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Science Period 3
Transcript of Science Period 3
period 3 Science Notebook Section 1
What is Earth
the study of stuff that has
to do with the oceans and
salt water Vocabulary Geology
means earth science
historical and physical Meteorology
the study of the
The study of the
Universe Plate Tectonics The Lithosphere is broken into sections that
we call Plate Tectonics. These plates are what
make up our continents, oceans, and other things.
They are also the cause for valcanoes and earth-
quakes. Part ot that theory is that the unequal distrobution of the heat in the Earth's crust causes these plates to move and collide. The collisions cause earthquakes, while the gaps leave open spots were at lava comes through, and these into volcanoes, mountains, and islands. Atoms
Section 2 They are made from electrons,
protons, and neutrons. They also
Have a nucleus at the center.
They cannot be broken down to
smaller sections and still have the
form and charecteristics of an element. You can fit about 1000000000
(1 million) atoms across a piece of
human hair. Section 2.1 Section 2.2 The Periodic Table is the best way to organize elements. They are organized them by the number of protons. Minerals are formed by crystallizing magma, precipitation, changes in pressure and temperature, and hydrothermal solutions. They occur naturally, form inorganic solids with orderly crystalline structure and a definite chemical composition. There are 6 mineral groups, all with different properties and compositions. Different crystals form at different tempartures. Silicates: silicon and oxygen combined.
This forms a tetrahedron which is basis
for all silicates. (4 oxygen and 1 silicon Native elements: a mineral consisting of only one type of element or atom. Halides are minerals with one halogen ion plus one or more other elements. Sulfates and sulides conatain sulfur. Carbonates contain carbon, oxygen, and one or more metallic elements.
Oxides are minerals with oxygen and one or more other elements, usually metals. Properties of Minerals
2.3 Rock composition is made up of color, streaks, luster, crystal forms, hardness, cleavage, fracture, density, other dinstinctive properties. Color: different amounts of elements can give you different colors. Streak: the color of a mineral in a powdered form. Luster: describes how light is reflected of the surface of the mineral, such as: it has a metallic luster. Crystal form: the visible expression of a mineral's internal arrangement of atoms. this is based off of one of six different crystal systems. Hardness: the measure of the resistance of the mineral to being scratched. Tdhe Mohs scale consists of 10 minerals arranged from 10 (hardest) to 1 (softest). Cleavage: the tendency of a mineral
to cleave, or break, along flat, even surfaces. Fracture: MInerals that don't cleave fracture, or break along uneven surfaces. Density: the property of all matter that is the ratio of the object's volume.
D= mass(m)/volume(v) Distinctive properties of Minerals: some minerals can be recognized by distinctive properties, such as texture, magnetism, and double refraction. Chapter 3: Rocks Inter actions between Earth's water, air, and land change rocks and form the rock cycle. Section 3.1: The Rock Cycle Igneous rocks.are made of magma (or lava )that has cooled. Section 3.2
Igneous Rocks Any solid mass of mineral or mineral-like matter that occurs naturally is a rock. Magma cooling is one way that rock form, creating igneous rocks. when magma reaches the surface, it becomes magma. Sedimetary, igneous, and metamorphic are the 3 main types of rocks. Weathering causes rocks to break into sediments, and the these sediments form into sedimentary rocks. Extreme heat and pressure form metamorphic rocks. When an Igneous rock cools slowly, it has a course texture.
When it cools slowly, it gets a glassy texture, like obsidian If the magma cools beneath the surface of the earth, it is called an intrusive rock. if it cools above the surface, it is extrusive. some examples of igneous rock are obsidian, granite, and pumice. Metamorphic rocks are formed
from heat and pressure (and time). Metamorphic Rocks 3.4 Sedimentary Rocks 3.3 Sedimentary rocks are formed from sediments that have been broken off of other rocks and then get glued back together to form different rocks. When wind, water, ice, and gravity break down a rock, it is called physical weathering.
