In an Unweathered Sample of Igneous Rock,the Ratio of an Unstable

question 27

Multiple Choice

In an unweathered sample of igneous rock,the ratio of an unstable isotope to its stable daughter isotope is 1:15.If no daughters were present at the time the rock cooled below closure temperature,and the half-life of the isotope is 50 million years,how old is the rock?

• A) 200 million years
• B) 400 million years
• C) 750 million years
• D) 1 billion years

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Definitions:

Frontal Lobe

One of the four major lobes of the cerebral cortex, associated with reasoning, planning, parts of speech, movement, emotions, and problem-solving abilities.

Hippocampus

A region of the brain that is associated with memory formation, organization, and storage.

Cerebellum

A region of the brain that plays an important role in motor control, coordination, precision, and accurate timing.

Decay Theory

A theory suggesting that memory fades and disappears over time if it is not accessed and used.