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Earth Science-Digital Notebook

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Samantha St. Andre

on 20 December 2012

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Transcript of Earth Science-Digital Notebook

Ellie Raulston Earth & Space Science photo credit Nasa / Goddard Space Flight Center / Reto Stöckli CHAPTER ONE Section 1.1 Earth science deals with Earth and its neighbors in space. geology-study of Earth
oceanography-study of oceans
meteorology-study of atmosphere/weather
astronomy-study of universe The universe started with the big bang The big bang sent out H, He, Br, Li Section 1.2 Cloud of dust transformed into Earth. began with cloud of dust (molecular clouds) ball began to spin&heat up to become the sun cloud spread out and began forming Earth the materials began sticking together due to zero gravity clumps of particles gather material from other areas the 20 planets' orbits caused them to collide leaving us with less planets hydrosphere- ball of water
atmosphere- ball of air
geosphere- ball of rock
biosphere- ball of life 3 Main Parts of Earth's Surface core
mantle
crust Section 2.1 CHAPTER TWO solid- definite shape & volume
liquid- definite volume
gas- neither proton- defines the element (+ charge)
electron- (- charge)
neutron- (neutral charge) Electrons and neutrons can change and still have the same element. If the number of protons change, you end up with a different element. Protons (+) & electrons (-) attract each other. Section 2.2 How do minerals form? Mineral crystals form when water evaporates leaving behind minerals that were dissolved. Molten rock cools and crystallizes. Crystallization of Melted Minerals the magma cools faster when closer to the surface Crystallization of Minerals Dissolved in Water hot water solutions in the Earth cool&form minerals evaporating water can leave behind crystals Types of Minerals Silicates
contain mixture of oxygen and silicon Nonsilicates
NOT formed from oxygen and silicon Section 1.3 latitude --
longitude | Types of Maps Topographic Map Geologic Map Conic Map Gnomonic Map Section 1.4 Earth is a system A system can be any size group of interacting parts that form a complex whole. The earth system is powered by energy from two sources. 1. The sun
-drives external processes that occur in the atmosphere, hydrosphere, and at Earth's surface. 2. Earth's interior Our actions produce changes in all of the other parts of the Earth system. Renewable resources can be replenished over relatively short time spans. Although these and other resources continue to form, the processes that create them are so slow that it takes millions of years for significant deposits to accumulate. Significant threats to the environment include air pollution, acid rain, ozone depletion, and global warming. A mineral is a naturally occurring , inorganic solid with an orderly crystalline structure and a definite chemical composition. There are four major processes by which minerals form: 1. Crystallization from magma.
-As magma cools, elements combine to form minerals. 2. Precipitation
-Water contains many dissolved substances. When this water evaporates, some of the dissolved substances can react to form minerals. 3. Pressure and temperature
-An increase in pressure can cause a mineral to recrystallize. Changes in temperature can also cause certain minerals to become unstable. 4. Hydrothermal solutions
-A solution of very hot mixture of water and dissolved substances. When these solution come into contact with existing minerals, chemical reactions take place to form new minerals. Minerals are classified by composition. Mineral Groups Silicates (most abundant)
-silicon & oxygen combine to form a silicon-oxygen tetrahedron
Example- Quartz Carbonates (2nd most abundant)
-contain carbon, oxygen, & 1+ metallic element
Example- Calcite Oxides
-contain oxygen & 1+ elements (usually metals)
Example- Rutile Sulfates & Sulfides
-contain sulfur
Example- Gypsum
-sulfate
-forms when mineral-rich waters evaporate
Example- Pyrite
-sulfide
-forms from thermal (hot-water) solutions Halides
-contain halogen ion & 1+ element
Example- Fluorine Native Elements
-contain one element or type of atom
Example- Gold Section 2.3 Properties of Minerals Color
-not often useful in identifying minerals
-small amounts of different elements can give the same mineral different colors. Streak
-the color a mineral is in powdered form
-no matter the color of one type of mineral, the streak usually does not vary Luster
