PRO

Where Your Ideas can change Minds

Please visit our new forum at

http://www.4forums.com

CON


YouDebate.com Forum
» back to YouDebate.com
Register | Profile | Log In | Lost Password | Active Users | Help | Board Rules | Search | FAQ |
Custom Search
» You are not logged in.   log in | register

  YouDebate.com Forum
   Science Debates
     Dating rock layers
       Dating rock layers

Topic Jump
« Back | Next »
[ Single page for this topic ]
Forum moderated by: admin
    

    
Gomez

|     |       Report Post



Junior Member
Post Score
Adjustment:
n/a

Rate this post:

How are layers of sedimentary rock dated?
 


Posts: 20 | Posted: 04:31 AM on January 13, 2006 | IP
RoyLennigan

|        |       Report Post



Regular
Post Score
Adjustment:
n/a

Rate this post:

its really not any different than dating other rock types.  this site should exlpain how its done:
http://en.wikipedia.org/wiki/Rock_dating
 


Posts: 152 | Posted: 12:30 PM on January 16, 2006 | IP
Gomez

|     |       Report Post



Junior Member
Post Score
Adjustment:
n/a

Rate this post:

Thanks but that only says how old the rocks themselves are not how long they have been in that layer. My birth certificate shows how old I am but not how long I have lived in my current home.
 


Posts: 20 | Posted: 04:25 AM on January 17, 2006 | IP
RoyLennigan

|        |       Report Post



Regular
Post Score
Adjustment:
n/a

Rate this post:

Quote from Gomez at 04:25 AM on January 17, 2006 :
Thanks but that only says how old the rocks themselves are not how long they have been in that layer. My birth certificate shows how old I am but not how long I have lived in my current home.



i'm not too sure what you mean about how long its been in that layer.  once the rock is formed, it usually stays there.  geological processes bend and reform the layers, but usually you can see where they are seperated.  geologists figure out the dates of the surrounding rock in different layers as well as the one they are working on to get an idea of the timeline of the area.  the rocks make up the layer, so they have been in that layer as long as they have been rocks, unless they were tossed around by a glacier, or some other powerful geological process.
 


Posts: 152 | Posted: 07:28 AM on January 17, 2006 | IP
Nuno

|     |       Report Post



Junior Member
Post Score
Adjustment:
n/a

Rate this post:

The earth's crust is mostly sedimentary rock which is laid down by water or wind. Both media move the sediment from one place to another. A bad flood in England a few years ago left a village under a layer of mud that had washed down from the hills. Radio-dating would be unable to say how long that layer had been there.
 


Posts: 20 | Posted: 1:35 PM on January 17, 2006 | IP
RoyLennigan

|        |       Report Post



Regular
Post Score
Adjustment:
n/a

Rate this post:

Quote from Nuno at 1:35 PM on January 17, 2006 :
The earth's crust is mostly sedimentary rock which is laid down by water or wind. Both media move the sediment from one place to another. A bad flood in England a few years ago left a village under a layer of mud that had washed down from the hills. Radio-dating would be unable to say how long that layer had been there.



no, they would be able to determine the age.  rocks are put down in layers, bit by bit.  geologists compare the layers to determine the age and where it lines up with what was going on at the time.  for instance, they can use a layer of sulfer, or some chemical known to be associated with a volcano eruption, and compare it to a layer of rock to show where in the timeline a certain nearby volcano erupted.  or if they determine the age of igneous rocks from the volcano and use that as a constant for the age of the layer they are examining, they can determine the age of that layer.  also, these are not exact dates,  they might be off a bit.

"The precision of a method of dating depends in part on the half-life of the radioactive isotope involved. For instance, carbon-14 has a half-life of less than 6000 years. After an organism has been dead for 60,000 years, so little carbon-14 is left in it that accurate dating becomes impossible. On the other hand, the concentration of carbon-14 falls off so steeply that the age of relatively young remains can be determined precisely to within a few decades. The isotope used in uranium-thorium dating has a longer half-life, but other factors make it more accurate than radiocarbon dating."

