In 1938, sandals woven from strands of tree bark were found...

In 1938, sandals woven from strands of tree bark were found in Fort Rock Creek Cave in Oregon. The bark contained $34 \%$ of the level of ${ }^{14} \mathrm{C}$ found in living bark. Approximately how old were the sandals? [Note: This discovery by University of Oregon anthropologist Luther Cressman forced scientists to double their estimate of how long ago people came to the Pacific Northwest.]

Key Concepts

Archaeological Chronology

This concept involves establishing a timeline for past human activity and cultural evolution based on the dating of artifacts and remains. Techniques like radiocarbon dating are crucial for constructing accurate historical chronologies, thereby helping scientists understand the timing and sequence of events in human history.

Radiocarbon Dating

This is a scientific method used to determine the age of organic materials by measuring the remaining amount of carbon-14, a naturally occurring radioactive isotope. Since carbon-14 decays at a known rate, comparing the remaining levels in a sample to the levels in a living organism allows scientists to estimate when the sample ceased exchanging carbon with the atmosphere.

Half-Life

The half-life is the time required for half of the radioactive isotope in a sample to decay. For carbon-14, this period is approximately 5730 years. Understanding the half-life is essential for calculating the age of archaeological finds using radiocarbon dating.

Exponential Decay

Exponential decay describes the process by which the quantity of a radioactive substance decreases over time at a rate proportional to its current amount. This mathematical principle underlies the decay patterns observed in carbon-14, making it possible to relate the percentage of remaining carbon-14 in a sample to its age.

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