-describes how light is reflected from the surface of a mineral
-Examples; metallic luster, nonmetallic luster (vitreous, glassy), sub-metallic luster, (pearly, silky, earthy) Crystal Form
-the visible expression of a mineral's internal arrangement of atoms Hardness
-measure of the resistance of a mineral to being scratched
-Mohs hardness scale consists of 10 minerals arranged from 10 (hardest) to 1 (softest)
-diamond is the hardest mineral on Earth Cleavage
-the tendency of a mineral to cleave, or break, along flat, even surfaces Fracture
-minerals that do not show cleavage
-the uneven breakage of a mineral Density
-the property of all matter that is the ratio of an object's mass to its volume
-Density (D) = mass (m)/Volume (V) Distinctive Properties of Minerals
-some minerals can be recognized by other distinctive properties
-Examples; talc and graphite have distinctive feels, gold and silver are easily shaped
-hydrochloric acid causes carbonate minerals to fizz CHAPTER THREE Section 3.1 A rock is any solid mass of mineral or mineral-like matter that occurs naturally as part of our planet. THREE MAJOR TYPES OF ROCK
-igneous
-sedimentary
-metamorphic Rocks Minerals Intro to Earth Science Interactions among Earth's water, air and land can cause rocks to change from one type to another. When magma cools and hardens beneath the surface or as a result of a volcanic eruption, igneous rock forms. Weathering: a process in which rocks are physically and chemically broken down by water, air, and living things to produce sediment. Sediment is made up of weathered pieces of earth materials. Eventually, sediment is compacted and cemented to form sedimentary rock. Under extreme pressure and temperature conditions, sedimentary rock will change into metamorphic rock. If metamorphic rocks are subjected to higher temperatures or additional pressure changes, they will melt into magma and form igneous rock again. Processes driven by heat from Earth's interior are responsible for forming igneous and metamorphic rocks. Weathering and the movement of weathered materials are external processes powered by the energy from the sun and by gravity. Processes on and near Earth's surface produce sedimentary rocks. Section 5.2 -form when magma hardens beneath Earth's surface -form when lava hardens -minerals grow in size as the magma cools which forms a solid mass of interlocking crystals -example; granite -lava is similar to magma, except that most of the gases have escaped -example; rhyolite Classification of Igneous Rocks Texture and composition are two characteristics used to classify igneous rocks Course-Grained Texture
-slow cooling results in the formation of large crystals
-example; granite (intrusive) Fine-Grained Texture
-rapid cooling of magma or lava results in rocks with small, interconnected mineral grains
-example; basalt (extrusive) Glassy Texture
-when lava spews out of the Earth's surface
-not enough time for the ions to arrange themselves into a network of crystals
-example; obsidian (extrusive) Porphyritic Texture
-a large body of magma under the Earth's surface that can take thousands of years to harden
-minerals do no form at the same rate or at the same time
-example; andesite (intrusive) TEXTURE COMPOSITION Granitic Composition
-light-colored silicate minerals quartz and feldspar are the main minerals
-contain about 10% dark silicate minerals; 70% silica
-example; rhyolite & quartz Basaltic Composition
-dark silicate minerals and plagioclase feldspar
-rich in magnesium and iron
-typically darker and denser than granitic rocks
-example; basalt Other Compositional Groups Andesitic Composition
-composition between granitic and basaltic
-25% dark silicate minerals and plagioclase feldspar Peridotite
-contains mostly olivine and pyroxene
-ultramafic: composed of almost entirely dark silicate minerals. Rare at Earth's surface Section 3.3 Formation of Sedimentary Rocks 1. Weathering
-often the first step
-chemical weathering takes place when the minerals in rocks change into new substances
-when physical forces break rocks into smaller pieces
-living things can cause chemical & physical weather 2. Erosion
-involves weathering and the removal of rock 3. Deposition
-when water, ice, wind, or gravity loses energy, it drops the sediments
-sediments deposited according to size
-largest sediments deposited first; smaller sediments deposited later 4. Compaction & Cementation
-change sediments into sedimentary rocks
