Geology

Beach Bum Science: Compression of Wet Sand (from http://sciencebuddies.com/science-fair-

projects/project_ideas/Geo_p023.shtml?fave=no&isb=c2lkOjEsaWE6R2VvLHA6MixyaWQ6MzI5MzU5MQ&from=TSW)

Objective The goal of this project is to investigate what happens to the volume of wet sand under compression. Introduction Have you ever taken a barefoot stroll on the beach? Right next to the water, the sand feels cool under your toes, and it's packed nice and firm so you can get good traction. You can hear the waves, over and over. Sometimes the water runs over your feet. If you look down at the wet sand, you can see that the pressure from your feet has effects over several times the area of your footprint. Marci Rosenberg noticed that, and wondered what was going on. Her investigation turned into a science fair project that brought her all the way to the California State Science Fair where she won a Clever Scientist award from Science Buddies (Rosenberg, 2007). Marci used a simple apparatus made from a balloon and a drinking straw to investigate what happens to wet sand when it is compressed. She filled the balloon with wet sand using a funnel, then she attached a straw inside the neck of the balloon with a rubber band. Next, she taped a ruler to the straw, and filled the straw part-way with water. Her apparatus looked something like the drawing in Figure 1, below. By squeezing on the balloon with a C-clamp, she could apply pressure to the wet sand (like your foot does when you walk on the beach). By measuring the change in water level in the straw, she could observe what happened to the volume of the wet sand in the balloon as the pressure increased.

© Mary Marin

Figure 1. Schematic diagram of Marci's balloon and straw apparatus. The balloon is filled with wet sand. A straw goes inside the neck of the balloon, and is attached tightly with a rubber band. A ruler is taped to the straw, and the straw is filled part-way with water.

What do you think will happen to the water level in the straw when the balloon is squeezed? Your intuition probably tells you that the water level will rise. You may have some experience with water balloons, and this is probably what you would expect to happen if the balloon was filled only with water. In general, fluids have a property called "incompressibility." This means that if you squeeze a fluid, you generally cannot reduce the volume. For example, if you squeeze a water balloon, the balloon doesn't get smaller, the water just moves someplace else. If you apply enough pressure, the water will stretch the rubber side of the balloon, perhaps even breaking it. The principle of incompressibility of fluids has applications in everyday life (in addition to water balloons, that is!). Hydraulic pistons are used in the brake systems and shock absorbers in cars, for lifting barber chairs, and for moving the heavy arms of construction equipment (see Figure 2). See the references in the Bibliography section to learn the details of how hydraulic pistons work (Brain, 2007; Rosignol, 2007).

Figure 2. Hydraulic pistons at work. The arm and bucket of this excavator can be maneuvered with hydraulic pistons. The diesel engine powers a hydraulic pump which is connected to each of the cylinders via control valves. (© Parrus)

Unlike liquids, gases can be squeezed into smaller spaces (if you have a container that will withstand the increased pressure). As a result, air bubbles cause problems in a hydraulic system. When there is an air bubble in the hydraulic fluid in a cylinder, instead of moving the piston the air bubble is compressed first, and only then does the piston start to move. The Experimental Procedure section below will show you how to use the balloon and straw apparatus to find out if wet sand behaves like an incompressible fluid. Find out if your intuition is correct or not! Terms, Concepts and Questions to Start Background Research To do this project, you should do research that enables you to understand the following terms and concepts:

• Volume • Incompressibility of fluids • Hydraulic pistons • Structure of sand

Questions

• What will happen to the water level in the straw when the balloon is filled with tap water and then squeezed?

• What will happen to the water level in the straw when the balloon is filled with wet sand and then squeezed?

• What happens to a hydraulic system if there is an air bubble trapped inside? Bibliography

• For information on how hydraulic systems work, see these webpages: o Brain, M., 2007. "How Hydraulic Machines Work," Howstuffworks, Inc.

[accessed June 18, 2007] http://science.howstuffworks.com/hydraulic.htm. o Rosignol, R.C., 2007. "How Does a Hydraulic Jack Work?" PhysLink.com

[accessed June 18, 2007] http://www.physlink.com/Education/askExperts/ae526.cfm.

• Astronauts bringing sand into space? Here is a cool article from NASA on the properties of sand under pressure: Barry, P.L., 2002. "The Physics of Sandcastles," National Aeronautics and Space Administration [accessed June 18, 2007] http://science.nasa.gov/headlines/y2002/11jul_mgm.htm.

• Here's some good background information on the structure of sand: Armstrong, W.P., . "Sand Grains: Chips Off the Old Rock," Wayne's Word, An Online Textbook of Natural History [accessed June 18, 2007] http://waynesword.palomar.edu/ww0704b.htm.

• This project is based on the following 2007 California State Science fair project, a winner of the Science Buddies Clever Scientist Award: Rosenberg, M.F., 2007. "The Effect of Compression on Granular Media," [accessed June 18, 2007] http://www.usc.edu/CSSF/History/2007/Projects/J0723.pdf.

Materials and Equipment To do this experiment you will need the following materials and equipment:

• Package of round balloons, all the same size • Straw • Rubber band • Metric ruler • Tape • Funnel • Cardboard box (e.g., corrugated cardboard shoe box) • Utility knife • C-clamp • Materials for filling balloons, for example:

o Wet sand (try different grain sizes, different amounts of water added to the sand)

o Plain tap water o Salt water o Salt slurry (saturated salt solution with additional, undissolved salt) o Fine aquarium gravel and water o Clay (very fine grains) and water o Different types of soil and water

Experimental Procedure

1. Do your background research so that you are familiar with the terms, concepts, and questions, above.

2. In addition to the balloon and straw described in the Introduction, you'll need a C-clamp to squeeze the balloon. To support the C-clamp at the correct height, prepare a sturdy cardboard box (like a corrugated cardboard shoe box) as shown in the diagram below:

Shoebox support for C-clamp. The balloon is supported from above by the straw, and hangs inside the hole cut in the box. Adjust the height so that the jaws of the clamp are in the middle of the balloon.

a. Cut a hole in the box at one end, with a diameter just slightly larger than

the diameter of your balloons. b. The C-clamp will rest on top of the box. c. You'll attach the straw (e.g., tape it to a kitchen cabinet) so that the

balloon hangs down into the hole. d. The middle of the balloon should be even with the jaws of the C-clamp.

3. Place the box on the kitchen counter, beneath the cabinet that you will use for supporting the balloon and straw apparatus.

4. Put the C-clamp on top of the box, surrounding the hole. With the C-clamp in place, you'll be able to see the correct height for hanging the balloon.

5. Use the funnel to fill the balloon with the substance to be tested. Be consistent: always add the same amount (by volume).

