Determining the Age of Rocks and Geological Events

Introduction

Scientists determine ages of rocks and geological events through methods involving numerical ages of rocks.
The Earth is calculated to be 4.55 billion years old.
Examples of ancient rocks:
- Metamorphic rock gneiss in Minnesota and Wisconsin (over a billion years old).
- Vishnu schist in the Grand Canyon (1.8 billion years old).

Discovery of radioactive decay helped estimate Earth's age.
Radioactive decay provides a timeline of geological events through mineral elements.

Elements have unique atomic numbers (e.g., Potassium: 19 protons, Uranium: 92 protons).
Isotopes: Versions of an element with varying neutron numbers.
Radioactive decay processes:
- Beta Decay: Isotope loses an electron, converting a neutron to a proton (e.g., Potassium-40 to Calcium).
- Electron Capture: Electron absorbed by nucleus, changing a proton to a neutron (e.g., Potassium to Argon).
- Alpha Decay: Alpha particle ejected, converting Uranium to Thorium, eventually forming stable lead isotopes.

Half-Life: Time for half of the parent isotope to convert to daughter isotope.
Analogy: Green candies (parent isotopes) convert to orange candies (daughter isotopes).
Graph representation:
- As time progresses, parent isotopes decrease while daughter isotopes increase.
- After two half-lives, parent isotopes reduce to a quarter of the original; after three, to an eighth.
- Predictable pattern in isotope ratios helps measure rock ages.

Accurate dating becomes challenging after many half-lives due to minimal parent isotopes.
Example calculation:
- Potassium-40 to Argon-40 half-life is 1.25 billion years.
- If two half-lives occur, rock age is 2.5 billion years.

Geologists use these processes to determine numerical ages of rocks, establishing timing of Earth's history events.
Assess confidence in understanding these methods and completing related tasks.