When a rock is broken down chemically and the type of rock is changed, it is called chemical weathering. This also includes rust and the dissolving of rocks + minerals. After being broken off from rocks, sediments are then deposited. They now can become lithified, or turned into rocks. This can happen through compaction and cementation.
Compaction is when the sediments are squeezed, or compacted, so tightly that they stay formed together like that.
Cementation is when dissolved minerals dissolved minerals are deposited in the tiny spaces among the sediments. Heat causes the rocks to "bake." It melts the preciously formed crystals, and allows new ones to form.
Pressure, like heat, changes with the depth. It is also applied from all directions. because of pressure, these rocks seem to elongate and flatten.
Hydrothermal solutions replace the minerals inside the existing rocks, and help to quicken the chemical processes. Metamorphic rocks often looked similar to sedimentary in the fact that they have layers, but half of the layer will be blended, or mixed, together. Metamorphic rocks are made from two main processes. Contact and regional.
Contact metamorphism is where magma forces its way into the rock. This causes minor changes in the rock.
Regional metamorphism is involved in mountain building, and causes more major changes in the rock. Can only be formed by one type of mineral Alternates between light and dark bands of color Chapter 5
Weathering, Soil, and
Mass Movements 5.1 Weathering Soil is part of the regolith that supports plant life. 5.2 Soil Mass movements are the transfer of rock and soil downslope
due to gravty. 5.3 Mass Movements Mechanical Weathering Chemical Weathering Mechanical Weathering is the process of a rock being broken down physically
It is also called physical weathering
There are three main forms of mechanical weathering: frost wedging, unloading, and biological activity
Frost wedging is when water gets between cracks , freezes and thaws repeatedly, breaking the rocks apart over a period of time. Talus are large piles of rocks that have been broken away from larger rocks and generally form at the base of steep cliffs
Unloading: when large masses of igneous rocks are exposed because the covering layers have eroded away, the pressure on the rocks is reduced. This allows the outer layer of rock to spread more. Exfoliation is when slabs of the outer rock are peeled and separated from the lack of pressure.
Biological activity is when organisms, such as plants and animals, break and wear down the rock so it breaks. Also, decaying organisms release acids that help cause chemical weathering. Humans help with this process with activities such as defrosting and blasting to make and improve roads, buildings, and other such structures. Chemical weathering is the process of something being broken down chemically, like changing the makeup of the rock, or dissolving it.
Water is the most important agent of chemical weathering. It speeds up the process of chemical reactions, and it also contains acids from the atmosphere around it.
Chemical weathering doesn't work as well on some rocks because of the composition of the rock. Others may dissolve easier.
Spheroidal weathering is when the edges of the rock is rounded own, giving the rock a smoother look. An example is when the of this is when water runs down the sides and joints/cracks in the rock and smooth the edges, weathering them down rapidly.
Another example of chemical weathering is rust. this happens when iron reacts to the oxygen in something around it, and gives it an orange-brown, or rusty, color
The aluminum, silicon, and oxygen in silicate minerals usually combine with water and produce clay The rate of weathering
The rate of weathering changes with the characteristics of the rocks. Things like cracks give more surface area to water, quickening the rate of weathering. There are many other factors such as the temperature, weather, and climate. Soil has 4 major parts, mineral matter, or broken rocks, organic matter, or humus, water, and air.