6. Insert a straw far enough into the neck of the balloon so that the end of the straw is in the wet sand. Attach the straw tightly in place with a rubber band around the neck of the balloon. The balloon will be hanging from the straw, so make sure it is on tight!

7. Use (removeable!) tape to attach the straw to a kitchen cabinet. a. Get permission from Mom first! If you mar the cabinets right after a

kitchen remodel she's not going to be too happy! b. The balloon will hang down from the straw. c. Height-wise, you want the mid-point of the balloon to be even with the jaws

of the clamp. 8. Add some water to the straw to fill it part-way (no more than half) with water.

9. Using the ruler taped alongside the straw, record the intial height of the water in the straw, in centimeters (cm). This will be your "zero" point.

10. Adjust the C-clamp until it just "grabs" the sides of the balloon. Record the height of the water in the straw in cm.

11. Tighten the C-clamp one full turn. Record the height of the water in the straw in cm.

12. Repeat the previous step—several times, if possible. Stop if the water is about to overflow the straw.

13. Do at least three separate trials (more is better) for each material. 14. Subtract the "zero" level from each measurement. This will give you a measure of

the amount of water that was displaced during each trial. 15. For each substance tested, calculate the average amount of water displaced over

all trials. 16. More advanced students should also calculate the standard deviation. 17. Make a graph of the amount of water displaced (in cm, y-axis) vs. the increase in

pressure (number of turns of the C-clamp, x-axis). 18. Is the shape of the graph similar for all of the substances? 19. Can you explain the results?

Variations

• For a related experiment that might help explain your results, see the Science Buddies project Sand Structure: Measuring Density and Porosity of Sand.

• For a project with a real "twist" on the concept of a sandbox this Science Buddies experiment shows you how you can build a sandbox with transparent sides and a moveable end to see what happens to layers of sand under compression. You can see how layers are deformed and compare what happens with varying grain sizes, varying amounts of water, etc. Sound interesting? See the Science Buddies project Under Pressure: Sand Under Lateral Compression for more information.

Factors that Affect the Transfer of Force through Saturated Soil

(from http://sciencebuddies.com/science-fair-projects/project_ideas/Geo_p002.shtml?fave=no&isb=c2lkOjEsaWE6R2VvLHA6MixyaW

Q6MzI5MzU5MQ&from=TSW) Objective The objective of this project is to determine what effect additives have on the transfer of force through saturated soil. The reason I performed this investigation was to try to establish if the effects of liquefaction can be prevented or lessened by adding elements to the soil. Introduction In locations with high earthquake potential, the susceptibility of the existing soil to liquefaction can pose problems for building. Is it possible to add elements to the soil to help minimize the effects of liquefaction on sandy soils? Terms, Concepts and Questions to Start Background Research In order to properly conduct this experiment, you will need to understand soil liquefaction. What conditions need to be present for soil liquefaction to occur? What causes soil liquefaction? What methods are currently being used to mitigate liquefaction hazards? You should also develop a good understanding of soil types from an engineering perspective, i.e. what makes for a "solid" soil vs. a less stable soil given the potential force of an earthquake. How will your "additives" impact the structure of the soil? Bibliography The Soil Liquefaction Web Site from the University of Washington offers a great introduction to liquefaction: http://www.ce.washington.edu/~liquefaction/html/main.html The US Geological Survey web site also has some general information on earthquakes and liquefaction that is written specifically for students grades 7-12: http://earthquake.usgs.gov/4kids/

In 1998 NASA conducted a study on the Mechanics of Granular Materials. They actually took columns of sand and sent them into space so they could further investigate the behaviors of granular materials without the stresses of gravity. The structure of the experiment is similar to the experiment that is being tested here, and offers some good general information and findings on the structure of granular materials and liquefaction. http://science.nasa.gov/newhome/headlines/msad06jan98_1.htm Materials and Equipment

• Section of PVC pipe • Drill • Sandy soil • Experimental Fillers: bark, dried leaves, polymers, and Styrofoam popcorn • Water • Dowels • Weights • Mosquito netting or cheesecloth • Duct tape • Force-measuring device (such as a spring-scale) • Shake table (optional)

Experimental Procedure

1. Drill four holes in the PVC pipe. The holes should be equally spaced vertically and should be sized to fit the dowels that you will be using in the experiment.

2. Cover the bottom of the pipe with the mosquito netting or cheesecloth, which will allow water to seep in while keeping the soil n the pipe.

3. Fill the pipe with soil. 4. Saturate the soil with water by placing the bottom of the pipe in a container

filled with water and letting the water seep into the pipe from the bottom. You will probably need to leave the pipe in the water overnight to give it time to fully saturate. Make sure you use the same amount of water each time.

5. Once the soil is saturated, seal the bottom of the pipe with duct tape to keep the soil and water from seeping out.

6. Quickly insert the four dowels into the holes. 7. Place weights on the soil at the top of the pipe. 8. Wait at least one hour for the soil to settle. To assist the settling of the soil, tap

the pipe lightly two to three times. 9. Drop the pipe three times on a hard surface from a height of approximately two

inches to simulate an earthquake. Alternatively, if you have access to a shake table, this could also be used to simulate the effects of an earthquake. If using a

shake table, you will need to make sure that the pipe remains vertical while on the shake table.

10. Pull out the dowels using a force-measuring device to determine the level of contact forces in the soil.

11. Repeat steps 3-10 combining the additives (bark, dried leaves, polymers, and Styrofoam popcorn) one at a time to the soil to test the ability of each of the additives to reduce the effects of liquefaction.

How Fast Do Seismic Waves Travel? (from http://sciencebuddies.com/science-fair-

projects/project_ideas/Geo_p016.shtml?fave=no&isb=c2lkOjEsaWE6R2VvLHA6MSxyaWQ6MzI5MzU5MQ&from=TSW)

Objective The goal of this project is to use archived, online seismometer data from the Berkeley Digital Seismic Network to create your own seismograms in order to measure how fast seismic waves from distant earthquakes travel through the Earth's crust. Introduction A seismograph is an instrument that detects and records ground motion. As an analogy, think of trying to draw a straight line on a piece of paper while someone is holding your elbow and jiggling it back and forth. It would be hard to get the line straight, wouldn't it! You can think of a seismograph as a machine that is kind of like your arm, holding the pen. The 'elbow' end of the machine detects the vibrations, causing the pen to move back and forth. Meanwhile, a roll of paper is moving at a constant speed under the pen. When there are no vibrations, the pen draws a straight line on the paper. When the ground shakes, it causes the pen to move back and forth, so instead of straight lines, you get up and down squiggles. The greater the vibrations, the larger the squiggles. In the digital age, seismographs have been replaced by seismometers, which measure and record ground motion digitally. The data from seismometers can be collected automatically and analyzed with computers. When an earthquake occurs, how do scientists know how powerful it is? A network of seismometers constantly monitors movements of the Earth's crust. When an earthquake occurs, waves of motion travel out from the epicenter, through the crust, and are detected by the seismometers. By analyzing the differences in the timing of the waves between multiple staions, scientists can pinpoint the source of the waves: the epicenter of the original quake. In this project you will use online seismometer data from the Berkeley Digital Seismograph Network (BDSN) to measure how fast seismic waves from distant earthquakes travel through the earth's crust.