-compaction: the process that squeezes (compacts) sediments
-caused by the weight of sediments
-cementation: when dissolved minerals are deposited into tiny spaces among the sediments Classification of Sedimentary Rocks Sedimentary rocks can be classified into two main groups Clastic Chemical Includes rocks that are made of weathered bits of rocks and minerals Forms when dissolved minerals precipitate from water solutions Many different minerals can be found in clastic rocks Can be grouped according to the size of the sediments in the rock EXAMPLES Conglomerate: rounded, gravel-size or larger particles Breccia: angular particles Sandstone: sand-sized grains Shale: very fine-grained, most common Siltstone: fine-grained Generally occurs when water evaporates or boils off leaving a solid product. EXAMPLES Limestone Rock salt Chert Flint Rock gypsum Some limestones are formed from biochemical sediments. Such sediments are the shells and skeletal remains of organisms that settle to the ocean floor. Example; coquina The many unique features of sedimentary rocks are clues to how, when, and where the rocks formed. The oldest layers are found on the bottom; the youngest layers are on top Ripple marks may indicate that the rock formed along a beach or stream bed Fossils are unique to some sedimentary rocks because they can be used to help answer questions about the rocks that contain them. Examples; DId the rock form in the ocean or on land? Was the climate hot or cold? Rainy or dry? Section 3.4 Metamorphism means to change form Most metamorphic changes occur at elevated temperatures and pressures. These conditions are found a few kilometers below Earth's surface and extend into the upper mantle. Occurs in one of two settings;
1. Contact metamorphism
-when magma intrudes rock
-often produces what is described as low-grade metamorphism
-changes in rock are minor
-EXAMPLE; marble
2. Regional metamorphism
-when large areas of rocks are subjected to extreme pressures and temperatures
-occurs during mountain building
-results in large-scale deformation and high-grade metamorphism 1. Heat
-most important
-provides the energy needed for chemical reactions
-causes new minerals to form
-comes from mainly two sources (magma & the change in temperature with depth) There are three agents of metamorphism; 2. Pressure
-increases with depth
-applied in all directions
-causes the spaces between mineral grains to form
-may causes minerals to recrystallize into new minerals 3. Reactions in solution
-water solutions containing other substances that readily change to gases at the surface play an important role in metamorphism
-solutions that surround a mineral grain aid in recrystallization
-hydrothemal solutions: hot, water-based solutions that escape from a mass of magma
-promote recrystallization by dissolving original minerals and depositing new ones Classification of Metamorphic Rocks Foliated
-become compact and dense due to contact metamorphism
-pressure causes the minerals to align in a similar direction
-some minerals will recrystallize into a preferrede orientation at right angles to the direction of the force
-EXAMPLE; gneiss Nonfoliated
-does not have a banded texture
-contain one mineral
-EXAMPLE; marble Meta = change
Morphic = form Characeristics of Metamorphic Rocks
-classified by texture & composition
-rarely have fossils
-may react with acid
-may have alternate bands of light and dark colored minerals
-rarely has pores & openings
-may be composed of one mineral
-may have layers of visible crystals
-may have a bent or curved formation
-usually made of mineral crystals of different sizes EXAMPLES;
sandstone becomes quartzite
-light-colored & unfoliated
shale becomes slate
-dark & foliated
limestone becomes marble
-light-colored and unfoliated
gneiss
-pink/gray & foliated Sedimentum = Settling Weathering, Soil, and Mass Movements Chapter 5 Mechanical Section 5.1 There are two types of weathering: Occurs when physical forces break rock into smaller and smaller pieces without changing the rock's mineral composition. Three Physical Processes Important Causes of Mechanical Weathering 1. Frost Wedging: When liquid water freezes and expands making the cracks. Sections of rock that are wedged loose may tumble into large piles called talus. 2. Uploading: Large masses of igneous rock exposed through uplift and erosion. Slabs of the outer rock seperate; this is called exfoliation. 3. Biological Activity: The activities of organisms, including plants, burrowing animals, and humans.