There is about 45% mineral matter, 5% humus, 25% air, and 25% water. however, the percentage of humus varies greatly when in different types of soils. Soil texture varies with the diferent sizes of the particles in the soil. Soil is made up of 3 main parts, clay, sand, and silt. Clay and silt make it harder for plants to grow. Loam is the perfect type of soil for plants. There isn't a dominate portion, it is evenly mixed between clay, sand, and silt for the purpose of plants growing. Important factors to soil formation are parent material, time, climate, organisms, and slope. Parent material is the source of the mineral matter in the soil. Time allows for the soil to become thicker. the climate has the greatest affect, for it can cause precipitation, temperatures, moisture in the air, and other influences to chemical and mechanical weathering. organisms may burrow, causing holes, or give off certain minerals that can help or hinder the soil's rate of development. Also, bacteria can aid with soil fertility and other things, like decomposing dead organisms. Slope can affect the types of erosion, water runoffs, and other such activities. Soil varies in texture, structure, and color at different depths. These different sections are known as soil horizons. Horizon A is just underneath the topsoil, With horizon B below that, and C is below that. Just below C is bedrock, or the parent material. 3 common types of soil are pedalfer, pedocal, and laterite.
Pedalfer: receives more than 63cm of rain a year, found in temperate areas, and common in the eastern U.S. Its B horizon contains large amounts of iron oxide and aluminum rich clays. It is a red-brown color.
Pedocal: drier, bush vegataion. conatins less clay than pedalfers because of drier areas, slowing chemical weathering. large amounts of calcite, and is usually light brown.
Laterite: warm and wet areas, chemical weathering increases, so laterite is a deeper soil. water removes calcite and silica, leacing behind iron exide and aluminum oxides. Creates good bricks because of its waterproof quality when dry. It is an orange or red color. Soil is necessary for growth, even though it is a small part of the minerals on earth. Water can dislodge part of the soil, and carries it away. Thin sheets of water moving across the soil and eroding it is called sheet erosion. Recently, the rate that soil has been weathering away has increased. this is due to human activities that remove natural vegetation, such as farming, logging, and construction. Wind erodes soil slower than water does, and soil has begun to erode faster than it is being produced. Reservoirs are starting to collect sediments in the bottom, making them less useful for storing water, controlling floods, and generating electricity. Some Soil is now carrying pesticides, causing the water to be contaminated with those chemicals, causing animals that use live on or use water, like humans, to be at risk. also, the soil may be bringing to many nutrients into lakes, causing plant life become more abundant, and accelerates the process that kills the lakes. We cannot stop soil erosion completely, but we have been working on improving it. A misunderstanding of rainforest soil has caused massive erosion in the rain forests, leaving many acres of land severely leached, and it can not be used further. Leaching is when minerals get leached out of the soil
by water. Triggers of mass movements include: water, oversteepened slopes, removal of vegetation, and earthquakes. Water can saturate the surface of the earth, causing mudflows. It can either slowly or quickly carry away the minerals in massive proportions at a time. overtseepend slopes causes gravity to get a better hold on the minerals, and something can then pass by and quickly dislodge some minerals, leading to a chain reaction that causes mass movements. Removal of vegetation causes the roots that were holding the soil together dissapear, making those areas more susceptible to other triggers. Earthquakes can dislodge minerals and other materials, causing mas movements, and can make it happen several times because of after shock, which will hit the area again. There are 5 main types of mass movements: rockfalls, slides, slumps, flows, and creeps. Rockfalls are when rocks and/or rock fragments go free falling through the air. This is common on oversteepend slopes, where the material is not secure on the surface. They are also caused by freeze thawing and roots, and they can sometimes trigger other mass movements. A slide is a block of material the moves suddenly along a flt, inclined surface. If a slide includes bedrock, it is called a rockslide. they often occur on mountain tops. Rockslides are the fastest type of mass movement, and can move with speeds over 200km per hour. A slump is the movement of a block of material along a curved surface. This doesnt happen quickly, and usually doesnt move very far. Thick accumulations of clay and slopes help cause these. There are two types of flows, mudflows and earthflows. mudflows are caused by a heavy downpour, which mixes loose minerals and carries them down hill. An earthflow move slowly, anywhere from 1mm to several meters. These happen when water saturates the ground, and the saturated area starts to slide across the ground. Creeps are the slowest type of movement, which travels a few mm to a few cm a day. A factor is freezing and thawing. Freezing expands the water in the soil, lifting particles, and thawing contracts them and they fall back to a slightly lower level. each time. creeps are so slow that they are very hard to notice, and can be seen through things that were once parallel to the ground starting to slope. Chapter 6 Running Water and Ground Water Water is constantly moving throughout the atmosphere and on the earth. This is called the water cycle 6.1 Running Water The water cycle is