

unstable atom released a particle that impacts and heats surrounding materials. Ejected particle is equivalent to a helium nucleus. Original atom lost two protons and two neutrons. New element may be stable or may undergo more radioactive decay which generates additional thermal energy.

Cooling history of magma

use temperature vs depth graph

Rock types in scoria

vesicular basalt, nonvesicular basalt, scoria (highly vesicular and contains other fragments explosively ejected from the volcano).

volcanic dome

viscous lava mounds up above and around a vent. They release deadly pyroclastic flows. Can collapse into itself or explode from gas buildup. (more information in notes)

Factors that control viscosity of magma

viscous magma strongly resists flowing. low temp makes magma very viscous, biggest control over viscosity. Composition- abundant silicate chains make felsic magmas very viscous. Abundant crystals cause magma to flow slower.

Tuff

volcanic rock composed of a mix of volcanic ash, pumice, crystals, and rock fragments.

Pumice

volcanic rock containing vesicles. most pumice floats because there are so many vesicles/ Begins as volcanic glass, but over time can convert into microscopic minerals. felsic to intermediate

How sedimentary rocks form through evaporation precipitation or other chemical reactions

water can evaporate in oceans and lakes and substances like salts or carbonate minerals can be left. when the water evaporates other minerals and salts can precipitate as a crust along the bottom or edges of the water body, called evaporite minerals. Water can be heated, cooled, or mixed, which can generate different chemical reactions in minerals. plants or trees can die, get buried and become lithified creating carbon rick rock called coal. Shells and coral can form a variety of rock called limestone which is mostly calcium carbonate

How does water get in subduction zone?

water is released by sediments and minerals in the descending crust, water travels with subducting plate and as sediment layer thickens, it contains trapped seawater and minerals and can eventually reach the subduction zone. Only water trapped in minerals gets deep enough to cause melting.

How crystallization changes composition of magma

when mafic minerals crystallize from a magma, they extract the mafic components such as magnesium iron and calcium and remaining magma contains less elements used to grow mafic minerals and becomes less mafic and more felsic.