The Need for Conceptual Approaches to Understanding Change through Time
NUHFER, Edward, Geosciences and Center for Teaching and Learning
Idaho State University, Campus Box 8010, Pocatello, ID 83201, [email protected]
Concept - Relation of human existence to deep time. Teaching method- storytelling
ABSTRACT. Science involves study of the physical world: matter, energy, and time. A primary
contribution to science by geologists involves the understanding of change through time. Yet,
introductory textbooks and traditional instruction impart factual knowledge (age of Earth and
presentation of the Geologic Time Scale) rather than promote conceptual understanding. Introductory
students arrive with limited, self-made common-sense interpretations about change through time, and
most are dead wrong. Ability of students to comprehend the planet, their environment, and their place
and role in these in ways that are useful to their own lives requires more than recognizing that Earth is
old; it requires students to develop sophisticated, conceptualized thinking about time. The study of the
discovery of deep time is a marvelous topic to allow students to comprehend science as a way of
understanding the physical world through two major methods: repeated experimentation and
historical/multiple working hypotheses. Texts and instructors should work to convey deeper conceptual
understanding of change through time—not as merely age and ordered events— but also as patterns,
rates, magnitudes, durations and frequencies. Questions of great importance include the following. (1)
How do we understand change through time? (2) What are the patterns, rates, magnitudes, durations
and frequencies of a given process? (3) What variations are reasonably expected? (4) How do the
changes we see now compare to those we deduce from the past? (5) How do changes caused by
human activity compare with natural changes that would occur without such activity, and what are the
consequences of such change? This poster will show methods and exercises for promoting such
conceptual learning.
Learning to perceive change through time.
A Grave Problem
1. Visit any graveyard in the area: select three different headstones, and include in your selection a span
of dates that go back 70 or more years. Identify the rock type; look closely at the stone, and relate what
you notice to the weathering (Chapter 6) of your text. You can do this in pairs or groups, but the ground
rule is that everyone makes the visit and everyone contributes to the observations. Some cultures find it
bad taste to visit graveyards. If yours falls into that category, use dated cornerstones of buildings in the
downtown area instead to accomplish the same. There are plenty of old structures in Pocatello. After
having actually seen weathering of rock yourselves, decide which statement below best fits your
observed evidence.
(A) In general, the land wears away at the rate of about 1mm/yr.
(B) In general, the land wears away at the rate of about 1mm/decade.
(C) In general, the land wears away at the rate of about 1mm/century
(D) In general, the land wears away at the rate of about 1mm/1000 yrs.
Are the above hypotheses? If so, what method(s) of science are you employing?
2. Go to the web and use Alta Vista Search engine. Look up “erosion rates” and see if a reference
substantiates your rate observation. Bring report—one or two sentences back to class.
3. (Done a week later) Gather into groups of four and share graveyard observations and come up with
best rate estimate. Briefly, describe what you found to your three other members in the group. What
evidence of weathering did you discover?
4. (Following Class Period) Use your best estimate of rates derived from your work above to answer
two questions:
(A) Pocatello is about 4400 ft above seal level. Use your rate to calculate how long it would take to
erode this area to sea level.
(B) Let’s consider a magnificent gravestone marker about ten feet high. Use your rate to calculate
about how many years it will take to remove it.
5. (Next Following Class Period) To answer “A” and “B” above consider that the Earth is 4.6 billion
years old. What percent of geologic time is spent in removing Pocatello and the gravestone? Next,
frame 4.6 billion years in terms of a 24-hour day. In that context, how much of that 24-hour day would
be consumed during removal of Pocatello and the gravestone?
Patterns in Time
Can experiential learning
extend limits?
Laymen who evaluate their
lives over years spent in their
geological environment often
report perceptions of
comforting stability and
permanence. The landscape
seems familiar; hills, valleys,
and features on maps appear
changeless. Of course, the
perceived permanence is
illusion. It arises because one
lifetime of experiences is small
beyond imagination, relative to
deep time, and we are not
naturally attuned to looking to
see the tiny subtle variations
that might be the key to
envisioning our reality. This
exercise sends students to
gather some simple data and
challenges them to evaluate
field observations in
discussions with others against
multiple hypotheses. Finally, it
leads them to derive their own
awareness of deep time but
based on what they see, not on
what they are told.
