What about AD, BC, BCE and BP Ages?
Page 6 of 12 |
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Before we plot up real data to compare with the theoretical decay
curve, let's see how years are reported. Dates can be expressed as
AD, BC, BCE (before common era), and BP (before present). The accepted
way to represent C-14 ages is in terms of years BP, where the
year 1950 is used as the "present." (1950 is the date that
the calibration curves were established. It also predates atmospheric
testing of the atom bomb, which significantly upset C12/C14 ratios
in the following years.)
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| The time line on the right illustrates the relationship
between BP and AD or BC ages. Click on the image and drag back
and forth to study this relationship. |
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Below are descriptions of 6 samples, with known ages expressed as
either AD or BC (also called BCE). Convert these dates to BP dates
(using 1950 as "the present.") Also, convert the three estimates
of C-14 years in the second table to BP dates.
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| Some materials with known age |
BP Age |
| 1. |
Douglas Fir tree rings - excavated from a cave in Arizona.
Date: 577 ± 50 years AD |
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| 2. |
Wood from Egyptian coffin - from the Ptolemic period based
on style. Date: 200 ± 150 years BCE |
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| 3. |
Wood fragments from the floor of a palace in Syria - Syro-Hittite
period. Date: 675 ± 50 years BCE |
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| 4. |
Giant Sequoia tree rings from California. Date: 979 ±
52 years BCE |
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| 5. |
Cedar of Lebanon fragments from funeral boat of Egyptian
King Sesostris III. Date: 1843 ± 50 years BC |
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| 6. |
Wood from the tombs of Egyptian Kings Sneferu and Zoser.
Average Date: 2650 ± 75 years BCE |
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| Assuming this is 1999, convert these ages into
BP dates. Example: an article that's 1000 years old has a BP age of
951. [BP = Age - (Today -1950) = 1000-(1999-1950) = 951] |
| Age |
BP Date
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| 7. |
Wood from Bristlecone Pine of White Mountains, California.
Age 4731 ± 75 years |
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| 8. |
Pleistocene mammoth bone from La Brea Tar Pits of Los
Angeles, California. Age: 12,200 ± 35 years |
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| 9. |
Cottage roof timber from Ireland. Age: 906
± 35 years |
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