Sedimentary rocks

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Sedimentary rocks

by newton9 » Fri Jun 10, 2011 5:08 am
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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by gauravgundal » Fri Jun 10, 2011 5:41 am
IMO D

Question: Which answer choice would counter the claim that iridium rich layer is evidence for the meteorite collision theory
Geologist theorize that meteorite's collision resulted in a huge cloud of iridium laden dust and in the process of formation of sedimentary rock the settled dust formed a layer of iridium-rich rock.
assumption of geologist is that earth doesn't have enough of iridium material.

let see the answer choices
A. This doesn't refute the claim.
B. This may doubt the claim ,but possible not ..This can make us think that in those millions of years of process some another event lead to iridium rich rock/iridium on earth...(but this is a huge leap so don't mark it.)
C. Dates are not important for us
D. Yup..This makes sense.
E. This would support the theory.

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by M09 » Fri Jun 10, 2011 6:00 am
newton9 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.
IMO D
it gives an alternate explanation for the dust formation.

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by abhishek.pati » Fri Jun 10, 2011 8:54 am
IMO D

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by vishalkc2 » Fri Jun 10, 2011 10:16 am
IMO D

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by worldpeace93 » Mon Jun 13, 2011 10:45 pm
Answer D

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by sanabk » Tue Jun 14, 2011 11:09 am

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by ratan_2009 » Tue Jun 14, 2011 4:36 pm
D is the answer