the unending cycle of how the water is cycled throughout the earth's systems. This is possible because water can be a liquid, solid, or gas, and readily changes between these states of matter. It is a gigantic worldwide system that circulates the earth's water supply. The water cycle has several main parts parts to it. To start, water evaporates from lakes, oceans, and rivers from the heat of the sun. The evaporated water is then carried around the world from the by wind, and eventually condenses to form clouds. The clouds give off precipitation, such as rain, snow, and hail. This falls onto the earth and either forms streams, rivers, lakes, and other bodies of water or sinks into the ground, or infiltrates it. Infiltration is the movement of surface water into rock or soil through cracks and pore spaces. This gradually seeps into a body of water. Transpiration is the act of plants absorbing and then releasing it back into the atmosphere. Glaciers hold large amounts of water and form when the water falls in a cold enough place to 6.2 The Work of Streams Vocabulary
Inflitration:movement of surface water into rock or soil though cracks and pore spaces.
Transpiration: plants absorb water and release it into the atmosphere
Gradient: slope or steepness of a stream of a certain distance
Stream channel: the coutse the water in a stream flows
Discharge: volume of water flowing past a certain point is the stream during a certain interval of time.
Tributary: a stream that tributes its water to a larger stream.
Base level: the lowest the stream can erode its channel
Meanders: when a stream channel forms a course with a lot of bends, the bends are called meanders. Erosion Floods Drainage Basins Streams generally erode their channels by lifting loose particles by abrasion, grinding, and by dissolving soluble material. the materials that are released into the water are then transported downstream through the dissolved load, suspended load, or the bed load Dissolved load: most of the dissolved load enters streams through groundwater. Some enters through dissolving rocks. it is expressed in ppm, or parts of dssolved material per million parts of water. Suspended load: the suspended load is the visible cloads of semident in the water. This is how the largest part of a stream's load is carried. Bed load is the rocks and sediments to large to float in the stream. the bed load is not always moving, like the other loads. This is becasue the bed load needs enough water force from the river to move it along. The competence of a steam measures the largest paricle it could carry, and the capacity is the maximum load it can carry. Deposition and Stream Valleys Deposition Stream Valleys Deposition is when the streamloses its velocity and can no longer carry sediments of a particular size, and these sediments settle at the bottom of the stream. Deltas and natural levees are examples of this. A delta is an accululation of sediments formed where a stream enters a lake or ocean. a delta grow outward, the stream's gradient lessens and the water slows. The channel becomes choked with dropped sediments settling out of the slow moving water. The river than moves around the obstacles, spreading out in many directions to find the base level. A natural levee is a ridge made from coarse materials parallel to the stream. They form when a river rapidly overflows, losing velosity and dropping sediments on these strips of land A v-shaped shaped valley shows the stream's primary work has been reaching it's base level. Waterfalls occur when one part of the base erodes faster than the before ground, and rapids are due to similar weaknesses. When a stream cuts side-to-side, a large, wide valley is formed with a flat floor, or a floodplain. When the river floods, the floodwater floods out, into this plain. Streams on this plain meander along. When a meander's connection to the main stream is cut off by silt, clay, and other materials, it becomes an oxbow lake. A flood is the when the discharge of a stream becomes so great that it exceeds the capacity of its channel and overflows its banks. Floods are the most common, and the most destructive, of all natural geological hazards. They are generally caused in the spring, by rapid snowmelts from snow, or after a heavy rainstorm. To control flood damage, peple have created artifical levees, flood control dams, and place lmits on development on floodplains. Artificial levees are earthen mounds built on the banks of the river, designed to stop the water from overflowing its banks. Flood control dams store floodwater in lakes, and control the amount of water in the river so it is much less likely to flood. they also have hydro power plants, and use the passing water as a source for energy. By limiting the amount of development and buildings on a floodplain, it is also limiting the amount of damage than can be caused to those buildings. The building of dams and natural levees is so that they can build more on floodplains. Drainage basins is the and surrounding a stream that contributes its water to the stream. Imaginary lines called divides split one basin from another. Drainage basins vary largely in size. From small divides for tiny streams, to a continental divide, which splits continents into several different drainage basins. The Mississippi River drainage basin is the largesy in North America 6.3 Water Beneath the surface Distributing and Movement of Water Undergound Distribution: Some water soaks into the ground, but doesn't travel far. The molecular structure makes it cling to the soil as a film of covering. This is called the belt of soil moisture. The zone of saturation is the area beneath the surface with open space filled with water. Groundwater is the water in this zone. The top of this is called the water table. water can only be pumped into wells from below the water table.
