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24.1
The Atmosphere
Atmosphere: layers of gases that surrounds the Earth
Oxygen is produced during photosynthesis
Nitrogen, oxygen, water vapor, and other gases
78% Nitrogen, 21% Oxygen
Air Pressure: the force exerted by the weight of a column of air on a surface
As altitude increases, air pressure and density decrease
Barometer: instrument used to measure air pressure
Four layers of the atmosphere
the Troposphere, the stratosphere, the mesosphere, and the thermosphere
Troposphere: the lowest layer of Earth’s atmosphere
: include almost all of the water vapor=formation of clouds
: about 12km in height
: decrease about 6.5 celsius in 1km
Weather: condition of the atmosphere in a particular place and particular time
Stratosphere: extends from an altitude of about 12km to about 50km
: above 20km from the boundary, the temperature increases as the
altitude increase
Ozone Layer: a region of high ozone concentration
: composed of three oxygen atoms
: two oxygen atoms are split at stratosphere=single oxygen atom
collide with oxygen O2=O3
: absorb UV rays and turn the energy into thermal
energy=increase temperature in higher altitude
Mesosphere: begins at 50km to 80km
: temperature decreases as the altitude increases
Thermosphere: outermost atmosphere, 80km to outer space
: temperature increases rapidly=gas molecules absorb
solar radiation=move fast=increase in temperature
Ionosphere: region of charged particles (ions), overlapping the lower thermosphere
: lose election when they absorb high energy wavelength of solar
radiation
: most dense between 80km to 400km
24.2
The Sun and the Seasons
Form of Energy from the Sun=Radiation
Revolution=movement of one body around another
Rotation=spinning of an object on its axis
Highest Latitude→Equator=Polar, Temperate, Tropic
The tilt of the Sun causes different seasons=unevenly distribute energy
Tilt of Earth's=23.5°
Uneven radiant energy=Climates, weather, convention
Equator=sunlight is most intense
Solstice=sun is directly overhead at latitude 23.5° north or south
Northern Hemisphere
Summer Solstice=Northern Hemisphere is tilted toward the
sun=receives more sunlight than the Southern Hemisphere
Winter Solstice=Northern Hemisphere is tilted away from the Sun=receives
less sunlight than the Southern Hemisphere
Equinox=Hemisphere is tilted toward the sun=lengths of daylight and of
darkness are equal
24.3
Solar Energy and Winds
Incoming Solar Energy from the Sun
30%=reflected back into space by clouds, dust in the air, gases, and Earth’s surface
20%=absorbed by clouds and gases
50%=passes through the atmosphere and is absorbed by the surface
Greenhouse Effect=Certain gases (water vapor, carbon dioxide) absorb infrared
radiation→give energy back to Earth’s surface→warming the lower atmosphere
The major form of radiant energy that enters Earth is visible light. The major form that
is reradiated from the Earth to the atmosphere is infrared.
Energy is transferred within the troposphere in three ways=Radiation, convection,
and conduction
Wind=a natural flow of air from high pressure to low pressure
=caused by difference in air pressure
=hot air rises, cooler air replace that region
Local Wind=a wind that blows over a short distance
=caused by the unequal heating of Earth’s surface within a small
region
Sea Breeze=the cooler air over the water flows toward the land
Land Breeze=cooler air over land moves toward water
Energy is transferred within the troposphere by radiation, conduction, and convection
Radiation=heats the land
Conduction=transfers heat from land and water directly to the few meters of air nearest
Earth’s surface
Convection=moves heat through the troposphere
Global Winds=winds that blow over long distances from a specific direction=caused by
unequal heating of Earth
Warm air rises and cold air sinks between specific regions=groups of global winds
that move in a series of huge bands
Coriolis Effect=the apparent deflection of all free moving objects with respect to a
rotating frame of reference
The Coriolis Effect causes a rightward deflection of global winds in the Northern
hemisphere and a leftward deflection of global winds in the Southern hemisphere.
