The principle of superposition states:

• The oldest rocks are found at the top

• The youngest rocks are found at the bottom

• The oldest rocks are found at the bottom

• Rocks are always the same age

Which isotope is used to date organic remains up to ~50,000 years old?

• Potassium-40

• Carbon-14

• Uranium-235

• Lead-207

The time it takes for half of a radioactive isotope to decay is called:

• Decay period

• Half-life

• Radioactive age

• Isotope ratio

Which isotope ratio in ice cores is used as a climate proxy?

• O¹⁸ : O¹⁶

• C¹⁴ : N¹⁴

• K : Ar

• U : Pb

Which gas has the strongest correlation with global temperature in past climates?

• Oxygen

• Methane

• Carbon dioxide

• Argon

Explain the main difference between relative dating and absolute dating.

Why is radiometric dating more reliable than relative dating?

What do trapped gas bubbles in ice cores reveal about Earth’s past atmosphere?

Identify one limitation of using ice cores as evidence of past climates.

How can fossils help reconstruct past ecosystems?