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On Again, Off Again —
The Dead Zone

Activity #5
Building a Three-Dimensional Model of the Dead Zone
Student groups or whole class

Introduction/ Purpose:
Visualizing the dead zone in three dimensions is difficult. The phenomenon has a complex, irregular shape and has a wide range of depths, heights and widths. In this activity, a 3-D visual of the dead zone will be constructed. The following models are presented from the easiest to construct to the most complex.

Objective:
The students will:

• Construct a three-dimensional model of the dead zone.

Standards:

• Grades 6-8: N-8-M, M-2-M, M-6-M, G-4-M, G-7-M, D-1-M
• Grades 9-12: N-6-H, M-3-H, M-4-H, G-3-H, D-7-H
• Skills: Observing, measuring, communicating, defining operationally, interpreting data and formulating models

Notes:
In these activities, the dead zone can be modeled with or without the perspective of depth and location within the entire water column.

Map size/scale:
Map size for these activities should be 11”x17" or larger.

Vertical scale:
Wooden skewers or straws will represent the water column at each data station in models 1-3. A scale of 5 mm = 1m works well with a 10" (255 mm) skewer if the entire water column is considered. For example, a 20m station would be represented by 100mm of skewer. Label the water surface at the top as “0" and the station depth as the bottom of the gulf.

The area below the gulf bottom on the skewer represents the subsurface. The maximum depths for all of the stations for this data set range from 17-53 m and the minimum ranges from 2-24 m.

Expand the vertical scale to about 10mm = 1m to model the dead zone only (without the whole water column perspective).

Simple 3-D Model #1

This model represents a general 3-D shape. The data required for this model are for the stations that are located on the perimeter of the dead zone.

Materials:

• 3 copies (11" x 17" or larger) of map developed in Activity #4 with transect/stations labeled
• Sheet of styrofoam or a copy paper box with lid to serve as a secure base for the map
• 10" wooden shish kabob skewers (22-100)
• Blue, black and red felt tip markers or paint
• Colored paper
• Calculator
• Garden clippers (optional)
• Paper
• Pencils
• Tape flags

Procedure:
Prepare map base:

1. Determine a map size/scale and enlarge map from Activity #4 to fit desired scale.
2. Attach the station map to the styrofoam sheet or inverted box with pins or tacks.
3. Place the colored sheet of paper over the map. This will represent the Gulf bottom.
4. Cut out two of the plotted dead zone polygons from Activity #4 and label one “top” and the other “bottom.”
5. Place the two cut-out polygons of the hypoxic zone over the map with the one labeled “top” on the top. Be sure to line up the stations.

Prepare water column:

6. Construct a data table for the perimeter stations identified in Activity #4. Include transect, station number, bottom depth and maximum and minimum depth of hypoxic zone for each station. Include two columns for recording scale model depth calculations, one each for the top and the bottom of the dead zone.
7. Determine a vertical scale for the skewers to depict depth (see notes).
8. Convert vertical depth of the dead zone to the model scale and record in the data table.
9. Label transect and station number on each skewer with a marker or a ‘flag’ taped at the top.
10. Mark the bottom depth in black at each station/skewer. Begin measurements at 0" from the flat surface of the skewer (representing the water surface).
11. Mark the maximum and minimum depth of the hypoxic zone on each station/skewer in red. Note: In many cases the bottom depth and the maximum depth of the dead zone will be the same. Optional: Color or paint the portion of the skewer below the bottom mark black, the area above the bottom to the top of the dead zone in red, and the area above the top of the hypoxic zone blue. These colors represent the sediments below the gulf bottom (black), the hypoxic zone (red) and the remainder of the water column (blue).

Putting it together:

12. Insert skewers at station site through all four layers of the map keeping the tops of the skewers even. This is the water surface.
13. Raise the polygon labeled “top” to the top of the dead zone mark at each station.* This represents the upper boundary of the dead zone in the water column.
14. Raise the “bottom” polygon to the bottom of the dead zone mark at each station.* This represents the lower boundary of the dead zone in the water column.
15. Raise the colored paper to the bottom depth mark (sea floor bottom) at each station.* This represents the sea floor bottom and below represents sediment below the gulf bottom.
16. View your model from several angles/sides and complete the questions for the Activity #5.