-Plants: Grow into cracks in rocks
-Animals: Moves rocks to the surface
-Humans: Deforestation, searching for minerals, and creating new roads Chemical Transformation of rock into one ore more new compounds Agents of Chemical Weathering Water
-most important agent
-absorbs gases from the atmosphere and the ground
-absorbs carbon dioxide when rain falls
-carbon dioxide dissolved in water forms carbonic acid
-also absorbs sulfur oxides and nitrogen oxides
-pollutants are converted into acid rain and accelerate the chemical weathering process Chemical Weathering of Granite
-granite contains mostly feldspar and quartz
-when exposed to water containing carbonic acid, the feldspar is converted to mostly clay minerals; quartz remains unchanged Chemical Weathering of Silicate Minerals
-make up Earth's crust; composed of eight elements
-sodium, calcium, potassium, & magnesium are carried away by groundwater
-iron reacts with oxygen=iron oxide
-aluminum, silicon, & oxygen combine with water and produce clay minerals Spheroidal Weathering
-changes the physical shape of a rock
-water enters along the joints and weathers the corners and edges; become rounded Two other factors that affect the rate of weathering are rock characteristics and climate Rock Characteristics Influence the ability of water to penetrate rock Affects rate of weathering Climate Control the frequency of freeze-thaw cycles Affect the rate of chemical weathering Influence he kind of vegetation and how much is present Climate most favorable for chemical weathering is warm and wet Differential Weathering Different parts of a rock mass often weather at different rates Section 3.2 Weathering produces a layer of a layer of rock regolith
-soil is the part of the regolith that supports the growth of plants *most important factors are parent material, time, climate, organisms, and slope* Parent Material
-source of the mineral matter in soil
-may be either bedrock (residual soil) or unconsolidated deposits (transported soil)
-affects rate of weathering & soil formation
affects soil's fertility Time
-longer the soil forms, thicker it is Climate
-greatest affect on soil
-hot, wet climate = thick, chemically weathered soil
-cold, dry climate = thin, mechanically weathered soil Organisms
-plants are the main source of organic matter
-burrowing animals mix the minerals and organic matter
-bacteria aids in fertility Slope
-steep slopes = accelerated erosion
-holds too little moisture for vigorous plant growth
-thin or nonexistent soil
-direction of slope affects soil formation A HORIZON
-topsoil
-consists of organic matter B HORIZON
-subsoil
-contains fine clay particles C HORIZON
-parent material Glaciers
-found in much of the eastern half of the U.S.
-contains iron oxide & aluminum-rich clays Streams
-found in the drier western U.S.
-contain calcium carbonate Deserts
-found in hot, wet tropical areas
-contains iron & aluminum oxide Water
-rain strikes the soil and carries away particles of soil Human activities that remove natural vegetation, such as farming, logging, and construction, have greatly accelerated erosion Section 5.3 The transfer of rock and soil downslope due to gravity is called mass movement Triggers of Mass Movements Water - heavy rains, rapid melting of snow Oversteepened Slopes - can result when a stream undercuts a valley wall, waves pound against the base of a cliff, and construction Removal of Vegetation - plants make slopes more stable Earthquakes - dislodges large amounts of rock and material Types of Mass Movements rockfalls - when rock falls freely through the air slides - block of material moves suddenly along a flat, inclined surface slumps - downward movement of block material along a curved surface mudflows - flows that move quickly
earthflows - move relatively slow creep - slowest type of mass movement Section 6.1 Chapter 6 The Water Cycle Water constantly moves among the oceans, atmosphere, Earth, and the biosphere. Infiltration- the movement of surface water into rock or soil through cracks and pore spaces Transpiration- when plants absorb water and release it into the atmosphere Earth's Water Balance Balance in the water cycle means the average annual precipitation over Earth equals the amount of water that evaporates Streamflow The ability of a stream to erode and transport materials depends largely on its velocity Gradient- the slope or steepness of a stream channel
-varies over a stream's lenghth and beneath streams Channel Characteristics
-stream channel- the course the water in a stream
-friction slows its forward movement Discharge- the volume of water flowing past a certain point in a given unit of time
-changes with rainfall and snowmelt Changes of Upstream to Downstream When gradient decreases between a stream's headwaters and mouth, discharge increases. Tributary: a stream that empties into another stream Base Level the lowest point to which a stream can erode it's channel A stream in a broad, flat-bottomed valley that is near its base level often develops a course with many bends called meanders. Section 6.2 Erosion
-streams erode their channels by abrasion, grinding, and by dissolving soluble material. Sediment Transport
1. in solution (dissolved load)
2. in suspension (suspended load)
3.scooting or rollling along the bottom (bed load) Dissolved Load:
-enters through groundwater/dissolving rock along stream's course Suspended Load:
-most streams carry their load in suspension Bed Load:
-the part of a stream's load that is made of sediment too large to be carried in suspension Competence & Capacity:
-competence: measures the largest particles it can transport -increases with velocity
-capacity: the maximum load it can carry -directly related to discharge Deposition
-occurs as streamflow drops below the critical settling velocity of a certain particle size.