Equator is moving faster than the pole
Monsoon=a wind system that is characterized by seasonal reversal of direction
Jet stream=a belt of high-speed wind in the upper troposphere
24.4
Water in the Atmosphere
-Humidity=the amount of water vapor in the air
-warm, tropical air tends to contain more water vapor than cold,
polar does
-Relative Humidity=the ratio of the amount of water vapor in the air to the maximum
amount of water vapor that can exist at that temperature (expressed as %)
-The maximum amount of water that can exist as a gas is greater at high temperature
than at low temperature
-Dew Point=the temperature at which air becomes saturated
-Water Vapor typically condenses as dew, frost, clouds, or fog
-Cloud=a dense, visible mass of tiny droplets or ice crystals that are suspended in the
atmosphere
-consist billions of droplets and crystals
-form as warm, moist air rises and water vapor condenses in the
atmosphere
-solid particles such as dust and salt must be present for the water vapor to
condense upon
-Fogs=a cloud that is near or touching the ground
-form when warm, moist air passes over land
-form when the ground cools at night, cooling the humid air immediately
above the ground to the dew point
-Three basic clouds forms:Stratus, Cumulus, and Cirrus
-Stratus clouds=falt layers of clouds that cover much or all of the sky
-Stratus=spread out
-Nimbostratus clouds=low stratus clouds that produce steady and widespread rain or
snow
-Nimbo- or -nimbus=cloud produces
precipitation
-Altostratus clouds=middle-level clouds, often form a layer that covers most of the sky
-Alto-=2000~6000 meters
-Cumulus Clouds=puffy white clouds that look like piles of cotton balls with flat
bottoms
-fair-weather clouds
-Cumulus=heap
-Cumulonimbus clouds(thunderheads)=dark, towering clouds that produce heavy
precipitation with thunder and lightening
-Cirrus Clouds=white, wispy clouds, often with a feathery or veil-like appearance
-high in the sky on a clear, sunny day
-Cirro-=high-latitude clouds
-high altitude so mostly ice crystals
-The most common types of precipitation are rain, snow, hail, sleet, and freezing
rain
24.5
Weather Patterns
-Air mass=a large body of air that has fairly uniform physical properties, such as
temperature and moisture content, at any given altitude
-form when a large body of air becomes stationary over Earth’s surface, or
ocean
-influenced by the properties of the region
-Cold=Maritime polar, continental polar
-Warm=Maritime tropical, continental tropical
-Air masses move with the circulation of air
-air masses collide at the middle latitude
-Fronts=sharply defined boundary that forms when two unlike air masses meet
-clouds and precipitation often accompany fronts
-Cold fronts, Warm fronts, Stationary fronts, Occluded fronts
-Cold Fronts=occurs when a cold air mass overtakes a warm air mass
-warm air is lifted rapidly
-cold air is denser and stay near the ground
-cumulus and cumulonimbus clouds form
-strong winds, severe thunderstorms, and large amount of
precipitation
-steep and travel quickly, the weather lasts for only short time,
temperature drops
-Warm Fronts=occurs when a warm air mass overtakes a cold air mass
-less steep than the cold front
-gentle slope because the advancing warm air mass gradually
moves up and over the cold air mass
-stratus clouds form
-warm air mass contains a large amount of moisture, there will
be a steady rain, occasionally heavy showers or thunderstorms occur
-warm air mass settles in, mostly clear, some cumulus clouds,
temperature rises
-Stationary Fronts=neither air masses are moving
-often results in clouds and steady rain or snow for
several days
-Occluded Fronts=when warm air mass is caught between two air masses
-warm air rises, and cools, its water vapor typically
condenses
-cloudy skies and precipitation
-Cyclones=a weather system with a center of low air pressure
-air spirals in toward the center of a cyclone (high to low)
-associated with clouds, precipitation, and stormy weather