The pattern in C (seasonal temperatures in Minnesota) depicts a cyclic pattern that
occurs at regular repeating intervals, an example of Gould’s “…Time’s Cycle.” It
achieves perfect symmetry and regularity in the—the graph of the sine function in
mathematics. Cyclic patterns describe significant natural phenomena and have
character of predictability.
Pattern (D) appears random, but this graph, a rainfall record from Minnesota, is
fractal! In words, a fractal pattern in time manifests as many common events, a
few intervals when events are absent or abnormally small, infrequent large events,
and very rare catastrophic events that would never be anticipated by direct
observation of the usual events (unless one understands already that the pattern is
part of a fractal system). Fractal patterns in time appear “random” but their fractal
character manifest when clearly linear relationships appear from plotting
recurrence interval of events of a given magnitude versus the size of the
magnitude of the event (see left). Hurst (1951) deduced such patterns when he
studied the longest temporal data record for any natural phenomena —the record
of floods on the Nile River. The amazing inherent order described by Hurst led to
the discovery by Benoit Mandelbrot of fractals as a fundamental descriptor for
patterns of natural events. The order present in such a line allows estimate of the
size of larger events, such as a 100-year flood, even though no witness has yet
recorded the event. While, fractal patterns in time can describe magnitudes and
frequency they don’t have the quality of predictability that allows one to say when
a specific event will occur.
www.POSTERPRESENTATIONS.com
Once upon a time, Mother Earth decided to have a housewarming party. She returned from the store at midnight with all the goodies required and
began to mix the dough and prepare refreshments. By 1:02 in the morning, all the dough had been made into cookies. However, the oven overheated
and left the whole house rather smoky and with a disagreeable odor. Even the swimming pool smelled bad. The bacteria and cyanobacteria (those
nicknamed blue-green algae) were early risers and were among the first guests to arrive at about 5:00 A.M. They were very helpful creatures and
worked all through the day on ventilation of the pool and later on the household air. By about 6:30 P.M. in the evening, they had the house freshsmelling, in time for when the first animals began to arrive. By 9:00 P.M., the party was really hopping! All kinds of strange and wonderful creatures
greeted the fish and shell fish at the door, and many guests came and went. The Coral family arrived at 9:15. Shortly before 10:00 P.M., the amphibians
joined the party at the edge of the pool, and they brought with them potted plants and even trees as housewarming gifts. The guests grew numerous,
and there were so many plants that soon the area around the pool was converted into a garden. Many guests of the party had moved from pool to the
garden by just after ten o'clock. However, all those plants had attracted a number of flying insects, so that by 10:15 P.M. it became very difficult to
carry on conversation there. The reptiles arrived at about 10:20 P.M., but they enjoyed the garden—they were neither bothered much by insects nor
were they enthusiastic conversationalists.
Patterns of exponential decay or growth fit only a limited number of natural phenomena over deep time. Decay of
radioactive parent and growth of daughter products fit this. Exponential patterns largely describe how humans
operate. Consider our economic system, savings accounts, retirements, etc. that depend upon exponential growth.
Our population growth that strains global resources is an unprecedented event in Earth history.
The awareness of patterns can be developed by getting
students to match various processes with the patterns
under which they operate. Consider the following:
rainfall,tides, flooding, landslides, sunspots, diurnal
cycles, tsunamis, earthquakes, change in speed of
Earth’s rotation, mass of Earth. What patterns describe
each through deep time. In-class drills with discussion
that use “Visible Quiz” in conjunction with PowerPoint
are an easy way to produce an interactive PowerPoint
presentation and develop discussion.
