IS ALASKA’S COASTLINE DISAPPEARING?
Overview
In this suite of activities, learners will measure coastal
erosion along the north coast of Alaska using NASA satellite
images taken 20 years apart.
Exposed ice-rich permafrost near
Cape Halkett, AK (left) courtesy
Benjamin Jones and Christopher
Arp, U.S. Geological Survey,
Alaska Science Center.
Contents
Activity 1: Compare Two Landsat Satellite Images of Cape Halkett . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Activity 2: Find the Difference Between the Two Satellite Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Activity 3: Add Scale and Measure the Distance from the Old to the New Coastline . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Activity 4: Measure the Rate of Erosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Extension Activity 1: Measure the Area and Volume of Erosion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Extension Activity 2: Calculate the Amount of Carbon Released from Coastal Erosion . . . . . . . . . . . . . . . . . . . . . . . . 13
Background Information: ImageJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Background Information: The Landsat Satellite Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Lesson Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Lesson References and Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Easy as 1 - 2 - 3 How to Download images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Objectives
In interlinked step-by-step lesson activities, the learner will:
1. compare two Landsat satellite images of Cape Halkett, along the north coast of Alaska;
2. find the difference between the two images;
3. add scale to the images to measure the distance between the old and new coastlines; and
4. calculate the rate of erosion.
Two extension activities describe how to:
1. calculate the area and volume of coastline eroded; and
2. calculate the amount of carbon released from the permafrost.
Materials
•
•
Landsat satellite images: (http://www.cryosphericconnection.org/satellite_images.html)
A computer with the application ImageJ downloaded
(Download ImageJ at http://rsbweb.nih.gov/ij/download.html. For instructions on how to download ImageJ, see
“Easy as 1-2-3: How to Download and Install ImageJ” on the Cryospheric Connection website:
www.CryosphericConnection.org/resources, under Application Downloads.)
Next Steps
ImageJ is easy to use and includes simpler versions of tools that scientists use to measure land features in satellite images.
The Cryospheric Connection Satellite Image Database (http://www.cryosphericconnection.org/satellite_images.html)
provides pairs of satellite and aerial images of lakes, rivers, and coastline in permafrost-rich areas of Alaska. These images
could be used for similar exercises, lessons, or assessments.
Cryospheric Connection ©2010 - 2012 Geophysical Institute, UAF
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Is Alaska’s Coastline Disappearing?
IS ALASKA’S COASTLINE DISAPPEARING?
Lesson Activity 1
Compare Two Landsat Satellite Images of Cape Halkett (page 1 of 3)
Activity Description
Compare the changes to the Cape Halkett coastline from 1985 to 2005 using two Landsat images.
Three steps will show how to open the images and how to zoom in to the coast.
STEP 1.
Download the two satellite images of Cape Halkett to your desktop from the Cryospheric Connection
website (www.CryosphericConnection.org/satellite_images.html).
STEP 2.
Open the ImageJ application. From the ImageJ File menu, choose
File → Open to open the images: Halkett_1985_432.tif and
Halkett_2005_432.tif.
STEP 3.
Zoom in to the northern coastline of both images. Click on the magnifying glass
on the toolbar, then click on the image to zoom in.
To zoom out, press the control key down while clicking the image. Use the scrolling (hand) tool to
move the image.
To illustrate this step, screenshots for the 2005 image are shown. Open and zoom in to both the
1985 and 2005 images to compare them. Leave the images open to move on to the next activity.
2005 Landsat image of Cape Halkett, AK
2005 Landsat image zoomed in to the coast
Image courtesy NASA Goddard Space Flight Center
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Lesson Activity 1
Compare Two Landsat Satellite Images of Cape Halkett (page 2 of 3)
Stop and Think
Look First: What changes can be observed between the 1985 and 2005 coastlines?
Answer:
For beginners it takes practice to look at satellite images. Look carefully along the coastline. Compare the
two images.
To the naked eye, some of the coastline appears to have changed. For example, notice how the land
separating the large lake from the sea at the left side of the zoomed-in area has changed. Also notice the
lake that has opened up to the ocean between 1985 and 2005.
*Note: Leave the image files open to move on to the next activity.
