原版英语RAZ 教案Q45-Sinkhole Science (3).pdf
www.readinga-Visit www.readinga- for thousands of books and materials.LEVELED BOOK QWritten by Sean McCollumSinkhole ScienceA Reading AZ Level Q Leveled BookWord Count:1,033www.readinga-Photo Credits:Front cover:REUTERS/Casa Presidencial;back cover:Stephen Frink Collection/Alamy;title page:ian woolcock/Alamy;page 3:Mark Costantini/San Francisco Examiner/AP Images;page 4:REUTERS;page 8:Brian Peterson/ZUMA Press/Corbis;page 10:George Steinmetz/Corbis;page 12:Larry McCormack/The Tennessean/AP Images;page 13:courtesy of USGS,Open-File Report 2004-1352;page 14:Matt Smith/The Express-Times/AP Images;page 15:Danita Delimont/AlamyIllustration Credits:Pages 7,9:Learning AZ/Laszlo VeresTitle page:Umpherston Sinkhole Gardens,South AustraliaBack cover:The Great Blue Hole is a sinkhole off the coast of Belize in the Caribbean Sea.It is the largest ocean sinkhole in the world.Its depth creates its deep blue color.Written by Sean McCollumCorrelationLEVEL QN3030Fountas&PinnellReading RecoveryDRASinkhole ScienceLevel Q Leveled Book Learning AZWritten by Sean McCollumAll rights reserved.www.readinga-Sinkhole Science34Table of ContentsTwo Huge Holes .4What Causes Sinkholes?.5Two Types .6Amazing Sinkholes .10Sinkholes Caused by Humans .11Dealing with Sinkholes .13Conclusion .15 Glossary .16Two Huge HolesFor a few weeks in 2007,people in a neighborhood of Guatemala City felt the ground tremble and shake.No one knew what was causing it.Then on February 23,a huge hole suddenly opened in the street.A dozen houses tumbled into the pit,and several lives were lost.The hole was more than 330 feet(100 m)deepdeep enough to swallow two Statues of Liberty.The 2007 Guatemala City sinkholeA house slides into a giant sinkhole in San Francisco in 1995.Sinkhole Science Level Q34Table of ContentsTwo Huge Holes .4What Causes Sinkholes?.5Two Types .6Amazing Sinkholes .10Sinkholes Caused by Humans .11Dealing with Sinkholes .13Conclusion .15 Glossary .16Two Huge HolesFor a few weeks in 2007,people in a neighborhood of Guatemala City felt the ground tremble and shake.No one knew what was causing it.Then on February 23,a huge hole suddenly opened in the street.A dozen houses tumbled into the pit,and several lives were lost.The hole was more than 330 feet(100 m)deepdeep enough to swallow two Statues of Liberty.The 2007 Guatemala City sinkholeA house slides into a giant sinkhole in San Francisco in 1995.Sinkhole Science Level Q56In 2010,it happened again,fifteen blocks from the first hole.This time,the hole swallowed a three-story clothing factory and left another gaping chasm in a major intersection.Miraculously,no one was injured.Sinkholes happen all over the world,in the middle of cities and in the middle of nowhere.Though sinkholes take years to form,each time a new sinkhole opens up in the earth,it takes people by surprise.What Causes Sinkholes?The ground we stand on feels solid.Underground,however,a lot is happening.Water trickles and flows,slowly eroding rocks and soil.This creates underground spaces.These result in sinkholes.Sinkholes dont happen just anywhere,though.Most natural sinkholes form where there are certain kinds of soft bedrock.Bedrock is a layer of underground rock.The ground above it and on the surface is called the overburden.Rain or underground water drips and flows into this bedrock and erodes it.This creates open spaces such as underground caves or caverns.Over time,these spaces get bigger.Eventually,the overburden may slowly drop down to form a sinkhole.Sometimes,though,sinkholes can open suddenly and swallow buildings,cars,and people.Two TypesThere are two main types of sinkholes.The first is a cover-subsidence sinkhole(subside means to sink or settle).A cover-subsidence sinkhole forms when water wears a space in the underground bedrock.The overburden above the bedrock then shifts downward.Most sinkholes of this kind form slowly and may measure only a few yards across.The overburden may contain a lot of sand that easily slides into the underground space.These sinkholes often create a bowl shape on the surface.They may become ponds or wetlands if water has no way to drain out.Sinkhole Science Level Q56In 2010,it happened again,fifteen blocks from the first hole.This time,the hole swallowed a three-story clothing factory and left another gaping chasm in a major intersection.Miraculously,no one was injured.Sinkholes happen all over the world,in the middle of cities and in the middle of nowhere.Though sinkholes take years to form,each time a new sinkhole opens up in the earth,it takes people by surprise.What Causes Sinkholes?The ground we stand on feels solid.Underground,however,a lot is happening.Water trickles and flows,slowly eroding rocks and soil.This creates underground spaces.These result in sinkholes.Sinkholes dont happen just anywhere,though.Most natural sinkholes form where there are certain kinds of soft bedrock.Bedrock is a layer of underground rock.The ground above it and on the surface is