Cutting of the Grand Canyon
The pattern that best describes the event above is
A - Constant
B - Rhythmic (cyclic)
C - Fractal
D - Exponential
Then a large group of boisterous dinosaurs came in the door at about a quarter-to-eleven. They swaggered, stomped and ran about, and frightened
many of the guests, including the birds and small mammals who had arrived just a few minutes before 11:00. Most of the guests kept their distance
from the dinosaurs, but the dinosaurs had such a wild time that they were soon exhausted. The fireworks caused the larger ones and most of the other
guests to leave the party abruptly at 11:38 P.M— never to return. The garden had gotten muddy from all the stompings and carryings on, so when some
newly arrived large mammals and a troupe of new guests saw the state of things, they decided the garden would look better with some sod. They
worked quickly and in less than ten minutes had the garden quite beautiful with lush grass. Ma Earth's house was back in very good shape by a quarter
to midnight.
Eight minutes before midnight, the doorbell rang and Ma greeted some hominids at the door. Unlike the reptiles, the hominids were very vocal and all
enjoyed polite chit-chat for a few minutes until 30 seconds before midnight when the first humans finally arrived.
The early arrivals were polite and fit in well at the party, but problems started when the later human creatures presumed that the party was just for
them. They were surprised to learn that so many guests had come and gone already. "Are we really so very late?" they asked incredulously. They were
not too well mannered to the other creatures either. They began to tear up the trees and grasses and quarrel with one another. They even smoked and
insulted the algae and soon the house quickly began to smell stale. Ma Earth warned them that unless they learned better manners, they would have to
leave.
All fell silent at the stroke of midnight, as all the guests watched to see what the humans would do.
Volume of ocean water past
500 million years
The pattern that best describes the event above is
A - Constant
B - Rhythmic (cyclic)
C - Fractal
D - Exponential
General Education Goal Outcome: It is important to understand where ideas
and concepts came from and how we obtained them. Pick a concept from this
core science course, and explain its historical development.
Goal met by learning development of the concept of “Deep
Time.” Teaching Method : A Mystery Séance
A Dozen Spirits: A Séance on Change through Ti me!
Structured Group Work
A fifteen minute lecture on varveforming processes precedes the
group work.
Next, students in groups of four
have the diagram to left from Elk
Lake, Minnesota. Groups draw
cards that have the following roles:
Age Group
Duration Group
Frequency Group
Ordering of Events Group
Pattern Group
Rate Group
Our perception of patterns in time often dictates how we interpret phenomena.
Perhaps no other aspect of time suffers more from misperceptions than that of
patterns. The horizontal line (A) shows time’s passage without change. Laymen
who evaluate their observations over years spent in their geological environment
often report perceptions of comforting stability and permanence described by this
line.
The inclined line with positive slope (B) shows change at a gradual, constant rate.
The graph of gradual change expresses the perception of change taught by Charles
Lyell as the manner through which natural processes act. Statements such as the
Earth is governed by processes that "never acted with different degrees of energy
from that which they now exert" (Lyell, 1829) and "... All theories are rejected
which involve the assumption of violent catastrophes and revolutions of the whole
earth and its inhabitants...theories which are restrained by no reference to existing
analogies..." (Lyell, 1842) reveal Lyell’s devotion to gradualism. Despite the fact
that few “existing analogies” in geology really operate in ways that fit Lyell’s
gradualism, geologists interpreted phenomena in accord with his views for over a
century. Specialized departments and “majors” were not prevalent in Lyell’s time,
so all who attended university were likely to have read his Principles of Geology.
The consequential reach of his dogmatism even into modern thinking in many
areas outside science is rarely appreciated.
TEMPLATE AND PRINTING BY:
Highlights of Ma Earth's Housewarming Party
©Edward Nuhfer
Groups spend ten minutes to focus
on that quality and then report out
in order to build an interpretation
of the Elk Lake profile and its
meaning.
PICK A ROLE - WHAT DO YOU
SEE?
Take-home Assignment.
Pick a geological process and explain its temporal
behavior. Consider age, pattern, rate, frequency,
duration and range of magnitudes. (Product was a table
produced by the entire class.)
