Who expanded on James Hutton’s concept of uniformitarianism and argued for a much older Earth?
Charles Lyell
Why did Charles Darwin believe the Earth had to be very old?
To allow enough time for evolution to occur as recorded in the fossil record.
What three arguments did Lord Kelvin use to argue for a younger Earth?
- Sun’s energy limited to ~20 million years; 2. Cooling Earth calculations (20–100 million years); 3. Tidal friction slowing Earth’s rotation.
Who discovered spontaneous radiation?
Henri Becquerel
Who were the Curie family and what did they contribute?
Pierre and Marie Curie discovered radium and polonium, studied radiation, and shared a Nobel Prize with Becquerel.
What everyday products was radium once used in?
Watch dials, toy chemistry sets, water, makeup, cooking utensils, milk, and virility products.
What are the three main particles of an atom’s nucleus?
Protons (+), Neutrons (0), and Electrons (-) orbiting outside.
What are isotopes?
Atoms of the same element with the same number of protons but different atomic masses due to varying neutrons.
What happens when a nucleus has too many neutrons?
It becomes unstable and undergoes radioactive decay, releasing alpha, beta, or gamma radiation.
What is half-life?
The time required for half of a radioactive isotope to decay into its daughter element.
What is the half-life of Carbon-14?
5,740 years
Why isn’t Carbon-14 used to date the Earth?
Because after ~50,000 years there isn’t enough C14 left to measure.
Which isotopes are used for dating very old rocks?
Potassium-40, Rubidium-87, Uranium-238, and Uranium-235.
What does alpha decay release?
2 protons and 2 neutrons (a helium atom).
What discovery overturned Lord Kelvin’s cooling Earth argument?
Radioactive decay provided a constant heat source, allowing for a much older Earth.
What did early radioactive dating reveal about Earth’s age?
That Earth is billions of years old.
What is the significance of isotopes in geology?
They act as a clock to determine the absolute ages of rocks.
What does the modern geologic time scale show?
It divides Earth’s history into eons, eras, periods, epochs, and ages with absolute numeric ages.