Movement: Porosity is the percentage of the total amount of rocks and soil with pores filled with water. Water moves slower through the ground if pore spaces are smaller, and permeable material allows liwuids to pass though. Clay has high porosity and is impermeable, because water can't move through this soil. aquifers are permeable layers of rocks and sediments that transfer water freely. They are also the source of well water. Springs When the water table intersects with the ground surface, a spring forms. In other words, a spring is naturally flowing water on the surface, from the zone of saturation. Hot springs are springs that are springs that are roughly 6 to 9 degrees C higher than the average air temperature. The United States has over 1000 hot springs. A geyser is hot water in a natural fountain, were the water shoots up periodically in columns of stream from 30 to 60 meters high. After that, the water than seeps back into the ground, and it all happens again. A well known geyser is Old Faithful in Yellowstone National park. A well is a hole bored into the zone of saturation. In the United States, the biggest use of wells is irrigation: 65%. The water table lowers faster than it is refilled. It drops when substantial amounts of water are taken from the zone of saturation, and drops in a cone around the well. An artesian well is when the groundwater raises from its own pressure. Two conditions must first exist. 1: the water is an a aquifer tilted so that on end is exposed on the surface and the other isn't. 2: aquitards above and below so the water doesnt escape. The resulting pressure forces the water to rise. There are a 2 major environmental problems with groundwater. One: Overuse. by using groundwater to much, it starts withdrawing, because it is being used faster than it replenishes. And Two: Contamination. Sewage, fertilizers, and other such chemicals are things that contaminate groundwater and render it unusable. This can be fixed naturally by filtering the water through sand and other course materials. Groundwater can erode some rocks, mainly limestone, underground and create caverns. caverns are naturally formed, and are formed either above or below the water table. A limestone called tavertine is the result of dripping water leaving behind calcium carbonate. Stalagmites are found on the floor of a cavern, and are were the water falls from stalactites, the dripstones on the top of the cavern. Karst topography is a type of lanscape that is that has a layer of limestone, and other soluble rocks, beneath the surface. The limestone erodes, causing the ground to be filled with sinkholes and the ground usually uneven and irregular. Chapter 7 glaciers, Deserts, and Wind. 7.1 Glaciers Types of Glaciers Glaciers are thick ice masses that move slowly over the land surface of the earth. An ice age is a period of time when glaciers cover much of the earth's land area. Ice sheets are large glaciers in regions of extreme cold, and move in all directions instead of just one, and are giant in comparison to valley glaciers. Valley glaciers are ice masses that slowly move down valleys that were once occupied by streams. The valley turns into a U-shape instead of the previous V-shape. They form and move mainly in mountains. A snowline is thee lowest area that is covered by snow year long. How Glaciers Move Glacial movement is called the glacier flow. It can either have a plastic flow or a basal slip. Plastic Flow Basal Slip Plastic flow happens when the ice of a glacier is under enough pressure that it begins to distort and change