TF阅读真题第947篇Magma

题目：

Magma

 

Magma is a mixture of molten (melted)and semi-molten rock and other solids found beneath Earth’s surface.Melting in Earth requires very specific conditions:the pressure must be just low enough and the temperature just high enough for rock to melt.For example,the center of Earth’s core,6,300 kilometers beneath the surface,is the hottest point in the planet,yet extremely high pressure prevents the solid metal of the inner core from melting. The atoms that make up this metal simply cannot break their bonds to move randomly in a fluid state.A little closer to Earth’s surface, though,the pressure drops and the still very hot outer portion of the core melts.In fact,Earth’s outer core is the largest magma chamber in the solar system.Fortunately for us,this magma is contained by the thick,strong shell of Earth’s crust and mantle-its solid outer layer and the somewhat more fluid layer immediately beneath it.

The lithosphere-the layer formed by the crust and the uppermost part of the mantle-is comprised of individual plates that move in response to the motion of the mantle itself.Earth’s crust and mantle have different melting temperatures than the core,but the pressure and temperature conditions would still keep the mantle solid if it were not for the rising of hot rock into the upper mantle, particularly in those places where the lithosphere’s plates diverge (move away from one another).The rising rock cannot cool fast enough to keep from melting as the pressure drops during its ascent.This process generates most of Earth’s supply of one type of magma known as gabbroic magma.The areas of gabbroic magma production range from 40 kilometers underneath a hot spot near Hawaii to 10-25 kilometers where plates diverge.

The origin of another common type of magma-granitic magma -is much different.It is a product of melting within the crust,not the mantle,developing at“mid-crustal”levels15-25 kilometers deep.Most of this molten material originates from the melting of water-rich rocks where plates converge (come together).Water trapped in rock pores has the property of lowering the melting point of ordinary sandstone-a water-rich rock-by as much as 300 degrees Celsius.All that is needed is heat,and this is readily supplied wherever mantle-derived magma ascends into continental crust.In other words,one kind of magma,gabbroic,causes the formation of another,granitic;rather like a flame that melts wax.

All magma rises because it is less dense than the surrounding solid rock.Below the level of the shallow crust,density contrast is the primary factor that controls the rate of ascent;the greater the difference in density between melt and the surrounding solid rock, the faster magma rises.The initial melt filters along fractures in the surrounding solid rock,eventually accumulating enough mass and buoyancy (the ability to float or rise)to push aside the overlying crust as it rises.Closer to the surface,however,the contrast in density drops to the point where equal volumes of magma and enclosing rock may weigh the same.The magma cannot rise farther in this so-called neutral buoyancy position.Instead,it begins to build up its volume,stretching and inflating the crust in some areas and in other places passively filling the gaps opened by fractures in the earth that occur commonly in those regions where the crust is prone to movement.As the volume of magma increases,great pieces of surrounding rock may detach and settle into the molten chamber,a process called stoping.Small stoped pieces called xenoliths,meaning“foreign rocks,”may be smaller than a coin,whereas larger blocks may be the size of buildings. Some stoped blocks can drop hundreds of meters and partly or wholly melt within the magma,altering the magma chemistry in noticeable ways.Assimilation is the digestion of stoped blocks and surrounding solid rock by magma.Chemical studies show that only a small fraction of any typical magma body consists of assimilated material.The continuously cooling magma simply does not have enough heat to incorporate much new material after it stops rising in the shallow crust.

 

 

 

 

 

 

 

1

Magma is a mixture of molten (melted)and semi-molten rock and other solids found beneath Earth’s surface.Melting in Earth requires very specific conditions:the pressure must be just low enough and the temperature just high enough for rock to melt.For example,the center of Earth’s core,6,300 kilometers beneath the surface,is the hottest point in the planet,yet extremely high pressure prevents the solid metal of the inner core from melting. The atoms that make up this metal simply cannot break their bonds to move randomly in a fluid state.A little closer to Earth’s surface, though,the pressure drops and the still very hot outer portion of the core melts.In fact,Earth’s outer core is the largest magma chamber in the solar system.Fortunately for us,this magma is contained by the thick,strong shell of Earth’s crust and mantle-its solid outer layer and the somewhat more fluid layer immediately beneath it.

Which of the following can be inferred from paragraph 1 about Earth’s inner core?

 

Factual Information Questions事实信息题

 

AIt has a temperature that could easily melt metal at a less extreme pressure.

BIt is at the same temperature as Earth’s outer core.

CIt experiences drops in pressure more often than Earth’s outer core does.

DIt has a high enough pressure to break the bonds between atoms of metals.

2

According to paragraph 1,which TWO of the following are true of Earth’s outer core?To receive credit,you must select TWO answer choices.

 

Factual Information Questions事实信息题

 

Select 2 answers

AIt contains metal atoms that do not break their bonds even at low pressure.

BIts pressure is lower than the pressure of the inner core.

CIt contains more magma than any other area of the solar system.

DIt contains both a solid outer layer and a liquid inner layer.