Terms, Concepts and Questions to Start Background Research To do this project, you should do research that enables you to understand the following terms and concepts:

• earthquake, • tectonic plate, • seismograph, • seismogram, • seismometer, • seismology, • Coordinated Universal Time.

More advanced students will also want to study the physics of waves, and should do research to understand the following terms and concepts:

• frequency, • period, • wavelength, and • wave velocity.

Questions

• Do seismic waves generally travel at the same speed or is there variation in wave speed?

• Do seismic waves from more powerful earthquakes travel faster than waves from weaker quakes?

• Do seismic waves travel faster through oceanic crust or continental crust (or about the same through both)?

Bibliography

• To find earthquake information (date, time, location, magnitude), see this webpage: USGS, 2006. "Historic Worldwide Earthquakes," United States Geological Survey, Department of the Interior [accessed December 21, 2006] http://earthquake.usgs.gov/regional/world/historical.php.

• To create a seismogram, see: UC Regents, 2005. "Make Your Own Seismogram!" Northern California Earthquake Data Center, University of California, Berkeley and USGS [accessed December 21, 2006] http://www.ncedc.org/bdsn/make_seismogram.html.

• To measure the great circle distance between two points on the globe, see: Byers, J.A., 1997. "Surface Distance Between Two Points of Latitude and Longitude," United States Department of Agriculture, Agricultural Research Service [accessed December 21, 2006] http://www.chemical-ecology.net/java/lat-long.htm .

• For getting started on your background research, here are two good references on seismology:

o Wood, M.M. and W. Pennington, 2006. "Seismic Education Site: UPSeis," Department of Geological and Engineering Sciences, Michigan Technical University [accessed December 21, 2006] http://www.geo.mtu.edu/UPSeis/index.html.

o Wikipedia contributors, 2006. "Seismology," Wikipedia, The Free Encyclopedia [accessed December 21, 2006] http://en.wikipedia.org/w/index.php?title=Seismology&oldid=96601497.

Materials and Equipment To do this experiment you will need the following materials and equipment:

• computer with Internet access and a printer. Experimental Procedure Select Historic Earthquakes to Analyze

1. Do your background research so that you are knowledgeable about the terms, concepts, and questions, above.

2. Make a table of historic earthquakes to analyze. You can find a list at Historic Worldwide Earthquakes (USGS, 2006).

3. For each earthquake, you'll need at least the following information: o magnitude, o time (UTC), o epicenter location (latitude, longitude, depth).

4. We'll walk through one example to show you where to find the data you need. a. The screenshot below shows a portion of the list at the Historic Worldwide

Earthquakes webpage. To get more information about a particular earthquake, click on the link. We're going to be looking at data from a magnitude 6.3 temblor with epicenter on Kyushu Island, Japan that occurred on June 11, 2006, at 20:01:29 UTC.

b. Clicking on the link for this quake brings us to a page with the information

shown in the screenshot below

c. Copy the information you need for each earthquake (highlighted in yellow rectangles, above).

d. Notice that there are additional tabs (Summary, Maps, Scientific & Technical, highlighted in green rectangle, above) with additional information about each quake. You'll probably be interested in checking out the Summary and Maps tabs for each quake you study.

5. For a simple analysis of seismic wave speed, choose 10–20 earthquakes from (roughly) the same part of the world. For other ideas on criteria for selecting earthquakes to analyze, see the Variations section. Note that, on the right-hand side of the Historic Worldwide Earthquakes page, you can sort the quake data by Date, Magnitude, Magnitude 6.0 and Greater, Country & Date, Country & Magnitude (see screenshot, below).

Make a Seismogram

1. The webpage for making a seismogram is pretty straightforward. Again, we'll walk through an example to show you how to use it.

a. Select a station. Click on one of the radio buttons to select from the 28 available stations. For more information on the stations, see Table 1, below. For our example seismogram, we used data from station BKS, the Byerly Seismographic Vault, near the UC Berkeley campus.

b. Select the data channel. There are two types of data channels: 'long

period' and 'broadband.' The period of a seismic wave is the time that elapses between successive wave crests. Long period waves, then, are low-

frequency waves. The long period channels are good for viewing seismic activity from distant earthquakes, so you should use these channels for this project. You can choose to look at vertical motion, or horizontal motion (either north-south or east-west).

c. The broadband channels collect information more frequently, and so have

information about higher-frequency waves. Broadband channels are good for viewing seismic activity from local earthquakes. See the Variations section for project ideas that can make use of the broadband data channels.

d. Set the desired time period. The seismogram plot can be a maximum of 24 hours for long period data channels (1 hour for broadband data channels). It's a good idea to view seismic data both before and after the time of the earthquake. An easy way to do this is to set the time period to one entire day. Enter the date and time in the format "yyyy/mm/dd,hh:mm:ss". Separate date and time with a comma, but no spaces. In the screenshot below, we have set the plot to cover the entire day of June 11, 2006.

e. Set the plotting parameters. Often, the default parameters will work just

fine. For higher-magnitude quakes, however, you may need to decrease the Amplitude Scaling parameter by a factor of 10 or 20 (or more) so that the active traces do not overwhelm the entire plot. You can also increase the spacing between the traces (third parameter), but this will increase the vertical size of the plots, making them harder to view and print.

f. Make the seismogram! Click on the "Create Plot" button near the bottom of the page. That's it!

2. Here are some tips on "reading" the seismogram plot. As an example, here is a seismogram for June 11, 2006, the day of the magnitude 6.3 quake on Kyushu. (Plotting parameters were: compression factor = 1, amplitude scaling = .004, and pixels between adjacent output traces = 5.)

a. The plot contains a series of traces. The y-axis shows the intensity of

ground motion, and the x-axis is time. b. Most of the traces in a random 24-hour plot will be flat; squiggles in the

traces indicate seismic activity. c. Each trace represents 15 minutes (900 s) of data. The first trace of each

hour is colored red. It is followed by three black traces—one for each of the remaining quarter-hours.

d. Look for the first sign of activity following the UTC time given for the earthquake. In this case, the time of the original earthquake was 20:01:29 UTC (= 20:00:00 hours plus 89 seconds). The first squiggle appears in the red trace at 20:00:00 hours + 810 s.

e. Thus, the elapsed time was 810 - 89 = 721 seconds (just over 12 minutes). f. If you are not sure that a squiggle is related to the earthquake you are

studying, try creating a plot for the same time period using one (or more) additional data station(s). This way you can confirm or reject your hunch.

