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Sedimentary rock hardens within the earth's crust

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Sedimentary rock hardens within the earth's crust [#permalink]

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New post 05 Apr 2015, 08:17
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Sedimentary rock hardens within the earth's crust as lavers of matter accumulate and the pressure of the layers above converts the layers below into rock. One particular layer of sedimentary rock that contains an unusual amount of the element iridium has been presented as support for a theory that a meteorite collided with the earth some sixty million years ago. Meteorites are rich in iridium compared to the earth's crust, and geologists theorize that a meteorite's collision with the earth raised a huge cloud of iridium-laden dust. The dust, they say, eventually settled to earth where it combined with other matter, and as new layers accumulated above it, it formed a layer of iridium-rich rock.

Which one of the following, if true, would counter the claim that the iridium-rich layer described in the passage is evidence for the meteorite collision theory?

(A) The huge dust clo8ud described in the passage would have blocked the transmission of sunlight and lowered the earth's temperature.

(B) A layer of sedimentary rock takes millions of years to harden.

(C) Layers of sedimentary rock are used to determine the dates of prehistoric events whether or not they contain iridium.

(D) Sixty million years ago there was a surge in volcanic activity in which the matter spewed from the volcanoes formed huge iridium-rich dust clouds.

(E) The iridium deposit occurred at about the same time that many animal species became extinct and some scientists have theorized that mass dinosaur extinctions were caused by a meteorite collision.

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Re: Sedimentary rock hardens within the earth's crust [#permalink]

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New post 22 May 2015, 03:17
did not read the word counter and marked E :(
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Re: Sedimentary rock hardens within the earth's crust [#permalink]

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New post 22 May 2015, 15:14
adityadon wrote:
did not read the word counter and marked E :(


what do you mean by word counter?
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Re: Sedimentary rock hardens within the earth's crust [#permalink]

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New post 22 May 2015, 22:24
Nothing more joyous then marking first question of your day as correct!

D It is
As it suggests an alternative due to which iridium rich rocks could be created
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Re: Sedimentary rock hardens within the earth's crust [#permalink]

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New post 06 Sep 2015, 23:21
It is a weakening question.

X caused Y in the passage, however Z caused the X

X: a meteorite's collision with the earth
Y: a huge cloud of iridium-laden dust
Z: a surge in volcanic activity in which the matter spewed from the volcanoes
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Re: Sedimentary rock hardens within the earth's crust [#permalink]

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souvik101990 wrote:
Sedimentary rock hardens within the earth's crust as lavers of matter accumulate and the pressure of the layers above converts the layers below into rock. One particular layer of sedimentary rock that contains an unusual amount of the element iridium has been presented as support for a theory that a meteorite collided with the earth some sixty million years ago. Meteorites are rich in iridium compared to the earth's crust, and geologists theorize that a meteorite's collision with the earth raised a huge cloud of iridium-laden dust. The dust, they say, eventually settled to earth where it combined with other matter, and as new layers accumulated above it, it formed a layer of iridium-rich rock.

Which one of the following, if true, would counter the claim that the iridium-rich layer described in the passage is evidence for the meteorite collision theory?

(A) The huge dust clo8ud described in the passage would have blocked the transmission of sunlight and lowered the earth's temperature.

(B) A layer of sedimentary rock takes millions of years to harden.

(C) Layers of sedimentary rock are used to determine the dates of prehistoric events whether or not they contain iridium.

(D) Sixty million years ago there was a surge in volcanic activity in which the matter spewed from the volcanoes formed huge iridium-rich dust clouds.

(E) The iridium deposit occurred at about the same time that many animal species became extinct and some scientists have theorized that mass dinosaur extinctions were caused by a meteorite collision.


--Meteorites are rich in iridium in comparison to the Earth's crust
---One layer of sedimentary rock contains an unusual amount of iridium
---A meteorite caused this iridium (meteorite collision theory)

The main key to this question is understanding the conclusion. "It was a meteorite!" the conclusion says. How can we weaken this? Pretty easily actually. All we have to do is show that it was actually something else that caused this "huge cloud of iridium-laden dust" to form the layer of iridium-rich rock.

(A) This just talks more about the huge dust cloud. We don't want to know what effect the dust cloud had; we want to know what caused the dust cloud to begin with.

(B) But does this mean that it was/wasn't the meteorite that caused the iridium in the dust cloud? We don't know! All we know is that rock takes millions of years to harden. Okay....

(C) This functions much like (A). We don't care about any effects of the rock. AKA, we don't care how sedimentary rock is used. We care about what caused the iridium in the sedimentary rock.

(D) This looks great! (D) basically says, "nope. It wasn't the meteorite that caused the iridium. It was actually the matter spewed from the volcanoes." In other words, this provides an alternate cause and that is exactly what we wanted to do!

