Question

The age of most ancient geological formations is estimated by (a) potassium-argon method (b) carbon- 14 dating method (c) radium-silicon method (d) uranium-lead method

Short answer

(d) uranium-lead method

Step-by-step solution

Understand the Methods

We need to understand each dating method mentioned. The "potassium-argon method" is used to date volcanic rocks and ash and is suitable for dating materials over 100,000 years old. The "carbon-14 dating method" is for dating organic material and is effective for samples up to about 50,000 years old. The "radium-silicon method" does not exist in common geological dating. The "uranium-lead method" is used to date the age of the Earth and the most ancient rocks, and it is effective for samples that are billions of years old.

Identify the Target Age

The question asks about the most ancient geological formations, which would be rocks that are millions or even billions of years old. We need a method that can accurately date such old formations.

Match the Method to the Age

Based on the understanding from Step 1, the "uranium-lead method" is the most suitable for estimating the age of ancient geological formations because it can date formations that are billions of years old, unlike the other methods which are for much more recent or different materials. Therefore, the uranium-lead method is the best choice for dating ancient geological formations.

Key concepts

Uranium-Lead Dating

Uranium-Lead Dating is one of the most reliable methods used to determine the age of the Earth and ancient geological formations. This method makes use of the decay of uranium isotopes into lead isotopes. Specifically, uranium-238 decays to lead-206, and uranium-235 decays to lead-207. This dual decay process acts like a time capsule, allowing scientists to accurately date samples that are millions to billions of years old.

The reason uranium-lead dating is so precise is because it utilizes two independent decay chains, and the comparison of both decay systems helps cross-verify the results. This process is usually performed on minerals like zircon, which can trap uranium when they form but reject lead, ensuring the lead present is from the decay of uranium.

• Suitable for dating rocks older than 1 million years
• Effective on igneous and metamorphic rocks
• Two decay systems provide cross-checking capability

Thus, uranium-lead dating is a cornerstone in geology, giving us insight into Earth’s earliest periods.

Potassium-Argon Dating

Potassium-Argon Dating is an essential tool for dating volcanic rocks and ash. The method is based on the radioactive decay of potassium-40 to argon-40. What makes this technique particularly useful is that potassium is a common element in many minerals, making the method widely applicable.

This dating method is also reliable because argon, being a noble gas, does not typically form bonds with other elements and escapes from molten rock. This means any argon in the mineral was most likely formed from the radioactive decay of potassium-40, allowing accurate dating of the rock.

• Ideal for samples older than 100,000 years
• Commonly used in volcanic materials
• Unleashes the potential to study well-preserved volcanic sequences

Consequently, potassium-argon dating is a fundamental method to construct geological timescales, especially in studying Earth's volcanic activity.

Carbon-14 Dating

Carbon-14 Dating, or radiocarbon dating, is central in studying biological artifacts and historical remains. This technique is based on the decay of the radioactive isotope carbon-14, which is naturally created in the atmosphere and absorbed by living organisms.

When an organism dies, it stops absorbing carbon-14, and the existing carbon-14 in its body begins to decay into nitrogen-14. By measuring the remaining carbon-14, scientists can determine how long it has been since the organism's death.

• Effective for organic materials like wood, bone, and shells
• Suited for ages up to about 50,000 years
• Key for archaeology and understanding past climates

Carbon-14 dating is a revolutionary method, offering insights into human history and ecological changes through time.