NRM 140 EXAM #2 (Ch 5 & 6) QUESTIONS AND
ANSWERS 100% CORRECT
What information can we get from tree rings? How far back can tree ring dating take us? -
ANSWER Tree rings can tell precipitation patterns, temperature, indication of droughts and
fires, and ecosystem health. Tree ring dating can take us back to over 10,000 years ago.
What is the difference between an atom, an ion, and an element? - ANSWER An atom is the
smallest unit of matter, and has an equal number of protons and electrons.
An ion is an atom that has gained or lost one or more electrons, therefore there is not an
equal number or protons and electrons.
An element is a substance that cannot be chemically converted or broken down into a simpler
substance, and is composed of atoms.
Describe an isotope. What is the difference between a stable isotope and a radioisotope? List
the stable and unstable isotopes of carbon and oxygen - ANSWER An isotope is an element
with a differing neutron numbers.
A stable isotope does not change over time, while a radioisotope can randomly emit a
high-energy particle (neutron) or gamma ray, becoming a different element
, Stable carbon: 12C, 13C
Unstable carbon: 11C, 14C
Stable oxygen: 16O, 17O, 18O
Unstable oxygen: 11-15O, 19-28O
Explain the process of radiocarbon dating. What is a half-life? How far back can we reliably
date materials containing carbon? What radioisotopes can be used for longer time periods -
ANSWER Radiocarbon dating uses the decay of a radioactive isotope of carbon (14C) to
measure time and date objects containing carbon-bearing materials.
A half-life is the time it takes for 1/2 of a radioactive atom to decay.
We can reliably date materials containing carbon up to 60,000 years ago.
Radioisotopes that can be used for longer time periods are Zircon contains 238-U, which has a
half-life of 4.5 billion years. It can tell us when magma started cooling. This radioisotope
eventually decays to 208-Pb.Labradorite contains 40-K, which has a half-life of 1.25 billion
years. This radioisotope eventually decays to 40-Ar.
Explain the process of fractionation of oxygen isotopes as water evaporates from oceans and
condenses to form precipitation. Is glacial ice relatively rich or depleted in 18O compared to
sea-water? What happens to δ18O as latitude increase? - ANSWER Fractionation of oxygen
isotopes refers to a process of water evaporation. In a cold ocean, heavier water (18O) resists
evaporation when compared to lighter water (16O); but in a warm ocean, the evaporation of
ANSWERS 100% CORRECT
What information can we get from tree rings? How far back can tree ring dating take us? -
ANSWER Tree rings can tell precipitation patterns, temperature, indication of droughts and
fires, and ecosystem health. Tree ring dating can take us back to over 10,000 years ago.
What is the difference between an atom, an ion, and an element? - ANSWER An atom is the
smallest unit of matter, and has an equal number of protons and electrons.
An ion is an atom that has gained or lost one or more electrons, therefore there is not an
equal number or protons and electrons.
An element is a substance that cannot be chemically converted or broken down into a simpler
substance, and is composed of atoms.
Describe an isotope. What is the difference between a stable isotope and a radioisotope? List
the stable and unstable isotopes of carbon and oxygen - ANSWER An isotope is an element
with a differing neutron numbers.
A stable isotope does not change over time, while a radioisotope can randomly emit a
high-energy particle (neutron) or gamma ray, becoming a different element
, Stable carbon: 12C, 13C
Unstable carbon: 11C, 14C
Stable oxygen: 16O, 17O, 18O
Unstable oxygen: 11-15O, 19-28O
Explain the process of radiocarbon dating. What is a half-life? How far back can we reliably
date materials containing carbon? What radioisotopes can be used for longer time periods -
ANSWER Radiocarbon dating uses the decay of a radioactive isotope of carbon (14C) to
measure time and date objects containing carbon-bearing materials.
A half-life is the time it takes for 1/2 of a radioactive atom to decay.
We can reliably date materials containing carbon up to 60,000 years ago.
Radioisotopes that can be used for longer time periods are Zircon contains 238-U, which has a
half-life of 4.5 billion years. It can tell us when magma started cooling. This radioisotope
eventually decays to 208-Pb.Labradorite contains 40-K, which has a half-life of 1.25 billion
years. This radioisotope eventually decays to 40-Ar.
Explain the process of fractionation of oxygen isotopes as water evaporates from oceans and
condenses to form precipitation. Is glacial ice relatively rich or depleted in 18O compared to
sea-water? What happens to δ18O as latitude increase? - ANSWER Fractionation of oxygen
isotopes refers to a process of water evaporation. In a cold ocean, heavier water (18O) resists
evaporation when compared to lighter water (16O); but in a warm ocean, the evaporation of