Topics Chosen by Students
avalanche (snow)
coal mine subsidence
coastal erosion
condensation
coral growth
creep
deforestation
dissolution of calcite
drought
dune movement
Earth's rotation
El Niño
evaporation (Corpus Christi,
TX, USA)
Evaporite accumulation Castile Anhydrite
exfoliation
fault mov ement (San Andreas)
forest fires
glacial mov ement
glacial abla tion
hillside slide
hurricanes
magma crystallization
deltaic sedimententation
oceanic (abyssal)
sedimentation
photosynthesis --O2
production (corn leaves used
as example)
plant growth cycles
plate tectonics
plate tectonics (folding )
rainfall precipitation
Rocky Mountain building
sea floor spreading
sea level change
sedimentation in a ma n-made
reservoir
sedimentation in a lake
solifluction
sorting
stalactite growth
stromatolite growth
sunspots
tectonic upli fting
tida l cycles
tornado
tree ring growth
volcanism
winds at Earth's surface
Jigsaw Activity
Create a rate table as a class project.
Each student picks a unique topic that
cannot be duplicated. Results are
emailed to instructor who distributes
the class product as a reference.
The following lists people wh ose contribut ions are e ssential to our understanding of geologic time.
Suppos e we held a séance and the spirit of each could speak to our class. Each person could tell
something about him/her self th at would help us t o capt ure the history of the development of ou r
thinking. However, these spirits do not have the good ta ste to app ear in order in wh ich they lived!
It 's up t o us to sort out what they tell into a correct order—to or der the events in time. The tabl e is
in the correct or der, bu t the order in wh ich the sprits actually app ear is not the order of the table,
bu t rather is in the order of letters with their wo rds below the table. Your first task is to us e your
own wits to match the letter of the quote with the individual who would most likely provide such
information. Wr ite your first tries in column A. Tomorrow, we'll work briefly in groups of four to
see if you can improve compilation of matching stateme nts (letters) with persons. After this, we'll
work together to complete the table as a group i n column C.
Person
A-my
first try
B- Our
Group t ry
C-correct
match
1.
2.
3.
4.
5.
6.
7.
Nicolaus Steno (Neils Stensen) (1669)
William Smith (1769-1839),
Baron Georges Cuvier (1769-1832)
James Hutton (work of 1795)
Charles Lyell (1797 - 1875),
Charles Darwin (work of 1859),
William Thomson (Lord Kelvin - work in
1897),
8. John Joly (work of 1908),
9. Thomas Chamberlin (work of 1899 - 1909),
10. Madame Curie (1867 - 1934),
11. Bertram B. Boltwood (work 1905 - 1909) ,
12. Stephen Jay Gould (work 1972 –2000)
A. “I was an engineer--a canal builder. I w as the first to know that fossils found within a bed of rock can
be traced. Even after the layer has disappeared locally, it may be rediscovered at some distant outcrop
and the fossils within it matched to the original site. My work was even recently honored in a bestseller
book in 2001 -- The Map That Changed the World…”
B. The earth is governed by processes that "never acted with different degrees of energy from that which
they now exert." "All theories are rejected which involve the assump tion of violence and catastrophes
and revolutions of the whole earth and its inhabitants...theories which are restrained by no reference to
existing analogies..." I wrote the first geology text, and my thinking affected the way every geologist
saw Earth events up until about the 1970s. I was also a la wyer, and so I tended to argue well and be
quite nasty. I used my influence to detract from those who disagreed with my views.
C. I was influenced greatly by the lawyer. I upset many folks with what I discovered. In fact, I probably
upset more people than anyone on your list! Who could have guessed that studying a bunch of *!#!!
finches would have caused such a ruckus?! I b elieved that among fossils were animals that could be
our ancestors and that the rock record would reveal this. I was concerned however, that we did not find
much in the gradual changes of one form to another in fossils. I at tributed this to the fact that we just
had not studied enough rock to yet have a detailed record that would reveal all the missing links.