(E) This actually strengthens the conclusion! It does so by giving more credence to the idea that it was a meteorite that caused the iridium dust. Why? Well it says that the iridium formed at about the same time as mass dinosaur extinctions. So what? This is important because many people believe that the dinosaurs were extinct because of, you guessed it...a meteorite! While it doesn't conclusively prove that a meteorite caused the iridium in the rock. It shows that it seems to be correlated with another event that involved a meteorite. Hmm.... Either way, this definitely does not weaken the argument.
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Sedimentary rock hardens within the earth's crust [#permalink]

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New post 26 Jan 2018, 12:31
ManasviHP wrote:
Sedimentary rock hardens within the earth's crust as layers of matter accumulate and the pressure of the layers above converts the layers below into rock. One particular layer of sedimentary rock that contains an unusual amount of the element iridium has been presented as support for a theory that a meteorite collided with the earth some sixty million years ago. Meteorites are rich in iridium compared to the earth's crust, and geologists theorize that a meteorite's collision with the earth raised a huge cloud of iridium-laden dust. The dust, they say, eventually settled to earth where it combined with other matter, and as new layers accumulated above it, it formed a layer of iridium-rich rock.

Which one of the following, if true, would counter the claim that the iridium-rich layer described in the passage is evidence for the meteorite collision theory?

(A) The huge dust clo8ud described in the passage would have blocked the transmission of sunlight and lowered the earth's temperature.

(B) A layer of sedimentary rock takes millions of years to harden.

(C) Layers of sedimentary rock are used to determine the dates of prehistoric events whether or not they contain iridium.

(D) Sixty million years ago there was a surge in volcanic activity in which the matter spewed from the volcanoes formed huge iridium-rich dust clouds.

(E) The iridium deposit occurred at about the same time that many animal species became extinct and some scientists have theorized that mass dinosaur extinctions were caused by a meteorite collision.

Source: LSAT


Since we have to counter the claim, we need to provide an alternate reasoning that the
iridium-rich dust clouds were not casued by the meteorite collision but by something else

Option D(Sixty million years ago there was a surge in volcanic activity in which the matter
spewed from the volcanoes formed huge iridium-rich dust clouds)
gives us that reason to prove
that the iridium rich dust clouds which settled on the sedimentary rock did not occur due
to the meteorite collision.
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Re: Sedimentary rock hardens within the earth's crust [#permalink]

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New post 26 Jan 2018, 20:42
Skywalker18 wrote:
souvik101990 wrote:
Sedimentary rock hardens within the earth's crust as lavers of matter accumulate and the pressure of the layers above converts the layers below into rock. One particular layer of sedimentary rock that contains an unusual amount of the element iridium has been presented as support for a theory that a meteorite collided with the earth some sixty million years ago. Meteorites are rich in iridium compared to the earth's crust, and geologists theorize that a meteorite's collision with the earth raised a huge cloud of iridium-laden dust. The dust, they say, eventually settled to earth where it combined with other matter, and as new layers accumulated above it, it formed a layer of iridium-rich rock.

Which one of the following, if true, would counter the claim that the iridium-rich layer described in the passage is evidence for the meteorite collision theory?

(A) The huge dust clo8ud described in the passage would have blocked the transmission of sunlight and lowered the earth's temperature.

(B) A layer of sedimentary rock takes millions of years to harden.

(C) Layers of sedimentary rock are used to determine the dates of prehistoric events whether or not they contain iridium.

(D) Sixty million years ago there was a surge in volcanic activity in which the matter spewed from the volcanoes formed huge iridium-rich dust clouds.

(E) The iridium deposit occurred at about the same time that many animal species became extinct and some scientists have theorized that mass dinosaur extinctions were caused by a meteorite collision.


--Meteorites are rich in iridium in comparison to the Earth's crust
---One layer of sedimentary rock contains an unusual amount of iridium
---A meteorite caused this iridium (meteorite collision theory)

The main key to this question is understanding the conclusion. "It was a meteorite!" the conclusion says. How can we weaken this? Pretty easily actually. All we have to do is show that it was actually something else that caused this "huge cloud of iridium-laden dust" to form the layer of iridium-rich rock.

(A) This just talks more about the huge dust cloud. We don't want to know what effect the dust cloud had; we want to know what caused the dust cloud to begin with.

(B) But does this mean that it was/wasn't the meteorite that caused the iridium in the dust cloud? We don't know! All we know is that rock takes millions of years to harden. Okay....

(C) This functions much like (A). We don't care about any effects of the rock. AKA, we don't care how sedimentary rock is used. We care about what caused the iridium in the sedimentary rock.

(D) This looks great! (D) basically says, "nope. It wasn't the meteorite that caused the iridium. It was actually the matter spewed from the volcanoes." In other words, this provides an alternate cause and that is exactly what we wanted to do!

(E) This actually strengthens the conclusion! It does so by giving more credence to the idea that it was a meteorite that caused the iridium dust. Why? Well it says that the iridium formed at about the same time as mass dinosaur extinctions. So what? This is important because many people believe that the dinosaurs were extinct because of, you guessed it...a meteorite! While it doesn't conclusively prove that a meteorite caused the iridium in the rock. It shows that it seems to be correlated with another event that involved a meteorite. Hmm.... Either way, this definitely does not weaken the argument.
Great answer! I think this will suffice for anyone who has a doubt with this question

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Re: Sedimentary rock hardens within the earth's crust   [#permalink] 26 Jan 2018, 20:42
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