GEOG 205 - Final Exam – 163 Questions and
Answers
Can you explain why reversals in the Earth's magnetic field help us to date
ocean sediments? - - Paleomagnetic Dating - there are electric currents
running through earth's core, and as the earth rotates it creates a magnetic
field that goes out into space. Over history, the magnetic field has reversed
itself a few times. Small mineral particles will settle in a direction aligned
with the Earth's magnetic field as they deposit on the ocean floor; and stay
aligned in that manner unless disturbed (depending on settlement of
particles, we can determine at what time they were disturbed - epochs
reversed and not)
- What are the limitations of radiocarbon dating in terms of time and
material that can be dated? - - It can only go back about 50,000 years and it
can only date organic material.
- What is a half-life, and what is its significance in terms of ability to date
material? - - Half-life is the time it takes for half of the original value of a
radioactive element to decay. If you compare the presence of a radioactive
isotope (carbon-14) within a sample to its known abundance on Earth, and its
known half-life (its rate of decay), you can calculate the age of the sample.
- What is the age limit of radiocarbon dating and why does it have a limit? -
- Traditional radiocarbon dating is applied to organic remains between 500
and 50,000 years old. It has a dating limit because if the sample is extremely
old, there will be a tiny amount of carbon-14 left.
- How abundant is 14C relative to other carbon isotopes? - - o About 1 part
per trillion of Earth's natural carbon is C14
o 98.89% of all carbon on earth is Carbon-12
- How is 14C produced? - - Space is filled with cosmic rays penetrating the
upper layers of our earth's atmosphere. Atomic nuclei hit by these rays are
split into their components. These fragments, flying apart with high velocity,
collide with other nuclei. If a neutron hits a nitrogen nucleus, a proton will be
released by the nitrogen nucleus. Nitrogen becomes carbon - switch out a
proton for a neutron. Carbon-14 decays at a gradual but steady rate, over
thousands of years. Carbon-14 is distributed evenly in the atmosphere by
weather activity.
- Has the atmospheric concentration of 14C been constant? Why is this
critical in 14C- dating? - - The production of 14C has not been constant in
the atmosphere, but other dating methods have helped to determine how
the 14C concentration has changed with time.
, - How can the study of tree rings be used to calibrate (refine) the ages we
get from radiocarbon dating? - - If you have a radiocarbon measurement on
a sample, you can try to find a tree ring with the same proportion of
radiocarbon. Since the calendar age of the tree rings is known, this then tells
you the age of your sample.
- Why is the time span dateable by dendrochronology not limited to the age
of the oldest living tree? - - Because dendrochronology is specific to the tree
you are studying, not taking other tree abundances into consideration.
- Describe the nature of the geological time scale: What was its original
basis? - - These were originally based on the restricted presence of fossils
within different rock layers that could be correlated from site to site. The
earliest geological time scales simply used the order of rocks laid down in a
sedimentary rock sequence with the oldest at the bottom.
- How is geologic time subdivided? - - Subdivided in decreasing order of
scale from Eons (the largest subdivision of geological time), Eras, Periods,
Epochs, and finally to the smallest subdivision of time called Ages.
- What are the names and absolute times of the eras, periods and epochs? -
- o Cenozoic Era - most recent (about 65 million years)
o Quaternary Period - including two epochs
§ Pleistocene Epoch
§ Holocene Epoch
Put into perspective: the earth is about 4.5 billion years old, and the
Quaternary began only about 2.6 million years ago.
- What Epoch, Period and Era are we currently in? - - We live in Holocene
Epoch, of the Quaternary Period, in the Cenozoic Era
- What are the complications of fitting the "Anthropocene" into the geologic
time scale? - - o A time where humans have replaced nature as the
dominant environmental force on Earth, shaping ecology and geology - which
is sometimes questioned.
o There is a big debate about where the Anthropocene can be integrated into
the official Geologic Time Scale.
- What is the difference between weather and climate? - - o Weather - refers
to local conditions on the scale of minutes, hours, days (sometimes months
to years) you can have a particularly wet month, warm winter, or rainy
decade.
o Climate is an average of weather conditions over 30 years or more, and
can be assessed for a single location, large area, or globally.