3. Here are some tips on printing the seismogram. Since the plots are large, you probably won't have much luck printing directly from the browser window. Instead, save the plot as a file and print it with another program.

a. Right click on the plot, b. Choose Save Image As... to save image to file c. Then import into another program (e.g. Word) for printing.

4. Here are some tips if you have problems creating a seismogram. a. Data may not be available for all stations at all times, which means that

sometimes you may end up with an error message instead of the seismogram you were looking for. If you see an error message like: "Cannot create seismogram -- apparently there is no data.", try using another station. If that doesn't work, try selecting a different earthquake to study.

b. If you have a hard time seeing the individual traces in a plot, try decreasing the amplitude scaling by a factor 10. (You can also increase the number of pixels between adjacent output traces, but this will increase the vertical size of the plot.)

c. If these tips don't help solve your problem, try the help links on the Make Your Own Seismogram! page.

Calculate the Average Velocity of the Seismic Waves

1. velocity = distance / time 2. Calculate distance from epicenter to seismometer station using the latitude and

longitude of each point. Here's how: a. You already have the latitude and longitude of the epicenter of the quake

(step 4 of Select Historic Earthquakes to Analyze, above). b. You can find the latitude and longitude of each of the data stations in the

table, below. (Note that you can click on the data station code to see a webpage with detailed information about each station.)

Table 1. Make Your Own Seismogram! Station Locations

station code

latitude (decimal degrees)

longitude (decimal degrees)

elevation (m) place name

BDM +37.9540 -121.8655 +220 Black Diamond Mines Park, Antioch, CA, USA

BKS +37.8762 -122.2356 +244 Byerly Seismographic Vault, Berkeley, CA, USA

BRIB +37.9189 -122.1518 +220 Briones Reserve, Orinda, CA, USA

BRK +37.8735 -122.2610 +49 Haviland Hall, Berkeley, CA, USA

CMB +38.0346 -120.3865 +697 Columbia College, Columbia, CA, USA

CVS +38.3453 -122.4584 +295 Carmenet Vineyards, Sonoma, CA, USA

ELFS +40.6183 -120.7279 +1554 Eagle Lake Biol. Field Stn., Susanville, CA, USA

FARB +37.6978 -123.0011 -18 Farallon Islands, CA, USA

GASB +39.6547 -122.7160 +1355 Alder Springs, CA, USA

HATC +40.8173 -121.4705 +1009 Hat Creek Radio Astronomy Obs., Cassel, CA, USA

HELL +36.6801 -119.0228 +1140 Rademacher Property, Miramonte, CA, USA

HOPS +38.9935 -123.0723 +299 Hopland Field Station, Hopland, CA, USA

HUMO +42.6071 -122.9567 +555 Hull Mountain, OR, USA

JCC +40.8175 -124.0296 +27 Jacoby Creek, Bayside, CA, USA

JRSC +37.4037 -122.2387 +70 Jasper Ridge Biol. Preserve, Stanford, CA, USA

KCC +37.3236 -119.3187 +888 Kaiser Creek, CA, USA

MHC +37.3416 -121.6426 +1250 Lick Observatory, Mt. Hamilton, CA, USA

MNRC +38.8787 -122.4428 +710 McLaughlin Mine, CA, USA

MOD +41.9025 -120.3029 +1554 Modoc Plateau, CA, USA

ORV +39.5545 -121.5004 +335 Oroville Dam, Oroville, CA, USA

PACP +37.0080 -121.2870 +844 Pacheco Peak, CA, USA

PKD +35.9452 -120.5416 +583 Bear Valley Ranch, Parkfield, CA, USA

RAMR +35.6360 -120.8698 +417 Ramage Ranch, Paso Robles, CA, USA

SAO +36.7640 -121.4472 +317 San Andreas Geophysical Obs., Hollister, CA, USA

SUTB +39.2291 -121.7861 +252 Sutter Buttes, CA, USA

WDC +40.5799 -122.5411 +268 Whiskeytown Dam, Whiskeytown, CA, USA

WENL +37.6221 -121.7570 +139 Wente Vineyards, Livermore, CA, USA

YBH +41.7320 -122.7104 +1060 Yreka Blue Horn Mine, Yreka, CA, USA

c. Use the online calculator, Surface Distance Between Two Points of Latitude and Longitude (Byers, 1997), to find the distance between the epicenter of the earthquake and the data station.

d. The calculator requires you to enter the latitude and longitude in degrees, minutes seconds, instead of decimal degrees. However, it has a handy converter you can use. Click on the button that says, "Decimal Degrees <=> Deg Min Sec". A popup window will open where you can convert from decimal degrees to degrees, minutes and seconds.

e. Enter the latitude of the epicenter in decimal degrees, and click on the "Converts to" button (see screenshot below).

f. Now go back to the distance calculator and enter the latitude of the

epicenter in degrees, minutes and seconds. g. Repeat for the longitude of the epicenter, and the latitude and longitude of

the data station (see screenshot, following the next step). (Note that a positive value of latitude is North of the equator, and a negative value is South of the equator. For longitude, a positive value is East of the prime meridian and a negative value is West of the prime meridian.)

h. Once you have entered the latitude and longitude of both points, click on the "Distance between" point to calculate the distance (see screenshot, below).

i. The distance between the epicenter of the Kyushu earthquake and the BSK

data station is 9030 km. 3. Divide the distance by the elapsed time you calculated from the seismogram. For

our example, the distance is 9030 km, and the time is 721 s. The calculated velocity is 12.5 km/s.

4. Repeat all of above the steps for 10–20 earthquakes from (roughly) the same area of the world.

5. What is the average velocity of the seismic waves from the earthquakes you studied? (More advanced students should also calculate the standard deviation.)

Variations

• The seismometers measure shaking in three dimensions: vertically (up and down), north-south, and east-west. Do seismic waves in each of these dimensions travel at the same or different speeds?

• Speed vs. magnitude. Do seismic waves from more powerful earthquakes travel faster than those from less powerful earthquakes? Measure speed from ten earthquakes for each of several differnent magnitudes and compare.

• Interested in making your own seismograph? Try the Science Buddies project Is There a Whole Lot of Shaking Going On?

• You can also use the Make Your Own Seismogram! webpage to create hour-length seismograms using broadband channels, which are good for viewing local earthquakes. Is the seismic wave speed over shorter distances the same as that over larger distances? You can use the USGS website to locate historical earthquakes in northern California. In addition, for a list of recent earthquakes in the region, see http://www.ncedc.org/cgi-bin/finger-quake.

