Unit Name: “Blast from the Past”, A
Study of Meteorite Impact Craters based on research from The Ocean Drilling
Program, the Smithsonian National Museum of Natural History, and
Research from the Lamont-Doherty Earth Observatory.
Background: This unitis a student-centered, problem solving approach to earth science that is
based on interaction between research scientists, teachers and students.
Resources came from the scientific research community from the Lamont-Doherty
Earth Observatory (LDEO), the Integrated Ocean Drilling Project (IODP), Hawaii
Institute of Geophysics and Planetology. This curriculum has been developed
through the Earth2Class Project (E2C), which is supported by the National
Science Foundation and links research Scientists with classroom teachers.
Special thanks to Dr. Gerardo Iturrino of LDEO Borehole Research Group and IODP,
Dr. Dallas Abbott of LDEO, and Dr. Pearl Solomon of St. Thomas Aquinas College
for their patience and contributions to the K-12 education.
Unit Time Frame: 5 – 45 minute classes
Content Standards:
Standard 1 – Analysis, Inquiry and Design:
Mathematical Analysis
Key Idea 2: Deductive and
inductive reasoning are used to reach mathematical conclusions.
Key Idea 3: Critical
thinking skills are used in the solution of mathematical problems.
Analysis, Inquiry and Design: Scientific
Inquiry
Key Idea 1: The central
purpose of scientific inquiry is to develop explanations of natural phenomena in
a continuing, creative process.
Key Idea 2: Beyond the
use of reasoning and consensus, scientific inquiry involves the testing of
proposed explanations involving the use of conventional techniques and
procedures and usually requiring considerable ingenuity.
Key Idea 3: The
observations made while testing proposed explanations, when analyzed using
conventional and invented methods, provide new insights into phenomena.
Standard 4 -
Key Idea 1: The Earth and
celestial phenomena can be described by principles of relative motion and
perspective.
Key Idea 4: Energy exists
in many forms, and when these forms change energy is conserved.
Performance Standards:
General Skills
1. Follow safety procedures in the classroom
and laboratory.
2. Safely and accurately use a metric ruler
and balance.
3. Use appropriate units for measured or
calculated values.
4. Recognize and analyze patterns and trends.
5. Identify cause-and-effect relationships
Physical Setting Skills
1. Given the latitude and
longitude of a location, indicate its position on a map and determine the
latitude and longitude of a given location on a map.
Enactment Standards
All of the basic activities in this unit can be
conducted within the classroom using the following materials:
·Large aluminum pan,
·Flour
·Colored sands
·Colored tile grout or mortar mix
·Several minerals or rocks approximately 2-4 cm, such as, galena,
pyrite (marbles may be substituted)
·Metric ruler or tape
·Triple beam balance
·Newspaper or plastic drop sheet
·Safety goggles
·Optional camera and film, flashlight or other light source. A
video camera set of slow motion is also a helpful means of analyzing simulated
crater impacts
·Road maps of the students’ country, state of local area
·World map
·Piece of 8.5 x 11.0 in plastic sheet
·Compass
·Transparency markers
·Scissors
·30 cm ruler
·World atlas
·Student worksheets and graph paper
·Word Chart
·Index Cards
·Textbook
Activities
Day 1 –
Introduce and engage students by showing them the “Blast from the Past” poster
and discussing the Mass Extinctions of the Cretaceous. Develop vocabulary using
index cards and word Chart. Divide students into labGroups (Meteorite
Evaluation Teams) and give them a schedule of the upcoming activities for the
week. Establish lab safety procedures and expectations for work product.
Day 2 -
“Let’s Make an Impact Crater”, Activity 1 from “Blast from the Past” (see
attachment). Modify as needed using resources such as
www.meteorcrater.com
and
http://www.spacegrant.hawaii.edu/class_acts/CrateringDoc.html.