-alluvium: the sorted material deposited by a stream Deltas:
-an accumulation of sediment formed where a stream enters a lake or ocean

Natural Levees:
-a ridge made up mostly of coarse sediments that parallels some streams Stream Valleys Narrow Valleys:
-V-shaped valley
-shows that the stream's primary work has been downcutting toward base level
-rapids and waterfalls are most prominent Wide Valleys
-streams that flow on floodplains move in meanders & grows larger
-erosion is more effective on the downstream side of a meander Floods and Flood Control Most floods are caused by rapid spring snow melt or storms that bring heavy rains over a large region. A flood occurs when the disharge of a stream becomes so great that it exceeds that capacity of its channel and overflows its banks. Artificial Levees: earthen mounds built on the banks of a river
- increases the volume of water a channel can hold Flood-Control Dam: store floodwater and then let it out slowly
- dams have consequences Limiting Development: minimize development on floodplains allows them to absorb floodwater with little harm to homes and businesses Drainage Basins
-the land area that contributes water to a stream divide: an imaginary line that seperates the drainage basins of one stream from another Section 6.3 Some water sinks into the ground. Much of the water seeps down until it reaches the zone of saturation. The water within this zone is known as groundwater. The upper limit of the zone of saturation is the water table. The amount of ground water that can be stored depends on porosity. Porosity is the percentage of the total volume of rock or sediment that consists of pore spaces. The permeability of a material is its ability to release a fluid Groundwater moves by twisting and turning through interconnected small openings. The groundwater moves more slowly when the pore spaces are smaller. Permeable rock layers or sediments that transmit groundwater freely are aquifers. A spring forms whenever the water table intersects the groundwater. A spring is a flow of groundwater that emerges naturally at the groud surface. A hot spring is 6-9 degrees warmer than the mean annual air temperature where the spring occurs. A geyser is an intermittent hot spring or fountain in which a column of water shoots up with great force at various intervals. A well is a hole bored into the zone of saturation. An artesian well is when the groundwater rises on its own under pressure. Environmental Problems Associated With Groundwater -Treating Groundwater as a Nonrenewable Resource -Groundwater Contamination Cavern
-a naturally formed underground chamber
-erosion forms most caverns at or below the water table in the zone of saturation Stalagmites are formations that develop on the floor of a cavern and reach up toward the ceiling. Karst Topography Landscapes that have been shaped largely by the dissolving power of groundwater. Karst areas typically have irregular terrain, with many depressions called sinkholes.
- a sinkhole is a depression produced in a region where groundwater has removed soluble rock Chapter 7 Section 7.1 ice age: period of time when Earth was covered in glaciers glacier: a thick ice mass that moves slowly over the land surface snowline: the lowest elevation in a particular area that remains covered in snow all year Valley glaciers
-ice masses that slowly advance down valleys that were originally occupied by streams
-a stream of ice that flows between steep walls from a place near the top of the mountain valley Ice sheets
-enormous ice masses that flow in all directions
-sometimes called continental ice sheets becasue they cover large regions where the climate is extremely cold The movement of glaciers is referred to as flow. Glacial flow happens in two ways: plastic flow and basal slip. Different glaciers move at different speeds. The glacial budget is the balance or lack between accumulation at the upper end of a glacier and loss (wastage) at the lower end. Many landscapes were changed by the widespread glaciers of the recenet ice age. 2 Ways Glaciers Erode Land:
1. Plucking
-when water from a glacier breaks up the rock under the glacier, refreezes, and pries the rock apart.
2. Abrasion
-when the glacier slides over the rock under it and polishes it. Glaciers are responsible for a variety of landscape features such as glacial troughs, cirques, aretes, and horns. Cirque: a bowl-shaped depression at the head of a glacier Arete: snaking, sharp-edged ridges Horn: sharp pyramid-like peak 2 Types of Glacial Drift 1. till: material deposited directly by the glacier
2. stratefied drift: sediment layed down by glacial meltwater When glaciers melt, they leave layers or ridges of till called moraine. Lateral Moraines
-ridges that form along the sides of glacial valleys when the glacier melts and leaves the material it has gathered. End Moraines
-ridges made from debris that have been moved to the end of the glacier Ground Moraines
-form when glaciers begin to recede
-forms a gently rolling plain instead of a ridge Terminal Moraine
-the farthest end moraine Recessional Moraine
-the end moraines that form when the ice front occasionally becomes stationary during its retreat Outwash Plains
-a ramp-like accumulation made by streams filled with fine sediment Kettles
-depressions and small lakes within end moraines and outwash plains Drumlins