-fronts develop
-moves in the direction of global winds, westerly winds
-Anticyclones=a weather system with a swirling center of high air pressure
-clockwise in the Northern Hemisphere
-since the center has high pressure, air flows away from that
center
-as air flows away, air from higher in the troposphere descends
and replaces it=humidity decreases
-clear skies, very little precipitation, and generally calm
conditions
Storms
-Thunderstorm=a small weather system that includes thunder and lightning
-strong winds and heavy rain or hail
-form when columns of air rise within a cumulonimbus
cloud
-cold front forms
-Lightning=sudden electrical discharge in the atmosphere
-Thunder=the sound produced by rapidly expanding air along the path of a lightning
discharge
-Tornado (Twister)=a small but intense windstorm that takes the form of a rotating
column of air that touches the ground
-forms when a vertical cylinder of rotating air develops
in a thunderstorm
-Hurricane=a large tropical cyclone with winds of at least 119km per hour
23.1
Fresh Water
-Only about three percent of Earth’s water is fresh
-Most of Earth’s liquid fresh water is in the form of Groundwater
-Groundwater=the water found underground within cracks and between particles of
rock and soil
-Water Cycle=continuous movement of water
-evaporation, transpiration, condensation, precipitation, and
the eventual return of flowing water to the ocean
-the energy of sunlight and the force of gravity power the
water cycle
-Evaporation=process that changes a liquid into a gas
-warm, moist air expands and rises, carrying the water vapor into
the atmosphere
-Transpiration=water vapor released from trees and other plants
-Condensation=water vapor forms droplets on small particles in the air
-these droplets form clouds
-Precipitation=when droplets get heavy, gravity causes them to fall to the ground (rain,
snow, sleet, hail, or freezing rain)
-Glacier=a large mass of moving ice and snow on land
-A small portion of Earth’s fresh water is located in the atmosphere, streams, and
lakes. Most is located in groundwater and glaciers.
-Runoff=water that flows over Earth’s surface
-Tributaries=collect runoff from the surrounding land and channel it into rivers
-Watershed=the area of land that contributes water to a river system
-Saturated zone=a region where the pore spaces are entirely filled with groundwater
-Water table=the top of the saturated zone
-Permeable (sandstone and limestone)=water can easily pass through it
-Aquifer=a permeable rock layer that is saturated with water
-Impermeable (shale and unbroken granite)=water cannot easily pass through them
23.2
Weathering and Mass Movement
-Erosion=the process that wears down and carries away rock and soil
-destructive process that has shaped Earth’s surface over hundreds of
millions of years
-Acts through watering, the force of gravity, and through the movement
of streams, groundwater, glaciers, wind, and waves
-Weathering=the process by which rocks are chemically altered or physically broken
down into fragments at or near Earth’s surface
-Mechanical and chemical=rocks to disintegrate or decompose
-Mechanical weathering=process of physically breaking rock into smaller fragments
-frost wedging, abrasion, growth of plant
roots, and others
-erode in a long period of time
-Frost Weathering=water freezes to form ice, the water expands
-this expansion open cracks that
water has seeped into
-water freezes at night/melts during
the day
-Abrasion=occurs when rocks scrape or grind against one another
-sand carried by water or wind causes bits of rock
break off
-Plant roots can grow into cracks in a rock
-exert powerful force=slowly pry the rock apart
-release pressure=expand and crack
-Chemical Weathering=process in which rock is broken down by chemical reactions
-chemical reactions that dissolve the minerals
making up rock or change them into new minerals
-rock crumbles
-Water=main source of weathering