, - Why are the poles colder than the rest of the earth? - - o The angle at of
incoming solar radiation hits them (high latitude = INDIRECT sunlight)
o They have higher albedo (snow and ice)
o They receive less radiation per square meter
- What causes seasons? - - The earth's spin axis is tilted (23.5 degrees) with
respect to its orbital plane. This is what causes the seasons. When the
earth's axis points towards the sun, it is summer for that hemisphere. When
the earth's axis points away, winter can be expected.
- What are the solstices? - - The time of the year when the difference
between the length of days and the length of nights is the largest. June (20
or 21) and December (21 or 22).
- In what form is the radiation incoming from the sun and in what form is it
re-radiated and why is it important to the Earth's climate? - - o Sunlight that
reaches Earth's surface and atmosphere is solar radiation and it is either
absorbed or reflected (dissufuse). Absorbed energy gets re-radiated the in
the form of infrared, also known as longwave radiation.
o Climate Impact: The more sunlight a surface absorbs, the warmer it gets,
and the more energy it re-radiates as heat, less sunlight vise-versa (impacts
climate of regions depending on sun exposure)
- Can you explain what controls the absorption and reflection of these two
forms of radiation? - - o Clouds can either contribute to the retention of heat
or play an opposite role by reflecting radiation.
o Albedo: the percentage of incoming radiation reflected (rather than
absorbed)
- Can you sketch Hadley cells and explain what happens to temperature and
precipitation of air masses as they move through these cells? - -
- Can you list 3 non-anthropogenic greenhouse gases besides CO2? - -
Water vapour, methane, nitrous oxide
- How is the heat redistributed around the Earth? - - - Winds and ocean
currents play a major role in moving the surplus heat from the equatorial
regions to the polar regions.
o The Coriolis Effect is responsible for influencing large slow-moving fluids,
global air and ocean currents.
- What is the difference between sensible and latent heat? - - o "Sensible
heat" = the product of temperature of the air and its specific heat in other
words "what you can sense"
o Latent Heat = as water freezes the temperature does not change, but
energy is lost.
Answers
Can you explain why reversals in the Earth's magnetic field help us to date
ocean sediments? - - Paleomagnetic Dating - there are electric currents
running through earth's core, and as the earth rotates it creates a magnetic
field that goes out into space. Over history, the magnetic field has reversed
itself a few times. Small mineral particles will settle in a direction aligned
with the Earth's magnetic field as they deposit on the ocean floor; and stay
aligned in that manner unless disturbed (depending on settlement of
particles, we can determine at what time they were disturbed - epochs
reversed and not)
- What are the limitations of radiocarbon dating in terms of time and
material that can be dated? - - It can only go back about 50,000 years and it
can only date organic material.
- What is a half-life, and what is its significance in terms of ability to date
material? - - Half-life is the time it takes for half of the original value of a
radioactive element to decay. If you compare the presence of a radioactive
isotope (carbon-14) within a sample to its known abundance on Earth, and its
known half-life (its rate of decay), you can calculate the age of the sample.
- What is the age limit of radiocarbon dating and why does it have a limit? -
- Traditional radiocarbon dating is applied to organic remains between 500
and 50,000 years old. It has a dating limit because if the sample is extremely
old, there will be a tiny amount of carbon-14 left.
- How abundant is 14C relative to other carbon isotopes? - - o About 1 part
per trillion of Earth's natural carbon is C14
o 98.89% of all carbon on earth is Carbon-12
- How is 14C produced? - - Space is filled with cosmic rays penetrating the
upper layers of our earth's atmosphere. Atomic nuclei hit by these rays are
split into their components. These fragments, flying apart with high velocity,
collide with other nuclei. If a neutron hits a nitrogen nucleus, a proton will be
released by the nitrogen nucleus. Nitrogen becomes carbon - switch out a
proton for a neutron. Carbon-14 decays at a gradual but steady rate, over
thousands of years. Carbon-14 is distributed evenly in the atmosphere by
weather activity.
- Has the atmospheric concentration of 14C been constant? Why is this
critical in 14C- dating? - - The production of 14C has not been constant in
the atmosphere, but other dating methods have helped to determine how
the 14C concentration has changed with time.