shape. The weight from the ice on top causes the ice underneath to flow. Plastic flow begins at about 50 meters deep. Basal slip is when gravity pulls the glacier down, making it slip and slide down the hillside. Different glaciers move at different rates, depending on the rate of gaining and losing of ice. Some grow so slowly that vegetation grows on top of these glaciers. The top part of the glacier does not behave the same as the bottom parts, as it is made of more brittle ice. The resulting tension when the bottom part moves over more rough terrain causes crevasses and cracks to form along the top of the glacier. These are often hidden by snow. The budget of the glacier is the balance between the accumulation, or gaining, of snow at the top, and the loss, or wastage, at the bottom of the glacier. Glacial Erosion Glaciers erode in 2 different ways: plucking and abrasion. Plucking is is when the glacier loosens and then picks up loose rocks from ground. abrasion is when the glacier and its load slide of the bedrock. The affect is similar to that of sand paper, scratching the surface of the bedrock and smoothening it out. The ground away rocks form a powdery types substance called rock flour. When large rocks are at the bottom of the glacier, long gouges and scratches form in the bedrock. Landforms Created by Glaciers Before a galcier moves through a valley, the valley is usually V-shaped. Afterwords, the U-shaped valley left behind is called the glacial trough. The amount of change and erosion in the valley depends on the size of the glacier. A cirque is a bowl shaped depression at the head of a glacial valley that is surrounded on three sides by rocks. Horns are mountain peaks, taller than the surrounding land, an obstacle that the glacier moved around instead of over. An arete is a long, sharp edged ridge also left behind by glaciers. Glacial Deposits Glacial Drift is any type of glacial sediment, no matter how, where, or in what form they were deposited.
There are two types of glacial drift: till and stratified drift. Till is material deposited directly by the glacier. It is deposited as the glacier melts or drops some of its rock debris. Till is usually unsorted, and has particles of any size. Stratisfied drift is sediment laid down by glacial meltwater. Unlike till, this is sorted because of the water it has been running in. It often consists of sand and gravel because meltwater can't move boulders. The mineral content of till is often different the the surrounding bedrock, suggesting that it was carried there from somewhere else. Moraines, Outwash Plains, and Kettles Lateral Moraines: The debris left on the sides of the glacier as it progresses
End Moraines: When a glacier stops at one point, the ice inside is still moving, distributing debris to the ground at the end of the glacier. When the glacier recedes, this pile is left.
Gound Moraines: Similar to end moraines, a ground morain is the debris left behind when a glacier is receding, except that this is on the trail that it follows as it recedes.
Terminal Moraines: As a glacier melts, it leaves a series of end moraines. The farthest end moraine is the terminal end moraine.
Recessional Moraines: The end moraines left behind a glacier that are not the terminal moraine are called recessional end moraines.
Outwash Plains: The meltwater from the glacier carries out the finer sediments, and deposits them over a ramp like plain called the outwash plain.
Kettles: The small lakes and depressions left in end moraines and outwash plains.
Drumlins are streamline hills composed of till.
