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

question 45

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

---

Definitions:

Remote Past

A period referring to the distant historical past, signifying times or events significantly far back from the current period.

Systematic Desensitization

A therapeutic technique used to reduce phobia or anxiety through gradual exposure to the feared object or situation combined with relaxation exercises.

Stimulant Drugs

Substances that increase alertness, attention, and energy by enhancing the activity of certain neurotransmitters in the brain.

Electroshock Therapy

A psychiatric treatment in which seizures are electrically induced in patients to provide relief from mental disorders, more commonly known as Electroconvulsive Therapy (ECT).