, - How can the study of tree rings be used to calibrate (refine) the ages we
get from radiocarbon dating? - - If you have a radiocarbon measurement on
a sample, you can try to find a tree ring with the same proportion of
radiocarbon. Since the calendar age of the tree rings is known, this then tells
you the age of your sample.
- Why is the time span dateable by dendrochronology not limited to the age
of the oldest living tree? - - Because dendrochronology is specific to the tree
you are studying, not taking other tree abundances into consideration.
- Describe the nature of the geological time scale: What was its original
basis? - - These were originally based on the restricted presence of fossils
within different rock layers that could be correlated from site to site. The
earliest geological time scales simply used the order of rocks laid down in a
sedimentary rock sequence with the oldest at the bottom.
- How is geologic time subdivided? - - Subdivided in decreasing order of
scale from Eons (the largest subdivision of geological time), Eras, Periods,
Epochs, and finally to the smallest subdivision of time called Ages.
- What are the names and absolute times of the eras, periods and epochs? -
- o Cenozoic Era - most recent (about 65 million years)
o Quaternary Period - including two epochs
§ Pleistocene Epoch
§ Holocene Epoch
Put into perspective: the earth is about 4.5 billion years old, and the
Quaternary began only about 2.6 million years ago.
- What Epoch, Period and Era are we currently in? - - We live in Holocene
Epoch, of the Quaternary Period, in the Cenozoic Era
- What are the complications of fitting the "Anthropocene" into the geologic
time scale? - - o A time where humans have replaced nature as the
dominant environmental force on Earth, shaping ecology and geology - which
is sometimes questioned.
o There is a big debate about where the Anthropocene can be integrated into
the official Geologic Time Scale.
- What is the difference between weather and climate? - - o Weather - refers
to local conditions on the scale of minutes, hours, days (sometimes months
to years) you can have a particularly wet month, warm winter, or rainy
decade.
o Climate is an average of weather conditions over 30 years or more, and
can be assessed for a single location, large area, or globally.
, - Why are the poles colder than the rest of the earth? - - o The angle at of
incoming solar radiation hits them (high latitude = INDIRECT sunlight)
o They have higher albedo (snow and ice)
o They receive less radiation per square meter
- What causes seasons? - - The earth's spin axis is tilted (23.5 degrees) with
respect to its orbital plane. This is what causes the seasons. When the
earth's axis points towards the sun, it is summer for that hemisphere. When
the earth's axis points away, winter can be expected.
- What are the solstices? - - The time of the year when the difference
between the length of days and the length of nights is the largest. June (20
or 21) and December (21 or 22).
- In what form is the radiation incoming from the sun and in what form is it
re-radiated and why is it important to the Earth's climate? - - o Sunlight that
reaches Earth's surface and atmosphere is solar radiation and it is either
absorbed or reflected (dissufuse). Absorbed energy gets re-radiated the in
the form of infrared, also known as longwave radiation.
o Climate Impact: The more sunlight a surface absorbs, the warmer it gets,
and the more energy it re-radiates as heat, less sunlight vise-versa (impacts
climate of regions depending on sun exposure)
- Can you explain what controls the absorption and reflection of these two
forms of radiation? - - o Clouds can either contribute to the retention of heat
or play an opposite role by reflecting radiation.
o Albedo: the percentage of incoming radiation reflected (rather than
absorbed)
- Can you sketch Hadley cells and explain what happens to temperature and
precipitation of air masses as they move through these cells? - -
- Can you list 3 non-anthropogenic greenhouse gases besides CO2? - -
Water vapour, methane, nitrous oxide
- How is the heat redistributed around the Earth? - - - Winds and ocean
currents play a major role in moving the surplus heat from the equatorial
regions to the polar regions.
o The Coriolis Effect is responsible for influencing large slow-moving fluids,
global air and ocean currents.
- What is the difference between sensible and latent heat? - - o "Sensible
heat" = the product of temperature of the air and its specific heat in other
words "what you can sense"
o Latent Heat = as water freezes the temperature does not change, but
energy is lost.