called the overburden.Rain or underground water drips and flows into this bedrock and erodes it.This creates open spaces such as underground caves or caverns.Over time,these spaces get bigger.Eventually,the overburden may slowly drop down to form a sinkhole.Sometimes,though,sinkholes can open suddenly and swallow buildings,cars,and people.Two TypesThere are two main types of sinkholes.The first is a cover-subsidence sinkhole(subside means to sink or settle).A cover-subsidence sinkhole forms when water wears a space in the underground bedrock.The overburden above the bedrock then shifts downward.Most sinkholes of this kind form slowly and may measure only a few yards across.The overburden may contain a lot of sand that easily slides into the underground space.These sinkholes often create a bowl shape on the surface.They may become ponds or wetlands if water has no way to drain out.Sinkhole Science Level Q78The second type is a cover-collapse sinkhole.This sinkhole forms when a space gets bigger and bigger under the surface.The overburden gets thinner as dirt,sand,and other sediment fall into the space.The ground around this kind of sinkhole may contain a lot of sticky clay.Clay helps hold the overburden together.Without warning,though,the surface may collapse into the underground space.Areas that get a lot of sinkholes usually have bedrock made of karst.Karst is made of any type of rock that dissolves easily,such as limestone.Karst can also be formed of gypsum,dolomite,salt,or other minerals and rocks.Karst has many holes and cracks that water can flow into.When rainwater soaks into the earth,it picks up a mild acid from leaves and plants.The mild acid dissolves karst.This helps create the underground spaces that cause natural sinkholes.Sinkholes that collapse without warning sometimes pull buildings and vehicles into them,as did this sinkhole in Duluth,Minnesota,in 2012.1 Water dissolves some types of bedrock.The result is an underground cavity.2 Sediments from above spill into the bedrock cavity.As a result,the surface begins to sink.3 Slow downward erosion creates a surface bowl.If water collects here,the bowl may become a pond or wetland.111133332222Cover-Subsidence SinkholeCover-Subsidence SinkholeSinkhole Science Level Q78The second type is a cover-collapse sinkhole.This sinkhole forms when a space gets bigger and bigger under the surface.The overburden gets thinner as dirt,sand,and other sediment fall into the space.The ground around this kind of sinkhole may contain a lot of sticky clay.Clay helps hold the overburden together.Without warning,though,the surface may collapse into the underground space.Areas that get a lot of sinkholes usually have bedrock made of karst.Karst is made of any type of rock that dissolves easily,such as limestone.Karst can also be formed of gypsum,dolomite,salt,or other minerals and rocks.Karst has many holes and cracks that water can flow into.When rainwater soaks into the earth,it picks up a mild acid from leaves and plants.The mild acid dissolves karst.This helps create the underground spaces that cause natural sinkholes.Sinkholes that collapse without warning sometimes pull buildings and vehicles into them,as did this sinkhole in Duluth,Minnesota,in 2012.1 Water dissolves some types of bedrock.The result is an underground cavity.2 Sediments from above spill into the bedrock cavity.As a result,the surface begins to sink.3 Slow downward erosion creates a surface bowl.If water collects here,the bowl may become a pond or wetland.111133332222Cover-Subsidence SinkholeCover-Subsidence SinkholeSinkhole Science Level Q910Amazing Natural SinkholesSinkholes fascinate geologists.They study them to learn more about how water and earth affect each other.Here are three amazing natural sinkholes from around the world.The Qattara Depression is the worlds largest natural sinkhole.It is located in Egypt and is 137 miles(220 km)long and 75 miles (120 km)wide.That is twice the area of the state of Rhode Island.A caver drops into Alabamas Neversink Pit,another one of the worlds amazing sinkholes.Cover-Collapse Sinkhole Cover-Collapse Sinkhole Sediment spills into a cavity in the bedrock.The fallen sediment leaves an arch-shaped hollow in the remaining overburden.Eventually,that thin layer of overburden collapses.The result is a sudden and dramatic sinkhole.The arch-shaped hollow continues to grow until very little overburden remains above it.overburdenbedrocksediment11332244Sinkhole Science Level Q910Amazing Natural SinkholesSinkholes fascinate geologists.They study them to learn more about how water and earth affect each other.Here are three amazing natural sinkholes from around the world.The Qattara Depression is the worlds largest natural sinkhole.It is located in Egypt and is 137 miles(220 km)long and 75 miles (120 km)wide.That is twice the area of the state of Rhode Island.A caver drops into Alabamas Neversink Pit,another one of the worlds amazing sinkholes.Cover-Collapse Sinkhole Cover-Collapse