Cryospheric Connection ©2010 - 2012 Geophysical Institute, UAF
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Lesson Activity 1
Compare Two Landsat Satellite Images of Cape Halkett (page 3 of 3)
The Big Picture: The Impacts of Coastal Erosion
People and Animals
The rapid rate of coastal erosion affects the future of
communities on the coast. Cultural sites can disappear
into the sea. Animals’ habitats are affected. This area is
home to endangered and threatened waterfowl. Large
herds of caribou use the plain as calving grounds.
Oil and Gas
The North Slope of Alaska is also being studied for
future oil and gas development. The J.W. Dalton
petroleum test well that was drilled in the late 1970’s
near the coast has been lost to coastal erosion. Soon
the test well at Drew Point will be lost. Learning more
about coastal erosion is important for future oil and gas
explorations.
Greenhouse Gases
When the coast erodes, organic matter that has been
frozen for thousands of years is exposed. This material
can now decay or be consumed by microbes. In this
way, it turns into carbon dioxide or methane. These
gases are potent greenhouse gases that can increase
global warming.
Photos courtesy Benjamin Jones and Christopher Arp, U.S.
Geological Survey, Alaska Science Center.
Image courtesy U.S. Geological Servey
Cryospheric Connection ©2010 - 2012 Geophysical Institute, UAF
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Lesson Activity 2
Find the Difference Between the Two Satellite Images (page 1 of 2)
Activity Description
In this activity, changes to the coast between 1985 and 2005 will be made easier to see.
Two steps will show how to use the image calculator to make calculations. In this activity, the Difference function
is used to show areas of change. The Subtract function could also be used.
*Note: Work with the same images from Activity 1 (Halkett_1985_432.tif and Halkett_2005_432.tif). Zoom in as
shown in Activity 1.
STEP 1.
From the ImageJ menu, select Process → Image Calculator.
STEP 2.
From the dialog box, use the drop down menus to show the difference
between the 1985 image and the 2005 image. The dialog box should
look like the one below.
Click OK when finished.
The resulting image should look like the one pictured below. Leave the image files open
to move on to the next activity.
Cryospheric Connection ©2010 - 2012 Geophysical Institute, UAF
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Lesson Activity 2
Find the Difference Between the Two Satellite Images (page 2 of 2)
Stop and Think
Look First: What do the bright red areas along the north coast show?
Refer back to the 1985 and 2005 images to compare the same area.
Answer:
The red areas show the difference between the two images. This is the area that has been eroded over
the course of twenty years.
*Note: Leave the Result of Halkett_1985_432 image of this activity open to move on to complete the next activity.
The Big Picture: Summer Erosion, Cape Halkett, Alaska
Ben Jones and Christopher Arp, of the United States Geological Survey (USGS) Alaska Science Center, made a short
film of the erosion of the coast of Cape Halkett using a time-lapse camera. They rigged the camera up on top of a pipe
wedged into the sea floor off the coast. They took pictures of the coast every hour each day for just over a month. The
film is a compilation of a single photo from each day and shows loss over the course of the 2009 summer.
Find the film “Erosion of Cape Halkett, Alaska” on the Cryospheric Connection website under Videos at http://www.
CryosphericConnection.org/resources.html.
Courtesy Benjamin Jones and Christopher Arp, U.S. Geological Survey, Alaska Science Center.
Cryospheric Connection ©2010 - 2012 Geophysical Institute, UAF
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Lesson Activity 3
Add Scale and Measure the Distance from the Old to the New Coastline (page 1 of 2)
Activity Description
In this activity, scale will be added to the images to begin understand how much of the coast has eroded.
Four steps show how to measure the distance between the old coastline and the new coastline.
*Note: Activity 1 and 2 must be completed to move on to Activity 3. If you are starting here, work with the same
images from Activity 1, HALKETT_1985_432.tif and HALKETT_2005_432.tif. Zoom in as shown in Activity 1.
Find the difference between the two images as shown in Activity 2. Then begin Activity 3.
Without a scale bar in the image, it is hard to tell how much of the coast has been lost.
To help understand the scale, the Measurement tool can be used.
The basic steps of measurement are setting the scale, choosing the area to be measured,
taking the measurement, and then showing the results.
STEP 1.