• For a more advanced project that uses seismometer data, try the Science Buddies project Locating the Epicenter of an Earthquake.

• Advanced. Design an experiment to see if there is a relationship between seismic wave speed and the geological features between the earthquake epicenter and the seismic recording station. For example, do seismic waves travel differently through oceanic crust vs. continental crust?

Pop Goes the Geyser! (from http://sciencebuddies.com/science-fair-

projects/project_ideas/Geo_p040.shtml?fave=no&isb=c2lkOjEsaWE6R2VvLHA6MSxyaWQ6MzI5MzU5MQ&from=TSW)

Objective To model a geyser and determine the effect that depth has on timing of geyser eruption. Introduction Visiting the U.S. national parks can be amazing and educational. Nearly every park is a display of the powerful geological forces that made this Earth. Yellowstone National Park in Wyoming is well known for its incredible geysers. A geyser is an opening in Earth's surface that periodically ejects hot water and steam. In fact, the word geyser is rooted in the Icelandic verb gjosa, which means "to gush."

The conditions required for geysers exist in only a few places on Earth, so are quite rare. Geysers are located near active volcanic areas, in proximity of magma. Three basic conditions must be met for geysers: there must be (1) a water supply, (2) a heat source, and (3) a reservoir and plumbing system. When you think of plumbing, you probably think of pipes in your house, but the plumbing system in Earth is made up of rock, which must be hard enough to withstand the intense pressure of superheated water. The configuration of the reservoir and plumbing can vary, but if all three conditions are not met, then geysers will not form. However, other geothermal activity could exist instead, like fumaroles and mudpots. There are two kinds of geysers, fountain geysers and cone geysers. Fountain geysers erupt from pools of water, while cone geysers erupt from cones, or mounds, of sinter. Fountain geysers are typically a series of intense bursts, while cone geysers are steady jets that

can last from a few seconds to a few minutes.

Figure 1. Castle Geyser in Yellowstone National Park. (Brantley, S.R., USGS, 1983.)

The source of water in a geyser can be a nearby river, rainfall, or circulating groundwater. Rainfall works its way underground through fractures in the rock. The water comes in contact with hot rock and then heats up. The water then rises back to the surface and comes into contact with rhyolite rock. Rhyolite rock is former volcanic ash, or lava, that is rich in silica. Silica dissolves from the rhyolite and precipitates as sinter, which, over time, forms the geyser cone and coats the plumbing system. As a result, the plumbing system hardens and becomes pressure-tight. As the geyser fills with water, the water at the top of the geyser cools down. The cooler water presses down on the hotter water beneath, which causes the water beneath to become superheated. Because the plumbing system is pressure-tight, the pressure of the superheated water is carried all the way to the top and does not leak out into the surrounding soil. As the superheated water nears the surface, its pressure drops and the water flashes and turns quickly into steam, expanding and lifting the water upward in an eruption. In this geology science fair project, you will build a model geyser and investigate how the depth of the water source affects the eruption of the geyser. Since you will be working with hot water, remember to wear safety goggles and perform the project away from other people. Have fun learning more about the powerful geologic forces that make up the planet Earth!

Figure 2. The cross-section of a cone geyser. (National Park Service, 2004.)

Terms, Concepts and Questions to Start Background Research

• Geyser • Reservoir • Superheating • Geothermal • Fumarole • Mudpot • Fountain geyser • Cone geyser • Rhyolite rock • Silica • Sinter

Questions

• What are the three factors that are required for a geyser to exist? • What causes pressure-tight geyser plumbing? • What is superheated water?

Bibliography

• Streepey, M. (1996, December 12). Geysers and the Earth's Plumbing Systems. Retrieved January 26, 2009, from http://www.umich.edu/~gs265/geysers.html

• Wikipedia Contributors. (2009, January 26). Geyser. Wikipedia The Free Encyclopedia. Retrieved January 26, 2009, from http://en.wikipedia.org/w/index.php?oldid=266603543

• National Park Service. (n.d.). How Geysers Work. Retrieved January 26, 2009, from http://www.nps.gov/archive/yell/tours/fountainpaint/geyser_works.htm

• Doherty, P. and Muller, E. (n.d.). Geyser: Cyclic hot water fountain. Retrieved January 26, 2009, from http://www.exploratorium.edu/snacks/geyser/index.html

Materials and Equipment

• Plastic pitcher, 2-quart (qt.) • Drill with a bit that has the same diameter as the glass tubing • Safety goggles • Rubber stopper with one central hole; available at your local science shop, or

online at sciencekit.com. Choose a size 10 stopper SKU # WW62856M10. • Glass tubing, 1 meter (m) long; available at your local science shop, or online at

sciencekit.com. Choose the 6-millimeter (mm) O.D. tubing, SKU # WW61975M76.

• Glass tubing, 0.5 m long. The 0.5-m-long tubing should be the same diameter as the 1-m-long tubing. You can have an adult help you use a pipe cutter to cut a 1-m length of glass tubing down to 0.5 m.

• Pipe cutter; available at your local hardware store • Erlenmeyer flask, 500 milliliters (mL); available at your local science shop or

online at sciencekit.com, SKU # WW61740M15 • Plumber's putty; available at your local hardware store • Single burner, portable and with temperature control; available online at

www.amazon.com • Ring stand; available at your local science shop or online at sciencekit.com, SKU #

WW63100M03 • Liquid measuring cup, 2-cup • Optional: Paper towels • Stopwatch • Lab notebook • Graph paper

Disclaimer: Science Buddies occasionally provides information (such as part numbers, supplier names, and supplier weblinks) to assist our users in locating specialty items for individual projects. The information is provided solely as a convenience to our users. We do our best to make sure that part numbers and descriptions are accurate when first listed. However, since part numbers do change as items are obsoleted or improved, please send us an email if you run across any parts that are no longer available. We also do our best to make sure that any listed supplier provides prompt, courteous service. Science Buddies receives no consideration, financial or otherwise, from suppliers for these listings. (The sole exception is any Amazon.com or Barnes&Noble.com link.) If you have any comments (positive or negative) related to purchases you've made for science fair projects from recommendations on our site, please let us know. Write to us at scibuddy@sciencebuddies.org. Experimental Procedure

1. Find a location with a table and an electrical outlet nearby. Try to find a location that is free of debris.

2. Put on your safety goggles. With an adult's help, drill a hole in the bottom center of the plastic container. The hole should be big enough for the glass tubing to be snugly inserted.

3. Now insert the 1-m glass tubing into the hole of the rubber stopper. Gently slide the tubing into the hole until it is flush with the bottom of the rubber stopper.