D. I was a famo us physicist. My laws that I d iscovered about the rate of cooling of objects and the
equations that describe these are still in use in your time. I cal culated the age of the Earth to be about
100 million years old based on my calculations of radiative cooling. I figured that if Ear th were red
hot, just like a heated cannonball when it was formed, it would cool in accord with the same equations
that could describe the iron cannonball. That always came out to be about 100 million years old.
PHEW! The geologists hated that! Whenever they objected to my age estimate, I told them to go
home and learn some arithmetic, and when they could make a mathematical argument as good as mine,
then we’d talk. They REALLY hated that!
E. I was a great fan of the dual recipient of the Nobel Prize. I studied the work of others and found
that lead was always present in uranium and thorium ores. I d educed that if lead was the final product
of the radioactive decay of uranium and thorium, I c ould measure the rate at which uranium breaks
down (its half-life), I might use the proportion of lead in uranium ores as a k ind of clock. This of
course was based on quite rigorous mathema tics, and there was no question this time about “status.”
We had numbers with real snob appeal! The first ore I d ated put Earth's age at 2.2 billion years. This
was a dr amatic increase in the estimate of Earth's age --- so dramatic that it shocked physicists and
geologists alike. Probably the geologist from the Midwest would have been taken aback, even as mu ch
as he would have loved to live to see the day!
F. I was both a scientist and a roma ntic! I liked to dance and ice skate and had my heart broken
when my first love would not marry me because of my lesser economi c class. I w ent on to become
educated and eventually found both love and success. The word you now use: “radioactivity?” It came
from me. I discovered radium and was the first person ever to be awarded two Nobel prize s--one in
physics and one in chemistry! I shared one award jointly with my dear husband and colleague, Pierre. I
also discovered the nature of radioactive decay. While I really wasn’t concerned mu ch with the
arguments of geologists, my discovery surely knocked the props out from under that age of Earth
derived from the heated cannonball. Pierre and I s howed that radioactive decay released heat. If
radioactive material heats the Earth within, it surely would do nasty things to any mo dels that assume d
a regular rate of cooling!
G. I passed recently from this life in 2002. Most of you have probably read at least one of my books
or essays or had seen me on television. I loved teaching; I delighted in wr iting books for non-scientists,
and I had a particular gift for it. I worked with a colleague at the Museum of Natural History on that
issue of change through time, and together we concluded that the influential lawyer should have paid
more attention to what he was seeing and less on being argumentative. We could not agree with the
lawyer’s view that change through time was gradual. In fact, if one really looks at how things change,
nothing much works that way in geology. Instead, we saw a rather jagged pattern of change punctuated
by stops and then great changes. It affects organisms, and it affects a large numb er of natural changes.
Many things occur as punctuated events. The lawyer in fact did do exactly what he claimed—he
influenced what geologists saw for over a c entury! The inability to perceive the obvious simp ly
because one has been told to see something else is a profound lesson to all f uture scientists.
H. I did my work around the time of the physicist. I calculated the age of the earth to be about 80 - 90
million years old based on ocean salinity. I assumed the first oceans came from rainwater and were
fresh, and that streams ran in with mobile ions like Na+ and so forth, so all I had to do was to calculate
how long it would take the oceans to come to their present salinity based on contributions of dissolved
substances from all the world’s rivers. I w as quite pleased to see my age turn out about the same as the
physicist’s. It gave me confidence. In fact, so much confidence that I never could accept the value of
the later me thods that disproved my age estimates.
I. I was a contemp orary of the canal builder and was first to consider: “Why are some fossils
restricted only to certain layers, and most of them lack any living counterpart?” I proposed that there
have been catastrophic extinctions. "Why has not anyone seen that fossils alone gave birth to a theory
about the forma tion of the earth, that without them, no one would have ever dreamed that there were
successive epochs in the formation of the globe." I was darned unpopular with some others because of
this statement.
Solve the Séance mystery! Try your hand at the exercise on the three
page handout. The answer key follows.