-all minerals dissolve in water
-Acid Rain=water a carbon dioxide combine=carbonic acid
-dissolve many minerals
-Rusting of minerals=oxidation
-formation of new minerals=red and brown
-The rate at which mechanical and chemical weathering take place depends on
there main factors=Temperature, the availability of water, and the type of rock
-Chemical Weathering=rapid with high temperatures and abundant rainfall
-Mechanical Weathering=rapid with alternate temperature (freezing and thawing)
-Limestone and marble=rapid chemical weathering
-Calcite=reacts readily with carbonic acid
-Mass Movement=downward movement of rock and soil due to gravity
-gravity moves loose material down a slope
-Landslides=rapid movement of large amounts or rock and soil
-after heavy rains or after earthquakes
-Mudflows=rapid movements of soil and other sediment mixed with water
-Creep=occurs when soil gradually moves down a slope
-formation of ice=expands outward
-thaws=soil moves a small distance downhill
-Slumping=weak layers of soil or rock suddenly move downslope as single
unit
-curved scar
23.3
Water Shapes the Land
-Deposition=the process in which sediment is laid down in new locations
-Erosion begins when runoff carries small particles of soil downhill→Gullies
(channels join together to form large channels)→Streams (flow together)
-Streams transport sediment
-Larger particles=slide, roll, or bounce along bottom of a stream
-Saltation=particles bouncing along a stream bottom
-Faster streams carry more sediment=increase abrasion
-A stream’s ability to erode depends mainly on its speed
-Water erosion forms V-shaped valleys, waterfalls, meanders, and oxbow lakes
-V-shaped Valleys=mass movement on the stream slopes
-rapids and waterfalls
-waterfall develop=rock layers differ in
hardness
-harder layers resist erosion=forming the top
of the waterfall
-softer rock layers downstream are worn
away=leaving the cliff over which the waterfall rumbles
-Flood Plains=the flat area along a stream that is entirely covered only during
times of flood
-river flows across=deposits sediment=builds up into
long, low ridges=natural levees
-Meander=outside of the curve=faster=more erosion
-inside of the curve=slower
-sediment deposit inside
-Oxbow lake=curved lake
-new channel made by flood
-Features deposited by flowing water include alluvial fans and deltas
-Alluvial fan=fan-shped deposit of sediment on land
-grow into thick deposits of sediment
-Delta=a mass of sediment deposited where a river enters a large body of water
(triangular shape)
-The processes of chemical weathering causes much groundwater erosion, including
the formation of caves and sinkholes
-Stalactite=water drips from the cavern ceiling, an icicle-like formation
-Sinkhole=erosion weakens a layer of limestone, entire portions of the ground can
suddenly collapse=hole
23.4
Glaciers and Wind
-Glaciers
-Glaciers form in places where more snow falls than melts or sublimates
-Weight packs the snow tightly=glacier ice is formed
-Constantly moving because of gravity
-Continental glacier=thick sheet of ice that covers a huge area (continent or large
island)
-Valley glacier=glacier that occurs in a high mountain valley
-Erode rock through abrasion and plucking
-Plucking=glacial ice widens cracks in bedrock beneath the glacier
-scrapes the bedrock with sediments
-Glaciers cause many distinctive features in the land scape, including cirques, horns,
U-shaped valleys, and glacial lakes
-Cirques=large bowl-shaped valleys out of a mountainside
-Ridges=several cirques form close, left between them
-Horn=several ridges connect to form a pyramid-shaped peak
-Glaciers widen V-shaped valley=U-shaped valley
-Create lakes
-When a glacier melts, it deposits its load of sediment, creating a variety of
landforms
-Till=glacial sediment
-Moraines=mounds of sediment at the downhill end of the glacier along its
sides
-Wind Erosion and Deposition
-Slower winds carry small particles (dust)