For further definitions, and illustrations, also have the students consider www.solarviews.com/eng/tercrate.htm, which has definitions of
potential projectiles and different forms of craters. It has a reference to a
term glossary on the web. The website www.lpi.usra.edu/publications/slidesets/craters/has a large
collection of images, and a mores specific glossary in relation to craters. The
website www.lpl.arizona.edu/SIC/impact_cratering/intro/
has interesting discussions regarding the environmental impact of impact
craters, including the effect on life and evolution of species of impact
craters. Would bring relevance to the importance of studying impact craters and
the study of why we track Solar System debris. After the students have had
sufficient time to explore the different websites, you may wish to distribute
assignments as to which sites each group is to visit) have each group display
and discuss their results.
Optional: Student group
whiteboards and markers may help the students in their presentations. [Note:
WebQuest linking the above listed websites is in progress and will posted to
this activity in the future.]
Day 3 - Review Activity 1 and
Reinforce any concepts/skills in which the students need help. Use the Word
Chart to have students develop and define vocabulary in their own words.
Day 4 – “Just How Big Was the Blast
that Caused the Dinosaurs to Become Extinct”, Activity 2 from “Blast from the
Past” (see attachment for reference, note images did not copy). Modify as
needed and incorporate internet resources if possible. Use Word Chart to assist
students in vocabulary.
Day 5 -
Assess students understanding and skills with a quiz. Follow-up with additional
lessons/extra help if necessary.
Optional Extensional Activities
Have students prepare poster
presentations about meteorite impact craters.
Have students research impact craters on Mars
and or other celestial bodies.
Have students develop and independent science
project based on current research.
Have students identify crater features using
the activity listed in the website:
Hawai'i Space Grant College, Hawai'i Institute
of Geophysics and Planetology, University of Hawai'i, 1996
Impact Craters
Teacher Page
Purpose
To determine the factors affecting the appearance of
impact craters and ejecta.
Background
The circular features so obvious on the Moon's surface are
impact craters formed when impactors smashed into the surface. The
explosion and excavation of materials at the impacted site created piles of rock
(called ejecta) around the circular hole as well as bright streaks of
target material (called rays) thrown for great distances.
Two basic methods that form craters in nature are:
1) impact of a projectile on the surface and 2)
collapse of the top of a volcano creating a crater termed caldera.
By studying all types of craters on Earth and by creating
impact craters in experimental laboratories, geologists concluded that the
Moon's craters are impact in origin.
The factors affecting the appearance of impact craters and
ejecta are the size and velocity of the impactor, and the geology of the target
surface.
By recording the number, size, and extent of erosion of
craters, lunar geologists can determine the ages of different surface
units on the Moon and can piece together the geologic history. This technique
works because older surfaces are exposed to impacting meteorites for a
longer period of time than are younger surfaces.
Impact craters are not unique to the Moon. They are found
on all the terrestrial planets and on many moons of the outer planets.
On Earth, impact craters are not as easily recognized
because of weathering and erosion. Famous impact craters on Earth are Meteor
Crater in Arizona, U.S.A.; Manicouagan in Quebec, Canada; Sudbury in Ontario,
Canada; Ries Crater in Germany, and Chicxulub on the Yucatan coast in Mexico.
Chicxulub is considered by most scientists as the source crater of the
catastrophe that led to the extinction of the dinosaurs at the end of the
Cretaceous period. An interesting fact about the Chicxulub crater is that you
cannot see it. Its circular structure is nearly a kilometer below the surface
and was originally identified from magnetic and gravity data.
This activity was adapted from a cratering activity
developed by Karen Nishimoto and Robin Otagaki, Punahou School.
Lunar Impact Crater
Typical characteristics of a lunar impact crater are
labeled on this photograph of Aristarchus, 42 im in diameter, located West of
Mare Imbrium.
Common
definitions:
floor
bowl shaped or flat, characteristically below surrounding ground level unless
filled in with lava.
ejecta
blandet of mateial surrounding the crater that was exzcavated during the impact
event. Ejecta becomes thinner away from the crater.
raised rim
rock thrown out of the crater and deposited as a ring-shaped pile of debris at
the crater's edge during the explosion and excavation of an impact event.
walls
characteristically steep and may have giant stairs called terraces.
rays
bright streaks starting from a crater and extending away for great distances.