4. Fill the Erlenmeyer flask with 200 mL of water. Firmly insert the rubber stopper with the glass tubing into the Erlenmeyer flask. Try to reduce the gap between the flask neck and the stopper. You want to make sure that steam doesn't escape

from the flask. You can use a small amount of plumber's putty to seal the rubber stopper against the flask neck.

Figure 3. Rubber stopper with glass tubing sealed to the Erlenmeyer flask.

5. Place the burner on the floor and plug it in, but don't turn it on yet. Put the ring

stand together and position it on the table. See Figure 4, below. 6. Place the flask with the rubber stopper on the burner. 7. Slide a ring onto the ring stand, over the glass tubing. The ring should be

positioned several centimeters below the end of the glass tubing. Don't tighten the ring yet.

8. Carefully insert the end of the tubing through the hole in the bottom of the plastic container. Adjust the container so that the glass tubing extends a few centimeters above the bottom of the container, but well below the container's rim.

9. Adjust the metal ring so that it is supporting the plastic container. Now tighten the ring to the ring stand. The ring has to support the weight of the plastic container and several cups of water.

10. Take a small amount of plumber's putty and seal the glass tubing to the bottom of the plastic container.

11. Fill the measuring cup with cool tap water and carefully add the water to the plastic container. Fill the container with enough water that the top of the glass tubing is 2–3 centimeters (cm) below the surface of the water and the surface of the water is well below the rim of the container.

Figure 4. Example of a model geyser.

12. As you are pouring water into the container, some of the water will flow into the

Erlenmeyer flask below, through the glass tubing. Keep adding water to the container to maintain the water level at 2–3 centimeters (cm) above the top of

the glass tubing, as the water enters the flask below. Try to get as much water into the flask as possible, while keeping the water level in the plastic container at 2–3 cm above the top of the glass tubing. If you're having trouble getting water to flow into the flask, try gently tapping the glass tubing or container. Try to get the flask at least half full. The plastic container should have enough water in it to fill any free space left in the flask and the surface of the water should be 2–3 cm above the end of the glass tubing.

a. If some water spills from the container onto the burner, unplug the burner and use paper towels to wipe up the water from the burner and surrounding area. Be careful to not snap the glass tubing. Be gentle when you wipe up any water. Let the burner dry completely. Plug the burner back in when you are sure that there is no water in the burner.

13. Create a data table, like the one below, in your lab notebook.

Length of Glass Tubing = Total Number of Eruptions = Burner Setting =

Cycle Eruption Start Time Eruption End Time Duration of Eruption

Time Between Eruptions

Average: Average:

14. Turn the burner on. Do not leave the burner unattended. Note the setting of the burner in your lab notebook.

15. As the water in the flask heats up, you will notice the air in the glass tubing move up the tubing and bubbles pop into the water in the plastic container.

16. Eventually, after enough pressure has built up, the geyser will erupt. As soon as the geyser erupts, start your stopwatch. Record the start time in your lab notebook. Note the time on the stopwatch when the eruption ends in your data table, but do not stop the stopwatch. The eruption stops when the geyser resets itself by sucking cool water from the container into the flask.

17. Note down in your data table the time on the stopwatch when the next eruption occurs. Again, note down in your data table when the eruption ends.

18. Repeat step 17 until the container of water gets too hot and the difference in temperature between the container of water and the water in the flask is not

great enough to refill the system and erupt. Note down how many cycles you were able to get from this geyser model.

19. Turn the burner off and unplug it. Let the water in the container and flask cool down to room temperature. Repeat steps 13–18 two additional times, always remembering to record your data in your data table, and to let the water in the model cool down to room temperature between trials. If the water level in the container is not 2–3 cm above the top of the glass tube, then refill the container with water to the proper level.

20. After the model has cooled down completely, carefully remove the plastic container from the glass tubing. Immediately block the hole in the container to minimize the amount of water that spills out, and pour the water into the sink (or recycle it and use it to water your plants or for your next set of trials!). Peel off the plumber's putty from the Erlenmeyer flask. Replace the 1-m glass tubing with the 0.5-m tubing. Repeat steps 3–19. If possible, carefully move the model geyser from the floor to the table to accommodate the shorter tubing for these trials.

21. Using the data tables, calculate the duration of the eruption and the time between eruptions. To calculate the duration of the eruptions, subtract the start time from the end time. To calculate the time between eruptions, subtract the end of one cycle from the beginning of the next cycle. Calculate the average duration of an eruption and the average time between eruptions. Perform these calculations for each trial and for each length of tubing.

22. Now analyze your data. Plot your data. If you would like to learn more about plotting or would like to do your plots online try the following website: http://nces.ed.gov/nceskids/CreateAGraph/default.aspx. Plot the duration data on a scatter plot. Label the x-axis Tubing length and the y-axis Average duration. For this graph, plot the average for each trial. For each tubing length, there should be three data points. On a second scatter plot, label the x-axis Tubing length. and the y-axis Average time between eruptions. Do you notice any patterns in the data? Is there a difference in the eruption times between the 1-m glass tubing and the 0.5-m glass tubing? Is there a difference between the time between eruptions for the 1-m glass tubing and the 0.5-m glass tubing? If so, what is the cause (Hint: read the Exploratorium's science snack on geysers to find a clue)? How many eruptions occurred for the 1-m glass tubing? How many for the 0.5-m tubing?

Variations

• Repeat the science fair project with a smaller Erlenmeyer flask. • Repeat the science fair project with several different heat settings. • Change the diameter of the tubing and the diameter of the hole in the rubber

stopper.

Under Pressure: Sand Under Lateral Compression (from http://sciencebuddies.com/science-fair-

projects/project_ideas/Geo_p024.shtml?fave=no&isb=c2lkOjEsaWE6R2VvLHA6MyxyaWQ6MzI5MzU5MQ&from=TSW)

Objective The goal of this project is to investigate how layers of sand deform under lateral compression. Introduction If you've studied Earth science in school, you know that the surface of the Earth (the crust) is made up of many separate plates (Figure 1, below). These plates ride on top of the deeper, molten layer of the Earth, the mantle. You also learned that the plates are not stationary, but are slowly moving. What happens to the Earth's crust when tectonic plates collide? One result of the tremendous forces generated by movement of tectonic plates is the folding of the Earth's crust. For a quick demonstration, grasp a sheet of paper lengthwise with one hand at each end of the paper. Slowly push your hands together. The paper buckles, with the center either rising upward or extending downward as you bring the ends of the paper toward each other. Due to the tremendous pressures that can be created by plate movement, this kind of folding can occur with layers of rock. Geologists have names to describe the different types of folds. When the layers have just a slight bend, it's called a monocline. When the center of the fold rises up like an arch, the fold is called an anticline. When the center of the fold falls down in a trough, the fold is called a syncline. When the compression forces are very great, you can sometimes see multiple anticlines and synclines following one after the other. There are also more complex folds called recumbent folds ("recumbent" means "lying down"). As you might imagine, these are folds that have been "knocked over" by additional shearing forces. A reference in the Bibliography has example diagrams to illustrate each of the folding patterns described above (Pidwirny, 2007). It's a little hard to generate enough force to bend rocks with an apparatus that you can easily build in your garage, so for this project you'll be investigating layers made with different colors of sand instead of rock. For your experimental apparatus, you'll build a sandbox with a moveable piston to compress the sand (see Figure 2 in the Experimental Procedure).