Eskers: gravel and and left from the small streams that had been running under the glacier. Glaciers of the Ice Age During an ice age, glaciers cover 30% of the land. This explains many of the world's deposits of sediments and minerals. More glaciers and such were found in the northern hemisphere, as the southern hemisphere has a lot less land than the nothern, and was mostly contained in Antarctica. The most recent ice age began 2-3 million years ago, durring which many now extinct animals like whooly mammoths and saber tooth tigers roamed the earth's ice sheets. When the ice started to melt at the end of the ice age, it all happened close to the same time, and flooded the oceans. Also, the glaciers left a reformed land, with added features such as the Great Lakes. It changed the climate in many places as well. 7.2 Deserts 7.3 Landscapes Shaped by Wind Geological Processes in Arid Climates In a desert, chemical weathering happens in small amounts, while mechanical weathering is much more common. The rust colored stain in a desert is the result of chemical weathering, and when given enough time, clays and thin soils do form. Mechanical weathering is more common, but is still greatly reduced in deserts. Rock weathering is cery limited due to In most regions, you can find several permanent streams. In a desert, you are lucky to find one that is still there. Ephemeral streams, or streams that only contain water just after it rains, are much more common. And in a desert, they only contain water for several hours or days a year. These streams are also known for their dangerous flash flooding. Because of the small amount of vegetaion to hold the soil together, a flash flood brings a lot of change with it, carrying of the top of the dirt, and depositing it elsewhere. So while water erosion doesn't happen often, it still plays a large roll in the desert. Basin and Range: A Desert Landscape Deserts usually have an interior drainage system. This means that when it rains, the water runs off the nearby mountains, carrying sediments and deposit them over an alluvial fan. at the mouth af the canyon the water was running through. Occasionally, there is abundant rainfall, or snowmelt, or a large amount of water running down the canyon. this water may flow across the alluvial plain and into the center of the basin, or area of the desert, and form a shallow playa lake. This lake lasts a few days, and maybe a few weeks before it evaporates or sinks into the ground, and the resulting lake bed is a playa. There is also few rare rivers, such as the Nile and Colorado, that flow across a desert. these rivers have to have a steady income of water, and enough water to begin with that it doesn't dry out. While running water is infrequent, it is a very important force. Most desert erosion is a result of running water. More significant than wind erosion in deserts. Wind erosion is an important part of the world, even though it does not come close to the power of water erosion. Wind erodes in 2 different types of ways, deflation and abrasion. Deflation: is the lifting and removing of particles such as clay and silt. Sand droll and skip along the surface in a process called saltation. deflation can lower the land, like what happened in the Dust Bowl. Constant erosion can cause blowouts, small holes in the ground from the size of a dimple to huge holes in the ground. This causes a harder ground and forms desert pavement, a stony surface in the desert Abrasion: Wind blown sand cuts and polishes rock surfaces. This can blast them into odd shapes, but close to the ground, as sand does not go much higher than a meter above the surface. It has been known to cut though the bottom of telephone poles. 2 types of landforms caused by wind are loess and sand dunes. Loess is windblown silt that blankets the landscape. A sand dune is a ridge of wind deposited sand, and they are usually steeper on the sheltered side than the wind-blown side. There are have 6 main shapes. Barchan dunes are crescent shaped. They move slowly, and reach a height of about 30 meters. If there is a constant wind direction, it stays symmetrical. Transverse dunes are dimes that form in a series of long ridges. found mainly in coastal areas. Barchanoid dunes are the phase between barchan and transverse; long ridges with small crescent shapes Longitudal dunes are long ridges of sand that form parallel to the wind. Can reach up to 100m high Parabolic dunes look like backward barchan, except their tips point into the wind. Needs some vegetation to form Star Dunes are isolated hills of sand with a star shaped base. The wind direction is cariable, and some reach 90m in height. Chapter 8 Earthquakes and the Earth's interior An earthquake is the vibrations produced by a rapid release of energy in the lithosphere. This is caused by a slipping along a fault, or break in the lithosphere. The focus of an earthquake is the point where it starts. The energy released from the slipping of the fault is called seismic waves, and spreads out in every direction from the focus The epicenter of an earthquake is the location on the surface directly above the focus The elastic rebound hypothesis says that the energy builds up on both sides of the fault, and suddenly releases all at once, causing the earthquake and seismic waves Aftershocks are little quakes that come after the earthquake, and