3

The lithosphere-the layer formed by the crust and the uppermost part of the mantle-is comprised of individual plates that move in response to the motion of the mantle itself.Earth’s crust and mantle have different melting temperatures than the core,but the pressure and temperature conditions would still keep the mantle solid if it were not for the rising of hot rock into the upper mantle, particularly in those places where the lithosphere’s plates diverge (move away from one another).The rising rock cannot cool fast enough to keep from melting as the pressure drops during its ascent.This process generates most of Earth’s supply of one type of magma known as gabbroic magma.The areas of gabbroic magma production range from 40 kilometers underneath a hot spot near Hawaii to 10-25 kilometers where plates diverge.

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage?Incorrect choices change the meaning in important ways or leave out essential information.

 

Sentence Simplification Questions句子简化题

 

AWithout the rising of hot rock into the upper mantle,particularly in areas where plates diverge,certain conditions would keep the mantle solid.

BHot rock rising into the upper mantle becomes solid due to the different pressure and temperature conditions of the crust and mantle.

CIn places where the lithosphere’s plates diverge,temperature and pressure conditions allow hot rock to rise through the mantle and into the crust.

DBecause Earth’s crust and mantle have different melting temperatures than the core,hot rock rises into the upper mantle in places where the plates move away from one another.

4

The origin of another common type of magma-granitic magma -is much different.It is a product of melting within the crust,not the mantle,developing at“mid-crustal”levels15-25 kilometers deep.Most of this molten material originates from the melting of water-rich rocks where plates converge (come together).Water trapped in rock pores has the property of lowering the melting point of ordinary sandstone-a water-rich rock-by as much as 300 degrees Celsius.All that is needed is heat,and this is readily supplied wherever mantle-derived magma ascends into continental crust.In other words,one kind of magma,gabbroic,causes the formation of another,granitic;rather like a flame that melts wax.

The author mentions“a flame that melts wax”in order to

 

Rhetorical Purpose Questions修辞目的题

 

Aexplain why granitic magma can only form at mid-crustal levels

Bdemonstrate the difference between gabbroic and granitic magma

Csupport the claim that heat is all that is needed for sandstone to melt

Dillustrate the role of gabbroic magma in the development of granitic magma

5

The origin of another common type of magma-granitic magma -is much different.It is a product of melting within the crust,not the mantle,developing at“mid-crustal”levels15-25 kilometers deep.Most of this molten material originates from the melting of water-rich rocks where plates converge (come together).Water trapped in rock pores has the property of lowering the melting point of ordinary sandstone-a water-rich rock-by as much as 300 degrees Celsius.All that is needed is heat,and this is readily supplied wherever mantle-derived magma ascends into continental crust.In other words,one kind of magma,gabbroic,causes the formation of another,granitic;rather like a flame that melts wax.

According to paragraph 3,which of the following is true of water-rich rocks?

 

Factual Information Questions事实信息题

 

AThey release trapped water when plates converge.

BThey melt at a lower temperature than rocks that are not filled with water.

CThey are more common in the mantle than in the crust.

DThey begin to melt at 300 degrees Celsius at mid-crustal levels.

6

All magma rises because it is less dense than the surrounding solid rock.Below the level of the shallow crust,density contrast is the primary factor that controls the rate of ascent;the greater the difference in density between melt and the surrounding solid rock, the faster magma rises.The initial melt filters along fractures in the surrounding solid rock,eventually accumulating enough mass and buoyancy (the ability to float or rise)to push aside the overlying crust as it rises.Closer to the surface,however,the contrast in density drops to the point where equal volumes of magma and enclosing rock may weigh the same.The magma cannot rise farther in this so-called neutral buoyancy position.Instead,it begins to build up its volume,stretching and inflating the crust in some areas and in other places passively filling the gaps opened by fractures in the earth that occur commonly in those regions where the crust is prone to movement.As the volume of magma increases,great pieces of surrounding rock may detach and settle into the molten chamber,a process called stoping.Small stoped pieces called xenoliths,meaning“foreign rocks,”may be smaller than a coin,whereas larger blocks may be the size of buildings. Some stoped blocks can drop hundreds of meters and partly or wholly melt within the magma,altering the magma chemistry in noticeable ways.Assimilation is the digestion of stoped blocks and surrounding solid rock by magma.Chemical studies show that only a small fraction of any typical magma body consists of assimilated material.The continuously cooling magma simply does not have enough heat to incorporate much new material after it stops rising in the shallow crust.