To do the experiment, you first carefully load up the box with layers of sand, alternating two different colors to make the layers readily visible. Then you use the piston to apply a compressive force to the layers of sand. Transparent windows in the sides of the box allow you to see the resulting layering patterns after the compressive force has been applied. You can take successive pictures, or record with a video camera, to see how the patterns develop over time as the force is applied. The surface tension of water causes the grains of sand to stick to one another, so you could investigate the effect of changing the wetness of the sand used. Or, you could investigate the effects of changing the grain size of the sand used. Or, while you're doing the experiment, your own observations may lead to another avenue of exploration. Press on and find out!

Figure 1. Map of major tectonic plates of the earth. (Tilling, date unknown). Terms, Concepts and Questions to Start Background Research To do this project, you should do research that enables you to understand the following terms and concepts:

• Structure of sand • Compression • Plate tectonics

• Crustal folding o Monocline o Syncline o Anticline o Recumbent fold

Questions

• Will folding patterns be affected by the grain size of the sand used? • Will folding patterns be affected by the wetness of the sand used?

Bibliography

• For background on the processes of folding and faulting, see: • Pidwirny, M., 2007. "Crustal Deformation Processes: Folding and Faulting,"

PhysicalGeography.net [accessed June 21, 2007] http://www.physicalgeography.net/fundamentals/10l.html.

• For information on plate tectonics, see: o WGBH, 1998. "A Science Odyssey: You Try It: Plate Tectonics," WGBH,

Boston, and PBSOnline [accessed June 21, 2007] http://www.pbs.org/wgbh/aso/tryit/tectonics/intro.html.

o Kious, W.J. and R.I. Tilling, 1996. "This Dynamic Earth: The Story of Plate Tectonics," U.S. Geological Survey [accessed June 21, 2007] http://pubs.usgs.gov/gip/dynamic/dynamic.html.

o USGS, 2003. "Plate Tectonics and Sea-Floor Spreading," Cascades Volcano Observatory, U.S. Geological Survey [accessed June 21, 2007] http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/description_plate_tectonics.html.

• Here's some good background information on the structure of sand: Armstrong, W.P., . "Sand Grains: Chips Off the Old Rock," Wayne's Word, An Online Textbook of Natural History [accessed June, 21 2007] http://waynesword.palomar.edu/ww0704b.htm.

• If you want to make your own colored sand, here is a way to do it with food coloring. (You'll need to dry out the sand afterwards, so plan ahead to allow extra time to complete your project.): About.com, date unknown. "How To Color Sand," About.com [accessed June 21, 2007] http://goflorida.about.com/c/ht/01/05/How_Color_Sand0991160651.htm.

• To cut the Plexiglass plastic for the side window(s), you can score the material and then snap it off. Here's how to do it: DIY.com, 2007. "Plexiglass Cutting," DoItYourself.com Community Forum

[accessed June 21, 2007] http://forum.doityourself.com/archive/index.php/t-67920.html.

• This project is based on the following webpage: Indiana School for the Deaf, date unknown. "Sandbox Compression Experiments," Indiana School for the Deaf, Indianapolis, IN [accessed June 21, 2007] http://www.deafhoosiers.com/sci/soarhigh/sandbox/SandboxCompression.htm.

Materials and Equipment To do this experiment you will need the following materials and equipment:

• Tools: o Table saw, circular saw, or hand saw for cutting plywood o Router, sabre saw, or coping saw to make cut-out(s) in sides for viewing o Power drill and drill bits (including pilot bit for wood screws) o Plexiglass/acrylic scoring tool o Straightedge

• Half sheet (4' × 4') of 3/4" plywood • 1/4" or 3/16" thick transparent Plexiglass/Lexan/acrylic material for sides • Length of 1/2" threaded rod for applying lateral pressure • Mounting hardware for threaded rod • Strip of sheet metal (for "scraper" at bottom of piston) • Box of #10 wood screws (for assembling sand box) • Camera and/or video camera • Tripod • Sand

o You'll need some colored sand to make visible layers. You can find this at art/hobby stores or online. One online source is Blick Art Materials.

o You can experiment with dry sand vs. wet sand. Experimental Procedure

1. Use the photograph below as a guide for building the sandbox. The exact dimensions are not critical.

Experimental apparatus for compressing layers of sand. (Indiana School for the Deaf, date unknown)

2. Here are some tips for the construction:

a. The brace at the right side of the box (yellow arrows) needs to be sturdily mounted.

b. Naturally, it will be important to make sure that all of the corners are nice and square.

c. The piston needs to fit snugly against the plastic sides. d. Attach a flat strip of sheet metal at the bottom of the front face of the

piston. It should be flush with the bottom of the piston. The sheet metal will act as a "scraper" to keep sand from slipping underneath the piston. The photograph below shows how much sand was left behind before the sheet metal strip was installed.

Before a sheet metal "scraper" was installed at the bottom surface of the piston a lot of sand could "leak" under the piston as it moved. (Indiana School for the Deaf, date unknown)

e. In the design shown, there is a nut mounted inside the brace at the right hand side. The crank is turned, which rotates the threaded rod, and advances it through the nut. The threaded rod pushes the piston to compress the sand. At the piston end, the threaded rod is mounted in a metal bushing, which holds the rod in place but allows it to turn.

3. For each experiment, you'll need to carefully load the box with sand, alternating layers of different colors. Here are some ideas for you to try (remember to change only one variable at a time):

a. Vary the wetness of the sand. b. Vary the coarseness of the sand.

4. Advance the piston by turning the threaded rod. 5. Use a video camera to record the results, or take still photographs at regular

intervals. a. For photographs, you will probably get better results if you turn the

camera's flash off. This will avoid glaring reflections from the Plexiglass windows. If you are shooting indoors, you will probably need a tripod (or other sturdy support for the camera) so that the shot is not blurry.

b. You may want to take separate photographs showing both side views and top views of the sand (see below):

Side view of sand compression apparatus in action (Indiana School for the Deaf, date unknown).

Top view of sand compression apparatus in action (Indiana School for the Deaf, date unknown).