-Faster winds have more energy and can lift larger particles (sand grains)
-Strong winds can produce a large cloud of dust or sand
-Wind erodes the land by deflation and abrasion
-Deflation=wind picks up and carries away loose surface material
-Features deposited by wind include sand dunes and loess deposits
-Dunes=deposits formed from windblown sand
-Loess=consists mainly of finely ground particles
-deserts and glacial deposits
23.5
The Restless Ocean
-Salinity=the proportion of dissolved salts in water
-Light and temperature decrease with depth, whereas pressure increases
-Continental shelf=gently sloping plain forms an apron of shallow water along the
edges of most continents
-descends more steeply to the floor of the deep ocean
-deep canyons cutting though the continental shelf and
slope
-Ocean currents=water flows from one ocean to another
-affected by winds, Earth’s rotation, and the positions
and shapes of continents
-Surface current=large stream of ocean water that moves continuously in about the
same path
-Surface current=a large stream of ocean water that moves continuously in about the
same path
-Winds blowing across the surface of the ocean cause the continuous flow of surface
currents
-Deep ocean currents are caused by differences in the density of ocean water
-colder temperatures or higher salinity=denser water
-Density currents=deep ocean currents are affected by density
-responsible for a slow mixing of water between the surface and deeper ocean
-Upwelling=the movement of water from the deep ocean to the surface
-In upwelling, winds blow warm surface water aside. This allows cold water from
the deep ocean to rise and take the place of the warmer water
-bring nutrients from deep in the ocean to the surface
-Two physical processes, hydraulic action and abrasion, are responsible for much
wave erosion
-Hydraulic action=waves pound on cracks in rocks
-wave fills a crack=pressure increases
-compress air
-abrasion
-Longshore drift=the process that moves sand along a shore
-in a zigzag motion
-Current slow down and deposit sediment=spit
22.1
Earth’s Structure
-Geology is the study of planet Earth, including its composition and structure
-Geologist=study of geology
-Constructive/Destructive Force
-Constructive=shape the surface by building up mountains and other land
areas
-Destructive=slowly wear away mountains and, eventually, every other
feature on Earth’s surface
-Uniformitarianism=the idea that the geologic processes that operate today also
operated in the past
-Earth=the crust, mantle, and core-based on the materials that make up each layer
-layering due to differences in density
-temperature and pressure increase with depth
-Crust=the rocky outer layer of Earth/made out of silicates
-Silicates=rocks made of compounds of silicon and oxygen
-Continental crust/Oceanic crust
-Continental=the rock that makes up the continents, consists mainly of
less-dense rocks such s granite
-40km in thickness (8km to 75km)
-Oceanic=makes up the ocean floor
-mostly of dense rocks like basalt
-about 7km
-Mantle=a thick layer of hot but solid rock
-2850km (beneath the crust to the top of the core)
-rich in iron and magnesium
-Lithosphere=a layer of relatively cool, rigid rock that includes the
uppermost part of the mantle as well as Earth’s crust
-about 100km
-Asthenosphere=a layer of softer, weaker rock that can flow slowly, the way
taffy does
-Mesosphere=stronger lower part of the mantle, beneath the asthenosphere
-stiffer rock extends all to upper surface of Earth’s
core
-Core=a larger sphere of metal that occupies Earth’s center
-mostly of iron, some nickel and lighter elements
-3.6 million times the pressure at surface/5,500°C
-Outer=high temperatures keep the metal liquid
-rotation of Earth=iron produces an electric current=magnetic field
-Inner=high pressure=solid
22.2
Minerals
-Rock=a solid combination of minerals or mineral materials
-a mineral is a naturally occurring, inorganic solid with a crystal structure and a
