# Question: What is half life and how is it used in absolute dating?

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The half-life is constant and measurable for a given radioactive isotope, so it can be used to calculate the age of a rock. For example, the half-life uranium-238 (238U) is 4.5 billion years and the half-life of 14C is 5,730 years. The principles behind this dating method require two key assumptions.

## How do we use half-life to find absolute age?

To determine the absolute age of this mineral sample, we simply multiply y (=0.518) times the half life of the parent atom (=2.7 million years). Thus, the absolute age of sample = y * half-life = 0.518 * 2.7 million years = 1.40 million years.

## What is half-life in absolute age?

A half-life is the time it takes for half a given amount of an isotope to decay. Radiometric dating uses the rate of decay of unstable isotopes to estimate the absolute ages of fossils and rocks. Carbon-14 can be used to date recent organic remains.

## Can fossils be found in lava?

Most organisms never become fossils, but instead decompose after death, and any hard parts are broken into tiny fragments. Igneous rocks, which form from cooling magma or lava, and metamorphic rocks, which have been altered by heat and pressure, are unlikely to contain fossils (but may, under special circumstances).

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