6. As with any scientific experiment, you should run repeated trials with the same conditions to verify that your results are consistent.

7. What layering patterns do you see? For example, do you see any examples of: a. monoclines? b. synclines? c. anticlines? d. recumbent folds?

8. What similarities persist across the various experimental conditions you tried? 9. What differences did you notice? 10. Advanced. Can you explain how the force of the piston is transmitted through the

sand to create the folding patterns in the layers? Variations

• Try using sands with various grades of coarseness. You should be able to find different grades at your local hardware or building supply store.

• What happens if the pressure is applied back-and-forth instead of steadily advancing?

• If you want to get really fancy, you may even want to consider modifying the apparatus to use a hydraulic drive for the piston. You should be able to better

control of the speed of the motion, and you may have the ability to increase the speed of the motion this way. What effect do the dynamics of the motion have on the layers of sand?

• Note: the following idea has not been tested, so it may or may not work. You might try using layers of more solid materials to see if faulting would occur and what patterns would result. You might try thin layers of plaster, or cement without sand in it. For these harder materials, you would probably need to use two threaded rods to apply sufficient pressure to the piston. A potential drawback of this project idea is that the materials you are testing may prove to be more durable than your box, in which case it will be the box that breaks instead of the test material. You will definitely want to wear safety glasses, in case any bits of material go flying.

Underground Water Flow and Darcy's Law (from http://sciencebuddies.com/science-fair-

projects/project_ideas/Geo_p014.shtml?fave=no&isb=c2lkOjEsaWE6R2VvLHA6MixyaWQ6MzI5MzU5MQ&from=TSW)

Objective The goal of this project is to model the flow of groundwater, and to calculate the flow rate using Darcy's formula. Introduction Fresh water exists not only in lakes and streams on the surface of the earth, but also underground. These subsurface sources of freshwater are called underground aquifers, and the water in them is called groundwater. Like water on the surface, groundwater can also flow. And like water on the surface, groundwater also flows downhill. Groundwater can also move in response to differences in pressure from the overlying rock, soil, and water. The rate of groundwater flow will also depend on the material through which the water is flowing. Materials that are more solid will reduce the flow rate, while materials that are more porous will increase the flow rate. Darcy's Law is a relationship that explains fluid flow in porous media, such as often seen in geological formations. The basic formula to calculate the flow rate, Q, is: Q = KA (h1 − h2) / L where:

• K is a permeability coefficient (describes the porosity of the underground formation),

• A is the cross sectional area, • h1 is the height of the inlet head, • h2 is the height of the outlet head, and • L is the path length of the flow.

Understanding how groundwater moves is important for predicting how quickly underground aquifers will be replenished when water is drawn up from wells drilled down from the surface. Sometimes groundwater can become tainted with salt water or even toxic compounds seeping from a contaminated source. In these cases it is especially important to understand groundwater movement, in order to contain the spread and prevent contamination of aquifers used for drinking water or irrigation.

In this project, you will use plastic soda bottles to make models of water flowing through underground formations. You will fill the bottles with different materials (e.g., sand, gravel, silty clay, etc.) and then measure water flow to see the effects of different types of formations. You can investigate the effects of pressure by making outlets at different heights on the bottle. The height of the water above the outlet creates the pressure, so the lower the outlet is, the more pressure there will be. By measuring the flow rate at the outlet, you can see how well Darcy's Law predicts your results. Terms, Concepts and Questions to Start Background Research To do this project, you should do research that enables you to understand the following terms and concepts:

• groundwater, • aquifer, • porosity, • Darcy's Law, • artesian well, • drawdown.

Bibliography These websites will help you get started with your background research on groundwater and Darcy's Law:

• Mullen, K., 2006. "Darcy's Law," National Groundwater Association [accessed November 30, 2006] http://www.ngwa.org/educator/lessonplans/darcy.cfm.

• SDSU, date unknown. "Applying Darcy's Law to a Confined Aquifer," San Diego State University, Department of Geological Sciences [accessed November 30, 2006] http://www.geology.sdsu.edu/classes/geol351/darcys.htm.

• Wikipedia contributors, 2006. "Darcy's Law," Wikipedia, The Free Encyclopedia [accessed November 30, 2006] http://en.wikipedia.org/w/index.php?title=Darcy%27s_law&oldid=87395188.

• water table draw-down animation: GROW, 2004. "Water Table Drawdown," Geotechnical, Rock and Water Resources Library [accessed November 30, 2006] http://www.grow.arizona.edu/Grow--GrowResources.php?ResourceId=168.

Materials and Equipment To do this experiment you will need the following materials and equipment:

• 4 (or more) 2 L plastic bottles, • plastic tubing (e.g., aquarium tubing, drinking straw), • sharp knife, • modeling clay, • large measuring cup or graduated beaker for measuring outflow, • timer or stopwatch, • material to simulate subsurface, e.g.:

o pea gravel, o aquarium gravel, o sand, o clay soil, o mixtures of clay and sand.

Experimental Procedure

1. Do your background research and make sure that you are knowledgeable about the terms, concepts, and questions, above.

2. Prepare at least four 2 L bottles for measuring flow rates, as described in Figure 1, below:

Figure 1. Each soda bottle should have a single outlet hole. Make four bottles, each with an outlet hole at a different height. To collect the outflow, connect a short length of drinking straw or aquarium tubing to the outlet hole, and seal the edges with modeling clay. Use a large measuring cup or other graduated container to catch the outflow. (Thanks to John LeVasseur for the soda bottle drawing from which this diagram was adapted.)

3. To investigate the effect of pressure on underground water flow, compare the flow rate from the different outlet holes. Fill each bottle with the same medium (e.g., sand).

o Keep the water level in the bottle constant by pouring water in at the top. o Measure the outflow by collecting the water in a graduated container and

measuring how much water you collect in a given time period (e.g., 10, 20, or 30 seconds).

o Convert your flow rate to liters per minute for comparing the different conditions.

o Calculate the pressure head for each condition by measuring the difference between the heights of the inlet (h1) and outlet (h2). The arrows in Figure 2 show the pressure head (h1 − h2) for each of the outlet holes.

o Graph your results by plotting flow rate (y-axis) vs. delta h (the inlet height minus the outlet height, as shown in Figure 1). How well does Darcy's Law predict your results?

4. To investigate the effect of different materials on underground water flow, use different materials to fill the bottles. Compare the measured flow rates for the different materials (using outlets at the same height). Can you use Darcy's Law to calculate the K value (permeability coefficient) for each material?

Variations

• What do you think will happen to flow rate if you change the diameter of the bottle? Can you relate this change to groundwater movement?

• What do you think will happen to the flow rate if you change the diameter of the outlet tubing?