foreshocks come before There are several ways to measure an earthquake, and many factors There are 2 main types of seismic waves-body waves and surface waves. Body waves are either P waves or S waves P waves push and pull particles in the direction that they travel. they travel faster than S waves S waves shake particles at right angles to the wave's direction of travel. if you take a rope and shake it from one end to another, it looks similar to S waves. S waves cannot travel through liquids A body wave produces a surface wave when it reaches the surface. They travel slowly, and move up and down as well as side to side. These are the most destructive of seismic waves, and are larger than body waves. A seismograph is a device to record seismic waves. It is a weight on a support attached to bedrock. As the waves shake, the weight stays at the same place, and it records the amount of shaking the seismic waves cause A seismogram is the record of the ground motion produced by the seismograph. A richter scale measure an earthquake by the size of the largest wave, and is no longer commonly used. The scale that has replaced the Richter scale is called the moment magnitude scale. it estimates the energy released from the earthquake instead of the seismic waves. A time-travel graph takes the data from several different placees, and can be used to determine the epicenter of an earthquake from these several graphs. Earthquakes can lead to other hazards, such as seismic shaking, liquefaction, landslides, mudflows, and tsunamis Seismic Shaking is the shaking caused by seismic waves, and can cause massive damage to unreinforced structures. Strongest near the epicenter, but can be magnified in loose or filled soil. Liquefaction is when the stable soil turns to liquid, and can make buildings and bridges sink into the ground, as well as underground tanks float Earthquakes can trigger mass movements, such as landslides and mudslides. Tsunamis are also a very real danger. A tsunami is a wave formed when the ocean floor shifts suddenly during an earthquake or volcanic eruption, sending a mass wave of destruction to surrounding coasts. A tsunami can range in size from a few meters to 30 or more meters high. A tsunami warning system has been set up around the coastal edges of the Pacific Ocean to help save lives Reducing earthquake damage can happen in several ways, finding possible locations for earthquakes, reinforcing buildings, and much more. By looking at records of previous earthquakes, scientists can predict areas that earthquakes can happen. However, they have not yet been able to predict when they will happen. There are some different ways that buildings have been reinforced in preparation for a possible earthquake. Some of these are steel cross braces and base-isolators, or pads made of steel and steel to help obsorb some of the energy from the seismic waves. Besides this, basic safety procedures to the people in earthquake danger zones. The basic rule is to drop, cover, and hold. Get next to something taller than you and cover your head. Stay closer to the inside of the building. The earth has 3 major layers: the crust, mantle, and core. The crust is the thin, rocky, outer layer that we live on.
The mantle is a hug amount of rock underneath the crust. It contains over 82% of the earth's volume, and is different from the crust because of its chemical composition.
The core is an iron-nickel alloy, with 2 parts. the outer part is molten, and the extreme pressures on the inner part make it solid metal Some layers are defined by physical properties. Theses are the lithosphere, athenosphere, lower mantle, and the inner and outer cores Lithosphere is the outermost layer, and is a rigid layer around the earth, going to about 10 kilometers below the surface
Athenosphere: A soft, weak layer containing rocks that are almost at melting temperatures. The athenosphere is a part of the outer mantle
Lower mantle: The lower mantle is the lower part of the mantle, and is more rigid than the athenosphere. The rocks in the lower mantle are very hot and can gradually flow.
Outer core: a layer of molten iron-nickel alloy surrounding the inner core. This layer generates the Earth's magnetic field.
Inner core: The center of the earth, and is made of a solid metal despite high temperatures because of the extreme pressure compressed upon it. This is also a layer of an iron-nickel alloy Discovering the earth's layers and composition. The discovery of the earth's layers comes from studying the path of P and S waves. Scientists have traced the paths of seismic waves and found that where the paths change, there is a different layer in the earth. They have also named the boundaries between the layers, such as the crust and the mantle is called Moho, or Mohorovicic. The composition of the layers was discovered by studying seismic data, rock samples, meteorites, and high pressure experiments. Seismic data and rock samples show that the continental crust is mainly made of low-density granite, and the ocean is composed of basaltic rocks. Meteorites are assumed to be made of generally the same materials as the earth was when it was formed. so metallic meteorites have a similar composition as the earth, and geologists believe that the density of iron caused it and other materials like it to sink to the center of the earth while it was formed.