[On uranium-lead dating]"One of its great advantages is that any sample provides two clocks, one based on uranium-235's decay to lead-207 with a half-life of about 700 million years, and one based on uranium-238's decay to lead-206 with a half-life of about 4.5 billion years, providing a built-in crosscheck that allows accurate determination of the age of the sample even if some of the lead has been lost."
 


Posts: 152 | Posted: 5:45 PM on January 17, 2006 | IP
Nuno

|     |       Report Post



Junior Member
Post Score
Adjustment:
n/a

Rate this post:

Wouldn't volcanic eruptionsonly be any good for setting the age of a rock layer if there were eruptions in that area?

(Edited by Nuno 1/17/2006 at 6:14 PM).
 


Posts: 20 | Posted: 6:08 PM on January 17, 2006 | IP
RoyLennigan

|        |       Report Post



Regular
Post Score
Adjustment:
n/a

Rate this post:

Quote from Nuno at 6:08 PM on January 17, 2006 :
Wouldn't volcanic eruptionsonly be any good for setting the age of a rock layer if there were eruptions in that area?

(Edited by Nuno 1/17/2006 at 6:14 PM).


yeah but the same method can be used with any major geological process/natural catastrophe that deposits unique minerals, or deposits normal minerals in an abnormal way (like too much at once).  geology is a really fascinating subject.  its like the forensics of the earth.

also, in the history of the earth, there have been many times in which one volcano eruption or one asteroid hitting the earth has been so powerful that it caused a unique layer to form all over the world.



(Edited by RoyLennigan 1/17/2006 at 10:19 PM).
 


Posts: 152 | Posted: 10:18 PM on January 17, 2006 | IP
Gomez

|     |       Report Post



Junior Member
Post Score
Adjustment:
n/a

Rate this post:

Thanks, dood. It could also be possible that water movements carried the volcanic stuff somewhere else.

(Edited by Gomez 1/18/2006 at 08:18 AM).
 


Posts: 20 | Posted: 04:38 AM on January 18, 2006 | IP
RoyLennigan

|        |       Report Post



Regular
Post Score
Adjustment:
n/a

Rate this post:

Quote from Gomez at 04:38 AM on January 18, 2006 :
Thanks, dood. It could also be possible that water movements carried the volcanic stuff somewhere else.

(Edited by Gomez 1/18/2006 at 08:18 AM).



yes it is, but then they would be eroded much more rapidly and soon turn into many tiny pieces of sedimentary rock.  but there are instances of huge boulders being tossed around by huge floods and glaciers (especially in the western-northwestern US).  they're still around in that form today, seemingly random boulders sitting on gentle hills.
 


Posts: 152 | Posted: 09:07 AM on January 18, 2006 | IP
Nuno

|     |       Report Post



Junior Member
Post Score
Adjustment:
n/a

Rate this post:

That would go along with the all eroded canyons that are found in North America. The Earth must have been badly traumatised.
 


Posts: 20 | Posted: 4:59 PM on January 18, 2006 | IP
Gomez

|     |       Report Post



Junior Member
Post Score
Adjustment:
n/a

Rate this post:

Science magazine reported in 1970 that the same sample of moon  rock was dated eight times and the eight results differed by sixteen billion years. With that much room for error how do they double check the radio dates to make sure the right ones are found?

(Edited by Gomez 3/8/2006 at 06:25 AM).
 


Posts: 20 | Posted: 06:22 AM on March 8, 2006 | IP
hatfield

|     |       Report Post



Junior Member
Post Score
Adjustment:
n/a

Rate this post:

The only way to check the dates is against a date known by another method. Carbon dates can be checked against anything with a historical age and so its accuracy is only known up to a few 1000 years. Rock dating is checked by the known ages of fossils. We know their ages by the layers of rock they are found in.
 


Posts: 21 | Posted: 06:36 AM on March 8, 2006 | IP
SilverStar

|        |       Report Post




Junkie
Post Score
Adjustment:
n/a

Rate this post:

By the fossils found in them. Incidently the deturmin the age of the fossils found in them by the layer that their in.


-------
Darkside Enterprises were the impossible meets possible.