characteristic chemical composition
-Inorganic=living things did not produce them=minerals
-minerals are building blocks of rocks
-The properties by which minerals can be identified include their crystal structure,
color, streak, luster, density, hardness, fracture, and cleavage
-Common minerals=Appendix D
-A crystal is a solid in which atoms are arranged in a regular repeating pattern
-Crystal structure=atomes are arranged in a particular geometric shape
-size can vary
-Color=some minerals can be identified by color
-Streak=the color of a mineral’s powder
-scraping the mineral on a piece of unglazed porcelain=streak plate
-Luster=the way in which its surface reflects light/how shiny
-rough, crumbly surface=earthy luster
-silky, pearly, and vitreous (glassy)
-Density=chemical composition
-higher atomic masses=higher density
-Hardness=the resistance of a mineral to scratching
-scaled 1 to 10=Mohs hardness scale
-Fracture=how the mineral breaks
-determined by the crystalline structure of the mineral and the bonds
between the atoms in the crystals
-Cleavage=type of fracture in which the mineral tends to split along regular, well
defined planes (flat surfaces) where the bonds are weakest
-Other properties=acid, magnet, electrical properties, refraction
22.3
qRocks and the Rock Cycle
-Rocks are classified into three major groups=Igneous, Sedimentary, and
Metamorphic=based on how they form
-Igneous Rock=a rock that forms from magma
-forms when molten material cools and solidifies either
inside Earth or at the surface
-Intrusive rock=an igneous rock that forms underground from hardened
magma
-rich in iron and magnesium=dark color
-less dense=lighter color
-grow large underground, cool down
slowly/coarse-grained texture
-Extrusive rock=an igneous rock that forms at Earth’s surface
-cool very quickly=small crystals/fine-grained
texture
-Magma=a mixture of molten rock and gases, including water vapor, which
forms underground
-Lava=magma that flows out of volcanoes
-Sediment=consists of small, solid pieces of material that comes from rocks or living
organisms
-Sedimentary rock=a rock that forms over time as sediment is squeezed and cemented
-Clastic rocks, chemical rocks, and organic rocks (how they form)
-Clastic rocks=form from the broken fragments of other rocks
-held together by cement
-Conglomerate=consists of gravel and pebbles
-Breccia=made up of sharp edged fragments
-Mudstone=primarily mud or silt
-Shale=clay minerals are aligned, so it can split into sheets
-Chemical rocks=minerals precipitate out of solution
-Organic rocks=the result of organic processes
-Metamorphic rock=changed by temperature, pressure, or reactions with hot water
-transformed by heat, pressure, or chemical reactions/under high
temperatures and pressure deep underground
-Foliated rocks=metamorphic rocks with crystals arranged in parallel layers or bands
-Rock cycle=series of processes in which rocks continuously change from one type to
another
-forces within Earth and at the surface cause rocks to change form
22.4
Plate Tectonics
-Plate tectonics=the theory that pieces of Earth’s lithosphere, called plates, move about
slowly on top of the asthenosphere
-explains the formation and movement of Earth’s plates
-Alfred Wegener=continents were once joined in a single supercontinent, which
then broke into pieces that moved apart
-Pangaea=supercontinent (all land)
-Continental drift=a process of the continents move slowly across Earth’s surface
-Mid-ocean ridge=a chain of underwater mountains
-Sea-floor spreading=the process by which new oceanic crust is created at mid-ocean
ridges as older crust moves away
-Subduction=old oceanic plates sink into the mantle, as sea-floor spreading occurs
-near the edges of oceanic plates=subduction zone
-Trench=as a plate sinks through a subduction zone, it bends, forming a depression in
the ocean floor
-Sea-floor spreading creates new oceanic crust at mid-ocean ridges. Subduction
destroys old oceanic crust at subduction zones.