Notes
* The paper may become too tight between stations where depth of the dead zone changes quickly. Extend paper by cutting and then taping additional sections as needed to ease the layer.

For modeling the dead zone only, follow Steps 1-6 expanding the vertical scale. Insert skewers at each station stopping at the Gulf bottom mark. Clip off the excess skewer below the sea bottom if necessary. Complete Steps 8-16 and disregard references to the water surface.

Simple 3-D Model #2

This model is made by connecting all/or some of the interior stations with thread or string. All station data are required for this model. This model will show some contour and irregularities between stations.

Materials:

• One enlarged (at least 11"x17") copy of map created in Activity #4.
• Data table from Activity #4
• Sheet of styrofoam or copy paper box with lid to fit map size
• 10" wooden shish kabob skewers
• Blue, black and red felt-tip markers or paint
• String or embroidery thread (two colors)
• Calculator
• Paper and pencils
• Tape flags
• Optional: small/tiny rubber bands such as those used on braces

Procedure:
Prepare map base:

1. Determine scale and enlarge map from Activity #4. The more interior stations that are used, the greater the map scale/size should be.
2. Determine which stations will be used to represent the dead zone. Choose the stations on the perimeter (Activity #4) and several interior stations that can be handled with the size of the model.
3. Attach the map to styrofoam sheet with pins or tacks.

Prepare the water column:

4. Construct a data table for all stations, include transect, station, depth and maximum and minimum depth of dead zone for each station. Include two columns for recording scale model depth calculations–one for the top and another for the bottom of the dead zone depth.
5. Determine a vertical scale to be used on the skewers to depict depth (see notes).
6. Convert the vertical distance (depths) to model scale and record in the data table.
7. Label station and transect number on each skewer (a labeled flag of tape works well).
8. Mark bottom depth and maximum and minimum depths of the dead zone on each station skewer. Begin measurements at 0" from the flat surface of the skewer (representing the water surface).
9. Color or paint the portion of the skewer below the bottom mark black, the area above the bottom to the top of the dead zone in red, and the area above the top of the hypoxic zone blue. These colors represent the sediments below the gulf bottom (black), the hypoxic zone (red) and the remainder of the water column (blue).
10. Attach rubber band onto each skewer at the maximum and minimum depths of the dead zone. This will help keep the thread from slipping. Optional.

Putting it together:

11. Insert skewers at each station site on the map keeping the tops of the skewers even. This is the water surface.
12. Delineate the Gulf bottom by using one color thread. Tie thread/string at bottom mark of one skewer and move to an adjacent station and wrap the thread around the skewer at the bottom mark. Continue weaving around other stations to delineate the
13. Delineate the dead zone with a second color. Tie thread/string at top of the dead zone of one skewer and move to an adjacent station and wrap thread around the skewer at the top of the dead zone mark. Continue weaving around stations and between tops and bottoms, forming a web between stations and depth to a desired density for shape.
14. View your model from several angles/sides and complete the questions for the Activity #5.

For modeling the dead zone only, follow Steps 1-10, expanding the vertical scale. Insert skewers at each station stopping at the gulf bottom mark. Clip off the excess skewer below the sea bottom if necessary. Complete Steps 12-14.

3-D Model #3

This model is made by connecting all/or some of the interior stations with clay. This model will show some contour and irregularities between stations.

Materials:

• One enlarged (at least 11"x17") copy of map created in Activity #4, laminate if possible.
• Data table from Activity #4
• Sheet of styrofoam or copy paper box with top to fit map size
  10" wooden shish kabob skewers
• Clay or Model Magic
• Blue, black, red felt-tip pens
• Calculator
• Paper, pencils
• Garden clippers (optional)
• Tape flags

Procedure:
Prepare a base map:

1. Determine scale and enlarge map from Activity #4. The more interior stations that are used, the greater the map scale/size should be.
2. Determine which stations will be used to represent the dead zone. Choose the stations on the perimeter from Activity #4 and several interior stations that can be handled with the size of the model.
3. Attach the map to styrofoam sheet or inverted cardboard box with pins or tacks.