See Copernicus crater for another example.
central uplifts
mountains formed becuase of the huge increase and rapid decrease in pressure
during the impact event. They occur only in the center of craters that are
larger than 40 km diameter. See Tycho crater for another example.
"Models of Impact Craters"
Activity
In this activity, marbles or other spheres such as steel
shot, ball bearings, or golf balls are used as impactors that students drop from
a series of heights onto a prepared "lunar surface." Using impactors of
different mass dropped from the same height will allow students to study the
relationship of mass of the impactor to crater size. Dropping impactors from
different heights will allow students to study the relationship of velocity of
the impactor to crater size.
Preparation
Review and prepare materials listed on the student sheet.
The following materials work well as a base for the "lunar
surface." Dust with a topping of dry tempera paint, powdered drink mixes glitter
or other dry material in a contrasting color. Use a sieve, screen , or flour
sifter. Choose a color that contrasts with the base materials for most striking
results.
All-purpose flour
Reusable in this activity and keeps well in a covered container.
Baking soda
It can be recycled for use in the lava layering activity or for many other
science activities. Reusable in this activity, even if colored, by adding a
clean layer of new white baking soda on top. Keeps indefinitely in a covered
container. Baking soda mixed (1:1) with table salt also works.
Corn meal
Reusable in this activity but probably not recyclable. Keeps only in freezer in
airtight container.
Sand and corn starch mixture
Mixed (1:1), sand must be very dry. Keeps only in freezer in airtight container.
Pans should be plastic, aluminum, or cardboard. Do not use glass. They should be
at least 7.5 cm deep. Basic 10"x12" aluminum pans or plastic tubs work fine, but
the larger the better to avoid misses. Also, a larger pan may allow students to
drop more marbles before having to resurface and smooth the target materials.
A reproducible student "Data Chart" is included; students
will need a separate chart for each impactor used in the activity.
In Class
1. Begin by looking at
craters in photographs of the Moon and asking students their ideas
of how craters formed.
2. During this activity, the
flour, baking soda, or dry paint may fall onto the floor and the
baking soda may even be disbursed into the air. Spread newspapers under the
pan(s) to
catch spills or consider doing the activity outside. Under supervision,
students have
successfully dropped marbles from second-story balconies. Resurface the pan
before a
high drop.
3. Have the students agree beforehand on the method they will use to "smooth"
and resurface the material in the pan between impacts. The material need not be
packed down. Shaking or tilting the pan back and forth produces a smooth
surface. Then be sure to reapply a fresh dusting of dry tempera paint or other
material. Remind students that better experimental control is achieved with
consistent handling of the materials. For instance, cratering results may vary
if the material is packed down for some trials and not for others.
4. Allow some practice time for dropping marbles and resurfacing the materials
in th
pan before actually recording data.
5. Because of the low
velocity of the marbles compared with the velocity of real
impactors, the experimental impact craters may not have raised rims. Central
uplifts
and terraced walls will be absent.
6. The higher the drop
height, the greater the velocity of the marble, so a larger crater
will be made and the ejecta will spread out farther.
7. If the impactor were
dropped from 6 meters, then the crater would be larger. The
students need to extrapolate the graph out far enough to read the predicted
crater
diameter.
Wrap-Up
Have the class compare and contrast their hypotheses on
what things affect the appearance of craters and ejecta.
Extensions
1. As a grand finale for your students, demonstrate a more forceful impact using
a slingshot.
2. What would happen if you change the angle of impact? How could this be
tested? Try it! Do the results support your hypothesis?
If the angle of impact is changed, then the rays will be concentrated and
longer in the direction of impact. A more horizontal impact angle produces a
more skewed crater shape.
3. To focus attention on the rays produced during an impact, place a paper
bulls-eye target with a central hole on top of a large, flour-filled pan.
Students drop a marble through the hole to measure ray lengths and orientations.