The word“detach”in the passage is closest in meaning to

 

Vocabulary Questions词汇题

 

Amelt

Bexplode

Cbreak off

Dcollide

7

All magma rises because it is less dense than the surrounding solid rock.Below the level of the shallow crust,density contrast is the primary factor that controls the rate of ascent;the greater the difference in density between melt and the surrounding solid rock, the faster magma rises.The initial melt filters along fractures in the surrounding solid rock,eventually accumulating enough mass and buoyancy (the ability to float or rise)to push aside the overlying crust as it rises.Closer to the surface,however,the contrast in density drops to the point where equal volumes of magma and enclosing rock may weigh the same.The magma cannot rise farther in this so-called neutral buoyancy position.Instead,it begins to build up its volume,stretching and inflating the crust in some areas and in other places passively filling the gaps opened by fractures in the earth that occur commonly in those regions where the crust is prone to movement.As the volume of magma increases,great pieces of surrounding rock may detach and settle into the molten chamber,a process called stoping.Small stoped pieces called xenoliths,meaning“foreign rocks,”may be smaller than a coin,whereas larger blocks may be the size of buildings. Some stoped blocks can drop hundreds of meters and partly or wholly melt within the magma,altering the magma chemistry in noticeable ways.Assimilation is the digestion of stoped blocks and surrounding solid rock by magma.Chemical studies show that only a small fraction of any typical magma body consists of assimilated material.The continuously cooling magma simply does not have enough heat to incorporate much new material after it stops rising in the shallow crust.

According to paragraph 4,magma stops rising when

 

Factual Information Questions事实信息题

 

Ait flows into fractures in the surrounding rock

Bit becomes full of pieces of the surrounding rock

Cits weight is the same as that of the surrounding rock

Dits temperature is the same as that of the surrounding rock

8

All magma rises because it is less dense than the surrounding solid rock.Below the level of the shallow crust,density contrast is the primary factor that controls the rate of ascent;the greater the difference in density between melt and the surrounding solid rock, the faster magma rises.The initial melt filters along fractures in the surrounding solid rock,eventually accumulating enough mass and buoyancy (the ability to float or rise)to push aside the overlying crust as it rises.Closer to the surface,however,the contrast in density drops to the point where equal volumes of magma and enclosing rock may weigh the same.The magma cannot rise farther in this so-called neutral buoyancy position.Instead,it begins to build up its volume,stretching and inflating the crust in some areas and in other places passively filling the gaps opened by fractures in the earth that occur commonly in those regions where the crust is prone to movement.As the volume of magma increases,great pieces of surrounding rock may detach and settle into the molten chamber,a process called stoping.Small stoped pieces called xenoliths,meaning“foreign rocks,”may be smaller than a coin,whereas larger blocks may be the size of buildings. Some stoped blocks can drop hundreds of meters and partly or wholly melt within the magma,altering the magma chemistry in noticeable ways.Assimilation is the digestion of stoped blocks and surrounding solid rock by magma.Chemical studies show that only a small fraction of any typical magma body consists of assimilated material.The continuously cooling magma simply does not have enough heat to incorporate much new material after it stops rising in the shallow crust.

According to paragraph 4,all of the following are true of stoped rock pieces EXCEPT:

Negative Factual Information Questions否定事实信息题

AThey originate from the effect of magma on the surrounding solid rock.

BThey can be as large as buildings.

CThey can change the chemical composition of magma when they are assimilated.

DThey prevent magma in the shallow crust from rising further.

9

Magma is a mixture of molten (melted)and semi-molten rock and other solids found beneath Earth’s surface.[■]Melting in Earth requires very specific conditions:the pressure must be just low enough and the temperature just high enough for rock to melt. [■]For example,the center of Earth’s core,6,300 kilometers beneath the surface,is the hottest point in the planet,yet extremely high pressure prevents the solid metal of the inner core from melting. [■]The atoms that make up this metal simply cannot break their bonds to move randomly in a fluid state.[■]A little closer to Earth’s surface, though,the pressure drops and the still very hot outer portion of the core melts.In fact,Earth’s outer core is the largest magma chamber in the solar system.Fortunately for us,this magma is contained by the thick,strong shell of Earth’s crust and mantle-its solid outer layer and the somewhat more fluid layer immediately beneath it.

Look at the four squares [■] that indicate where the following sentence could be added to the passage

At certain pressures,even very high temperatures will not melt rock or metal.Insert Text Questions句子插入题

Where would the sentence best fit？Click on a square  sentence to the passage.

10

Magma forms when the pressure is just low enough and the temperature just high enough for rock to melt.

 

Prose Summary Questions概要小结题

 

Select 3 answers

APlates that move in response to the motion of Earth’s mantle create the temperature and pressure conditions necessary for magma to form.

BAs gabbroic and granitic magma rise from their places of origin,they create fractures in the surrounding solid rock that reduce the pressure on the overlying crust.

CWhen conditions stop magma from rising further,it increases in volume and takes in small and large pieces of the surrounding solid rock,resulting in changes in the magma’s chemistry.

DGabbroic magma,which forms when rising hot rock encounters pressures low enough for it to melt,supplies the heat that turns crustal rock into granitic magma.

EMagma makes up Earth’s outer core,but it also forms closer to the surface and rises at a rate determined by the difference in density between it and the surrounding solid rock.

FAs magma continues to cool in the shallow crust,it stops melting all the material it had assimilated from stoped blocks and the surrounding solid rock.