Prepare the water column:

4. Construct a data table for all stations, include transect, station number, station depth, depth and maximum and minimum depth of hypoxic zone for each station and add two columns for scale model depth calculations.
5. Determine a vertical scale to be used on the skewers to depict depth (see notes).
6. Convert the vertical distance (depths) to model scale and record in the data table.
7. Label station number on skewers (a labeled flag of tape works well).
8. Mark bottom depth and maximum and minimum depths of the dead zone on each station leaving enough skewer to secure in styrofoam “gulf bottom” (at least 0.5-1").
9. Color or paint the portion of the skewer below the bottom mark black or brown, the area above the bottom to the top of the dead zone in red, and the area above the top of the hypoxic zone blue. These colors represent the sediments below the gulf bottom (black or brown), the hypoxic zone (red) and the remainder of the water column (blue). Optional

Putting it together:

10. Insert skewers at station sites on the map and cardboard/styrofoam to the gulf bottom mark. The water surface will be uneven.
11. Build clay around the sticks to create the bottom surface interpolating between stations and using the top and bottom of the dead zone to determine thickness of clay.
12. Observe the model from several angles and complete the questions for Activity #5.

Note:
A solid model can be built by securing the skewers into the cardboard base, keeping the top of the skewers even. The sea floor and subsurface is formed first. This clay base of the subsurface and sea floor can illustrate the irregular topography of the sea floor before the dead zone is constructed over it. After the subsurface and sea floor is constructed, change color of clay and build the dead zone using the bottom and top markings on the skewers. To further utilize the model, cut cross sections in different areas of the model, compare a cross section at each transect with those that have been graphed. Cut a cross section between transects and one parallel to the shoreline to observe the differences.

For modeling the dead zone only, expand the vertical scale and follow Steps 1-8. Insert skewers at each station stopping at the gulf bottom mark. Optional: clip off the excess skewer above the top of the dead zone and complete Steps 11-12 working the clay.

The height of the dead zone can be measured from the pointed tip of the skewer up and the skewer can be secured on the map with a lump of clay and then built up for the model.

3-D Model #4

This large-scale model uses students or stakes to represent the portion of the water column that is hypoxic. The class will determine distance between stations and height of the dead zone to a scale that will utilize the available space in a room or field.

Materials:

• Map from Activity #4 or a Louisiana offshore map with stations marked
• Large room or field
• Boundary and station markers
• Data table developed in Activity #4, Models 2 and 3
• Wooden or metal poles or stakes
• Black crepe paper, surveyor tape or twine
• Paper, pencils
• Calculator

Procedure:
Prepare map base:

1. Determine map scale for the model.
2. Convert distance between stations to model scale and record on a table.
3. Mark area boundaries in room or field and determine a vertical and horizontal scale of the map location and for the water column for example 1m = 1km on the ground.
4. Mark and label each station on students and/or poles.

Prepare Water Column:

5. Determine a vertical scale to be used on the students and/or the poles.
6. Construct a data sheet for all stations, include transect, station number and maximum and minimum depth of hypoxic zone for each station and add two columns for scale model, one for height of the dead zone (difference between maximum and minimum depth of dead zone) and one for the scale model height.
7. Calculate the distance between the top and the bottom of the dead zone from the station data and record in the data table.
8. Convert the vertical distance (depths) to model scale and record in the data table.
9. Mark the top and bottom of the dead zone on each pole/student. The gulf bottom will be represented by the floor or ground in the model.
10. Students take their place at their stations on the project area with their top and bottom locations visible.
11. A few students will join the students/pole water columns, stations and transects together with string or crepe paper at the top and bottom of the hypoxic zone from their feet up their legs, forming the top and bottom boundary of the dead zone.
12. Observe the model from several angles and complete the questions for Activity #5.

Note:
For a small class, the 3-D model can be reduced in size by using fewer transects and modeling only a section 2 or 3 transects of the dead zone and using pole for the entire model.

Questions for Activity #5 3-D model:

1. Estimate the volume of the dead zone.
2. Estimate the percentage of the study area volume that is hypoxic.
3. Predict how you expect the model to change by September.
4. What would cause the dead zone to decrease in size? What would cause an increase in size?
5. Where would you expect conditions to change first with a small storm? Why?
6. State some reasons why the dead zone is “deeper” and “wider” in some areas?
7. What kinds of weather events do you think could change DO, temperature and density in the water column and why would that happen?

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