4. Use plaster of Paris or wet sand instead of dry materials.
5. Videotape the activity.
6. Some people think the
extinction of the dinosaurs was caused by massive global climate changes because
of a meteorite
impact on Earth. Summarize the exciting work that has been
done at Chicxulub on the Yucatan coast of Mexico.
7. Some people think Earth
was hit by an object the size of Mars that caused a large part of Earth to
"splash" into space,
forming the Moon. Do you agree or disagree? Explain your
answer.
8. Physics students could
calculate the velocities of the impactors from various heights. (Answers from
heights of 30 cm,
60 cm, 90 cm, and 2 m should, of course, agree with the
velocity values shown on the "Impact Craters - Data Chart".
To determine the factors affecting the
appearance of impact craters and ejecta.
Key Words
impact
impactor
ejecta
Materials
1 pan
"lunar" surface material
tempera paint, dry
sieve or sifter
balance
3 impactors (marbles or other spheres)
meter stick
ruler, plastic with middle depression
protractor
"Data Chart" for each impactor
graph paper
Making an hypothesis
1.
After looking at photographs of the Moon, how do you think
the craters were formed?
2.
What do you think are factors that affect the appearance of
craters and ejecta?
Preparing a "lunar" test surface
1.
Fill a pan with surface material to a depth of
about 2.5 cm. Smooth the surface, then tap the pan to make the materials
settle evenly.
2.
Sprinkle a fine layer of dry tempera paint evenly and
completely over the surface. Use a sieve or sifter for more
uniform layering.
3.
What does this "lunar" surface look like before testing?
Cratering Process
1. Use the balance to
measure the mass of each impactor. Record the mass on the "Data Chart"
for this impactor.
2. Drop impactor #1 from a
height of 30 cm onto the prepared surface.
3. Measure the
diameter and depth of the resulting crater.
4. Note the presence of
ejecta (rays). Count the rays, measure, and determine the average length of all
the rays.
5. Record measurements and
any other observations you have about the appearance of the crater on the Data
Chart. Make three trials and compute the average values.
6. Repeat steps 2 through 5
for impactor #1, increasing the drop heights to 60 cm, 90 cm, and 2 meters.
Complete the Data
Chart for this impactor. Note that the higher the drop
height, the faster the impactor hits the surface.
7. Now repeat steps 1
through 6 for two more impactors. Use a separateData Chart for each
impactor.
8. Graph your results. Graph
#1 is Average crater diameter vs. impactor height or velocity. Graph #2 is
Average ejecta (ray)
length vs. impactor height or velocity. Note: on the
graphs, use different symbols (e.g., dot, triangle, plus, etc.) for different
impactors.
Results
1. Is your hypothesis about
what affects the appearance and size of craters supported by test data? Explain
why or why not.
2.What do the data reveal
about the relationship between crater size and velocity of impactor.
3. What do the data reveal
about the relationship between ejecta (ray) length and velocity of impactor.
4. If the impactor were
dropped from 6 meters, would the crater be larger or smaller? How much larger or
smaller?
Explain your answer. (Note: the velocity of the impactor
would be 1,084 centimeters per second.)
5. Based on the experimental
data, describe the appearance of an impact crater.
6. The size of a crater made
during an impact depends not only on the mass and velocity of the impactor, but
also on the
amount of kinetic energy possessed by the impacting object.
Kinetic energy, energy in mostion, is described as:
KE = ½ mv2
where, m
= mass and v
= velocity.
During
impact, the kinetic energy of an asteroid is transferred to the target surface,
breaking up rock and moving the particles around.
7. How does the kinetic
energy of an impacting object relate to crater diameter?
8. Looking at the results in
your Data Tables, which is the most important factor controlling the kinetic
energy of a projectile, its diameter, its mass, or its velocity?
9. Does this make sense? How
do your results compare to the kinetic energy equation?
10. Try plotting crater
diameter vs. kinetic energy as Graph #3. The product of mass (in grams) and
velocity (in centimeters per second) squared is a new unit called "erg."
Support |
Links