-Plate motions are the visible part of the process of mantle convection
-There are three types of plate boundaries: Divergent boundaries, Convergent
boundaries, Transform boundaries
-Move apart, collide, slide past each other
-Divergent boundary=plates move away from each other
-Convergent boundary=plates come together/collide
-Transform boundary=plates slide past each other, moving in opposite directions
-Most mountains form along plate boundaries
22.5
Earthquakes
-Earthquake=a movement of Earth’s lithosphere that occurs when rock in the
lithosphere suddenly shift, releasing stored energy
-Seismic waves=a small portion of the energy released during an earthquake is carried
by vibrations
-Tsunami=a large sea wave generated by an underwater earthquake, volcano, or
landslide
-Stress=a force that squeezes rocks together, stretches or pulls them apart, or pushes
them in different directions
-As tectonic plates move, they cause stress in the crust, which in turn produces
faults and folds
-Fault=a break in a mass of rock along which movement occurs
-Fold=a bend in layers of rock/squeezed together but do not break
-tend to fold rather than break when they are under high temperature or
pressure
-Earthquakes occur because stress forces have exceeded the strength of rock
-Focus=the location beneath Earth’s surface where an earthquake begin
-Epicenter=the location on Earth’s surface directly above the focus
-Potential energy→Kinetic energy (form of seismic waves)
-Earthquakes produce three main types of seismic waves:P waves,, S waves, and
Surface waves
-P waves (primary waves)=longitudinal waves similar to sound waves
-cause particles in the material to
liberate in the direction of the waves’ motion=solids and liquids
-compress and expand the ground
-fastest seismic waves=first to be
detected
-S waves (secondary waves)=transverse waves
-cause the particles in the particles
in the materials to vibrate at right angles to the direction the waves move
-only solids
-Surface waves=waves that develop when seismic waves reach Earth’s surface
-slower but produce larger ground movements and greater
damage
-To measure earthquakes and pinpoint their epicenters, geologists record seismic
waves using seismographs
-Seismographs=a device that can detect and record seismic waves
-Seismogram=the record of an earthquake on a seismograph
-Richter Scale=the most well-known scale
-rates based on measurements of the times and amplitudes of
seismic waves
-Moment Magnitude Scale=the most useful scale for geologists
-a measure of the amount of energy released
by an earthquake
-32-times increase in the energy release for
each unit
-Modified Mercalli Scale=ranges from 1 to 12, based on observations of the intensity of
ground shaking and damage in the areas affected by an earthquake
-Most earthquakes are concentrated along plate boundaries, where many faults are
found
22.6
Volcanoes
-Volcano=a mountain that forms when magma reaches the surface
-Under certain conditions, small amounts of mantle rock can melt, forming liquid
magma. The magma rises upward through the crust, erupting at the surface as a
volcano
-less dense
-Magma chamber=a pocket where magma is collected
-Pipe=narrow, vertical channel where magma rises
-Vent=an opening in the ground where escapes to the surface
-Crater=bow-shaped pit at the top of the central vent in most volcanoes
-Caldera=a huge depression created by the empty chamber (hollow shell) collapsing
inward
-Volcanoes erupt explosively or quietly, depending on the characteristics of the
magma
-Viscosity=the resistance to flow
-High viscosity=thick and resists easily
-Low viscosity=thin and flows easily
-Temperatures, water content, silica content=determine the viscosity of magma
-Higher temperature=lower viscosity
-Water=flow more easily
-High in silica=high viscosity
-Quiet Eruptions=very hot, low-silica magma=erupt quietly
-travel for great distances
-Two lavas=pahoehoe,aa
-Pahoehoe=hot, fast-moving lava with a replica surface
-Aa=cooler, slow-moving lava with a chunky, crumbly appearance
-Explosive Eruptions=high-silica magma
-clog the pipe=increase in pressure
-solidifies very quickly and shatters into pieces
of different sizes
-Most volcanoes occur along plate boundaries or at hot spots in the crust
-Ring of Fire=the trenches at the rim of Pacific ocean
-Hot spot=a region where hot rock extends from deep within the mantle to the surface
-The three major types of volcano are shield volcanoes, cinder cones, composite
volcanoes
-Shield volcano=wide, flat volcano produced by a quiet eruption
-Cinder cone=small, steep-sided volcano produced by an eruption of ash and
cinders
-Composite volcano=formed from explosive eruptions that produce a
combination of lava and ash
-Igneous features formed by magma include batholiths, sills, dikes, and volcanic
necks
-Batholith=the largest type of intrusive igneous rock mass
-Magma squeezes into a crack between layers if rock and then hardens. If the crack is
parallel to existing rock layers, the magma hardens into a structure called a Sill.
-If the crack cuts across rock layers, the hardened magma forms a Dike.
-Volcanic neck=the magma hardened in a volcanic pipe
-Lava plateau=layers of hardened lava may form a high, level area