Tread softy and carry a big stick, preferably an AT4
 


Posts: 681 | Posted: 10:54 PM on May 4, 2007 | IP
Apoapsis

|     |       Report Post



Fanatic
Post Score
Adjustment:
n/a

Rate this post:

Quote from Gomez at 05:22 AM on March 8, 2006 :
Science magazine reported in 1970 that the same sample of moon  rock was dated eight times and the eight results differed by sixteen billion years. With that much room for error how do they double check the radio dates to make sure the right ones are found?

(Edited by Gomez 3/8/2006 at 06:25 AM).



Do you have a reference for this that might give this claim any validity?  

Or is it from a creationist web site?

Did you READ this article?


-------
Pogge:” This is the volume of a sphere with a 62 kilometer (about 39 miles) radius, which is considerably smaller than the 2,000 mile radius of the Earth.”
Wikipedia:” For Earth, the mean radius is 6,371.009 km(≈3,958.761 mi; ≈3,440.069 nmi).”
Wisp to Lester (on Pogge): Do you admit he was wrong about the basics?
Lester: No

 


Posts: 1747 | Posted: 11:28 PM on April 30, 2008 | IP
ImaAtheistNow

|      |       Report Post



Member
Post Score
Adjustment:
n/a

Rate this post:

Quote from SilverStar at 10:54 PM on May 4, 2007 :
By the fossils found in them. Incidently the deturmin the age of the fossils found in them by the layer that their in.


Another half-truth from the ignorant, anti-science crowd.

What you mentioned is called relative dating.  Which, by the way, was devised by Bible-believing scientists, before Darwin's "The Origin of Species" was published.

Absolute ages are determined by radiometric dating.  As science has progressed over the last about century, the methods used in radiometric dating have become better and better: isochrons being one such excellent method.  

Contra what was implied elsewhere in this thread, the age of the moon - as well as the age of meteorites and the earth - has been well establised using radiometric methods.


The Earth Itself
For various reasons such as erosion and volcanism, only very little of the rocks that formed some of earth’s original surface are available to be dated. Some rocks of great antiquity, such as those of the North Atlantic Craton, have been dated.  

13 samples of Amitsoq gneisses from Isua in western Greenland were dated using a Rb-Sr isochron: the result was 3.64 (+/- 0.06) billion years old (1 billion years = 1 Giga-annum, or simply 1 Ga).  Some of these samples were also subjected to the Pb-Pb technique, yielding an age of 3.74 (+/- 0.12) Ga. (Dalrymple 141, 147-151).

Moon Rocks
Unlike the Earth, the Moon is geologically and meteorologically dead.  Thus, its surface preserves rocks of greater age.

Radiometric dating of the oldest lunar rocks available produced ages in excess of 4.3 Ga.  For example, using the Rb-Sr isochron technique to date Apollo 17’s samples numbered 77215, 72417, and 76535 gave ages of 4.33 (+/- 0.04), 4.47 (+/- 0.10), and 4.51 (+/- 0.07) Ga, respectively.  Further, sample 77215 was also dated using an Sm-Nd isochron for which an age of 4.37 (+/- 0.07) Ga was obtained (Dalrymple 238-250).

Meteorites
By 1991, over 40 different meteorites had been dated to between 4.4 and 4.6 Ga using Rb-Sr or Sm-Nd isochrons, or 40Ar/39Ar age spectra. As one example, the chondrite St. Severin was dated using all three above methods: the weighted average was 4.41 Ga (Dalrymple 286-290).  

One study of 38 different chondrites, using the Rb-Sr method, produced a single, tightly collinear isochron for all samples, indicating the same age of 4.498 (+/- 0.015) Ga for the entire set (Dalrymple 293-294).


Reference

Dalrymple, G. Brent. The Age of the Earth. Stanford: Stanford University Press, 1991.

 


Posts: 43 | Posted: 6:42 PM on October 12, 2008 | IP
    
[ Single page for this topic ]

Topic Jump
« Back | Next »
[ Single page for this topic ]
Forum moderated by: admin
    

Topic options: Lock topic | Unlock topic | Make Topic Sticky | Remove Sticky | Delete thread | Move thread | Merge thread

 

© YouDebate.com
Powered by: ScareCrow version 2.12
© 2001 Jonathan Bravata. All rights reserved.