Sinkhole Sediment spills into a cavity in the bedrock.The fallen sediment leaves an arch-shaped hollow in the remaining overburden.Eventually,that thin layer of overburden collapses.The result is a sudden and dramatic sinkhole.The arch-shaped hollow continues to grow until very little overburden remains above it.overburdenbedrocksediment11332244Sinkhole Science Level Q1112Underground mines can also cause sinkholes.Near one Russian city,underground water filled an old mine.The bedrock of salt began dissolving.In 1986,a huge sinkhole opened up.It grew to 780 feet(238 m)deep and covered more area than 25 football fields.It is still growing,and new sinkholes are opening up.Hundreds of people have had to leave their homes.To be safe,the entire city may need to move.Some geologists argue that holes caused by human activity shouldnt be called sinkholes because true sinkholes result from natural processes.Chinas Xiaozhai Tiankeng is considered the deepest sinkhole in the world.More than 2,165 feet(660 m)deep,this sinkhole could swallow a 200-story skyscraper.The Sarisarinama sinkholes in Venezuela were discovered in 1961.Scientists have discovered plants and animals inside that are found nowhere else.Sinkholes Caused by HumansSome sinkholes result from underground construction.In cities,tunnels and pipes crisscross under many buildings and streets.If those pipes get old and worn out,they can collapse,allowing liquid to escape and eat away at the ground.Eventually,the pavement caves in.Work crews must check these underground spaces regularly to make sure they are solid.If a sinkhole forms in a city it can do a lot of damage,as in Guatemala City,where leaking pipes may have triggered the gaping holes in the city streets.Garbage In,Garbage OutPeople sometimes treat sinkholes like garbage dumps.They will throw in junk,trash,even animal waste.This is a terrible idea.Many sinkholes drain into underground water sources.This is the same water that people drink.It is the water that farmers use to water their crops.The result is pollution in our food and drinking water.Loads of garbage hauled from a sinkhole in TennesseeSinkhole Science Level Q1112Underground mines can also cause sinkholes.Near one Russian city,underground water filled an old mine.The bedrock of salt began dissolving.In 1986,a huge sinkhole opened up.It grew to 780 feet(238 m)deep and covered more area than 25 football fields.It is still growing,and new sinkholes are opening up.Hundreds of people have had to leave their homes.To be safe,the entire city may need to move.Some geologists argue that holes caused by human activity shouldnt be called sinkholes because true sinkholes result from natural processes.Chinas Xiaozhai Tiankeng is considered the deepest sinkhole in the world.More than 2,165 feet(660 m)deep,this sinkhole could swallow a 200-story skyscraper.The Sarisarinama sinkholes in Venezuela were discovered in 1961.Scientists have discovered plants and animals inside that are found nowhere else.Sinkholes Caused by HumansSome sinkholes result from underground construction.In cities,tunnels and pipes crisscross under many buildings and streets.If those pipes get old and worn out,they can collapse,allowing liquid to escape and eat away at the ground.Eventually,the pavement caves in.Work crews must check these underground spaces regularly to make sure they are solid.If a sinkhole forms in a city it can do a lot of damage,as in Guatemala City,where leaking pipes may have triggered the gaping holes in the city streets.Garbage In,Garbage OutPeople sometimes treat sinkholes like garbage dumps.They will throw in junk,trash,even animal waste.This is a terrible idea.Many sinkholes drain into underground water sources.This is the same water that people drink.It is the water that farmers use to water their crops.The result is pollution in our food and drinking water.Loads of garbage hauled from a sinkhole in TennesseeSinkhole Science Level Q1314Dealing with SinkholesPredicting where natural sinkholes will form is tricky.The erosion that creates them is usually hidden underground.The type of bedrock is the most important factor in whether or not sinkholes form.Areas with soft bedrock that also get heavy rains are at even greater risk.The rainwater adds weight to the overburden.The draining water can also speed up underground erosion.Tilting trees or signposts can be early clues that the ground is shifting.Growing cracks in walls and sidewalks can also warn that a sinkhole is getting ready to cause trouble.If a sinkhole forms under a house,homeowners can pour tons of dirt and concrete into the hole.This is called grouting.The goal is to plug the hole.Sometimes,though,the dirt and concrete just disappear into the underground space.Another method uses steel rods.These long,strong rods are pushed into solid bedrock deep underground.The rods are then joined to the base of the house.This helps keep the building stable and safe.This United States map shows areas with soft bedrock.These a
