Earth's History - Fossil Record

Scientists determine the age of rocks and fossils using 2 different techniques. These techniques are called radioactive or absolute dating and (a)   dating.

Atoms are isotopes that have the same atomic (a)   but have different atomic masses.

The nuclei of some isotopes release particles or energy or both. What are these isotopes called?

(a)  

The amount of time it takes for 1/2 of a sample of isotope to decay is called the (a)   life.

When an organism dies the amount of _____________ remains constant over time.

• Carbon-14
• Carbon-12

When an organism dies the amount of ________________ continues to decay.

• Carbon-14
• Carbon-12

Carbon dating ____________ be used to date fossils older than 75,000 years old.

• can
• cannot

When a fossil is dated by measuring the amount of an isotope remaining, it is known as (a)   dating.

When a fossil is dated by comparing its placement with that of fossils in other layers of rock, it is known as (a)   dating.

Can a specimen be too old for Carbon dating? If so, what age and why?