We can understand the relative ages of rock. The oldest layers were lain down first,
and are thus at the bottom of a sequence. 1 - J Nicolaus Steno
“I was an engineer--a canal builder. I was the first to know that fossils found within a
bed of rock can be traced. Even after the layer has disappeared locally, it may be
rediscovered at some distant outcrop and the fossils within it matched to the original
site. My work was even recently honored in a bestseller book in 2001, The Map That
Changed the World…” 2 - A William Smith
I was a contemporary of the canal builder and was first to consider: “Why are
some fossils restricted only to certain layers, and most of them lack any living
counterpart?” I proposed that there have been catastrophic extinctions. 3 - I
Baron Georges Cuvier.
I deduced relative dating principles of cross-cutting relationships. My name is most
often associated with the phrase “The present is the key to the past.” By this, I
meant that we could understand and explain about all we could find in the rock
record if we understood what was happening on the Earth’s surface today. For that
I’m sometimes called “The Father of Modern Geology.” 4 - K James Hutton
The earth is governed by processes that "never acted with different degrees of energy
from that which they now exert." "All theories are rejected which involve the
assumption of violence and catastrophes and revolutions of the whole earth and its
inhabitants...theories which are restrained by no reference to existing analogies..." I
wrote the first geology text… 5 - B Charles Lyell.
I was influenced greatly by the lawyer. I upset many folks with what I
discovered. In fact, I probably upset more people than anyone on your list! Who
could have guessed that studying a bunch of *!#!! finches would have caused
such a ruckus?! I believed that among fossils were animals that could be our
ancestors and that the rock record would reveal this… 6 - C Charles Darwin.
I was a famous physicist. My laws that I discovered about the rate of cooling of
objects and the equations that describe these are still in use in your time. I
calculated the age of the Earth to be about 100 million years old based on my
calculations of radiative cooling. I figured that if Earth were red hot, just like a
heated cannonball when it was formed, it would cool in accord with the same
equations that could describe the iron cannonball. That always came out to be
about 100 million years old. PHEW! The geologists hated that! 7 - D William
Thomson (Lord Kelvin)
I did my work around the time of the physicist. I calculated the age of the earth to be
about 80 - 90 million years old based on ocean salinity. I assumed the first oceans came
from rainwater and were fresh, and that streams ran in with mobile ions like Na+ and
so forth, so all I had to do was to calculate how long it would take the oceans to come
to their present salinity based on contributions of dissolved substances from all the
world’s rivers. I was quite pleased to see my age turn out about the same as the
physicist’s. 8 - H John Joly.
I was largely self-taught and grew up in the Midwest. I eventually graduated from
a small college there, and I became one of the world’s most influential geologists
and educators. I was devoted to teaching others how to teach themselves. I
deduced a major method of science—the method of “multiple working
hypotheses." I certainly am one person the physicist referred to--I hated his 100
million year old age limit for Earth. 9 - L Thomas Chamberlin
The word you now use: “radioactivity?” It came from me. I discovered radium
and was the first person ever to be awarded two Nobel prizes--one in physics
and one in chemistry! I shared one award jointly with my dear husband and
colleague, Pierre. I also discovered the nature of radioactive decay. While I
really wasn’t concerned much with the arguments of geologists, my discovery
surely knocked the props out from under that age of Earth derived from the
heated cannonball. 10 - F Marie Curie.
I was a great fan of the dual recipient of the Nobel Prize. I deduced that if lead was
the final product of the radioactive decay of uranium and thorium, I could measure
the rate at which uranium breaks down (its half-life), I might use the proportion of
lead in uranium ores as a kind of clock. The first ore I dated put Earth's age at 2.2
billion years. This was a dramatic increase in the estimate of Earth's age --- so
dramatic that it shocked physicists and geologists alike. 11 - E Bertram Boltwood
I passed from this life in 2002. Most of you have probably read at least one of my
books or essays. I delighted in writing books for non-scientists, and I had a particular
gift for it. I worked with a colleague at the Museum of Natural History on organisms’
change through time, and we saw a rather jagged pattern of change punctuated by
stops and then great changes. A large number of natural changes occur as punctuated
events. 12 - G Stephen Jay Gould