-streamlined hills composed of till Eskers
-snake-like ridges composed of sand and gravel that were deposited by streams once flowing in tunnels beneath glaciers Section 7.2 Much of the weather debris in deserts have resulted from mechanical weathering. Chemical weathering, however, is possible. Over long time spans, clays and thin soils do form. Most streams in the desert are ephemeral-- they only carry water after it rains. Alluvial fan: a cone of debris left when runoff quickly loses velocity and most of its load is dumped within a short distance Playa lake: formed when streams flow into the center of a basin Most desert erosion results from running water. Section 7.3 Wind erodes in the desert in two ways: deflation and abrasion. Deflation: is the lifting and removal of loose particles Deflation creates a stony surface layer called desert pavement when it removes all the sand and leaves only coarser particles . Abrasion: happens when windblown sand cuts and polishes exposed rock surfaces Wind Deposits Loess: windblown silt that blankets the landscape Sand dunes: blanket-like layers over broad areas deposited by wind in mounds or ridges Types of Sand Dunes Barchan Dunes: solitary sand dunes shaped like crescents
Transverse Dunes: dunes with ridges perpendicular to the wind; typical in coastal areas
Barchanoid Dunes: scalloped rows of sand formed ar right angles to the wind
Longitudinal Dunes: long ridges of sand that form parallel to the prevailing wind
Parabolic Dunes: look like backwards barchans; tips point into the wind instead of away from it
Star Dunes: isolated hills of sand; bases resemble stars; develop in areas of variable wind direction Chapter 8 Section 8.1 An earthquake is the vibration of Earth produced by the rapid release of energy within the lithosphere Fault: fractures in the Earth where movement has occcured Focus: the point within Earth where an earthquake starts Seismic waves: energy released in all directions from the focus of an earthquake Epicenter: the location on the surface directly above the focus Most earthquakes are produced by the rapid release of energy stored in rock that has been subjected to great forces. Elastic rebound: the tendency for the deformed rock along a fault to spring back after an earthquake Aftershock: an earthquake that occurs soon after a major earthquake. Foreshock: small earthquakes that come before a major earthquake. Section 8.2 Earthquakes produce two main types of seismic waves-- body waves and surface waves Body waves;
P Waves- waves that compress and expand particles in the direction that waves travel
S Waves- shake particles at right angles to the waves' direction of travel Surface waves;
-when body waves reach the surface
-travel more slowly than body waves seismogram: instrument used to record seismic waves The Richter scale and the moment magnitude scale measure earthquake magnitude. The Modified Mercalli scale is used to measure an earthquake's intensity. A travel-time graph, data from seismograms made at three or more locations, and a globe can be used to determine an earthquake's epicenter. Section 8.3 Causes of Earthquake Damage
-Earthquake-related hazards include seismic shaking, liquefication, landslides and mudflows, and tsunamis.
1. Seismic Shaking
-jolt and twist structures; buildings may collapse
-strongest closest to an epicenter
2. Liquefication
-when stable soil suddenly turns to liquid
-buildings and bridges may settle and collapse
3. Landslides & Mudflows
-landslides; earthquakes can cause loose rock and soil on slopes to move
-mudflow; when the water content of soil is high and a mixture of soil and water slides rapidly downhill
4. Tsunamis
-a wave formed when the ocean floor shifts during an earthquake
-occurs when an earthquake pushes a slab of ocean floor along a fault Reducing Earthquake Damage
-Damage and loss of life can be reduced by determing earthquake
risk for an area, building earthquake resistant structures, and following earthquake safety precautions.
1. Assessing Earthquake Risk
-most frequent along plate boundaries
-seismic gap: an area along a fault where there has not been any earthquake activity for a long period of time
2. Earthquake Resistant Structures
-cities in earthquake-prone regions have building codes that set standards for earthquake-resistant structures
3. Earthquake Safety Precautions
-drop, cover, and hold Section 8.4 Earth's interior is made up of 3 layers
1. Crust
-thin, rocky outer layer
2. Mantle
-solid, rocky shell around the core
-boundary between crust and mantle represents a change in chemical composition
3. Core
-sphere composed of mainly iron-nickel alloy Layers based on physical properties:
1. Lithosphere
-Earth's outermost layer
2. Athenosphere
-weak; near its melting point
-part of the upper mantle
3. Inner and Outer Core
-outer core; liquid layer
-inner core; compressed into a solid state Studies of the paths of P and S waves through Earth helped scientists determine that the outer core is liquid. Moho: the shorterned name of the boundary that seperates the crust from the underlying mantle To determine the composition of Earth's layers, scientists studied seismic data, rock samples from the crust and mantle, meteorites, and high-pressure experiments on Earth materials.
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