From the ImageJ menu, select Analyze → Set Scale.
These Landsat images have a 30-meter resolution. That means that one pixel is 30
meters along an edge.
In the dialog box set the Distance in Pixels to 1 and the Known Distance to 30.
Change the Unit of length to m (meters). Select the “Global” box to apply the
scale to all the open images. Click OK when finished.
STEP 2.
Zoom in to the thermokarst lake circled in the image below.
STEP 3.
Select the Straight Line tool from the ImageJ toolbar.
Cryospheric Connection ©2010 - 2012 Geophysical Institute, UAF
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Lesson Activity 3
Add Scale and Measure the Distance from the Old to the New Coastline (page 2 of 2)
Step 3
Step 3
STEP 4.
Step 4
Click and drag a straight line from the edge of where the
coastline was in 1985 to where it was located in 2005. The
line should be perpendicular to the edge of the lake and to
the coast line.
STEP 5.
From the ImageJ menu, select Analyze → Measure.
A Results window will show the distance in meters in the Length column.
Step 5
Answer:The distance in this example is approximately 450 meters. The answer will vary depending on the length of the line.
Making Sense of the Number
The distance of 450 meters is about the length of four football fields set end to end. Remember, this is the distance
from the edge of the lake to the coast that has been eroded since 1985.
*Note: Save the answer from this activity to calculate the rate of erosion next in Activity 4. Keep the image open too.
The Big Picture: A Drained Lake
This figure shows the thermokarst lake just measured in
the activity. It compares the edge of the lake in a 1955
topographical map to 1985 and 2005 Landsat 5 satellite
images. The drainage of the lake and coastal flooding has
produced a new marine bay in the old lakebed.
Image courtesy U.S. Geological Survey.
Cryospheric Connection ©2010 - 2012 Geophysical Institute, UAF
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Lesson Activity 4
Measure the Rate of Erosion
Activity Description
In one step, find the annual rate of erosion.
*Note: Use the measurement from Activity 3 to make the calculation.
STEP 1.
Find the annual rate of erosion. For greater accuracy, several sections of eroded coastline could be measured,
then averaged.
Stop and Think
Think First: As a reminder the formula for calculating rate is: distance
time
or
d
t
Answer: 1. Divide the distance the coast has eroded by 20 (the number of years spanning the time between the two images):
450
2. The area north of this lake eroded approximately 22.5 meters per year.
_____
20
*Note: Leave the images of this activity open to move on to complete the next activity.
The Big Picture: The Rate of Erosion
Benjamin Jones, who works for the U.S. Geological
Survey Alaska Science Center, and his colleagues,
figured out a long-term mean erosion rate for the
entire cape of 7.6 meters per year between 19552009 and reported it in a paper about the erosion of
Cape Halkett. In their study, the scientists divided
Cape Halkett into three zones. The area used in
this exercise is in what they called the northeastfacing zone 1. It had a large increase in erosion
over the past few years. At the end of the 20th
century, erosion rates were as high as 14 meters
per year. At the start of the 21st century, erosion
rates for this zone went up to about 20 meters per
year. The calculations made in this activity come
close to what Jones and his colleagues found.
Cryospheric Connection ©2010 - 2012 Geophysical Institute, UAF
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Extension Activity 1
Measure the Area and Volume of Erosion (page 1 of 3)
Activity Description
In four steps, figure out how much of the coast has disappeared into the sea by calculating area and volume.
*Note: To complete this activity, the steps described in Activity 1 and 2 must be completed. If you are starting here,
work with the same images from Activity 1, HALKETT_1985_432.tif and HALKETT_2005_432.tif. Zoom in as
shown in Activity 1. Find the difference between the two images as shown in Activity 2. Then begin this activity.
The question still remains, how much actual earth has eroded? A little or a lot?
STEP 1.
Step 2
To calculate the area of coastline that has eroded, work with
the image that shows the difference between the 1985 and 2005
Landsat satellite images. From the toolbar click on the Polygon
selections tool.
STEP 2.
Step 1
Select an area on the image that shows
change. Click around the area. Close the
polygon by clicking on the starting point,
which appears as a square until clicked.
Step 3
STEP 3.
From the menu
select Analyze →
Measure.
Results will show
in a new window. Expand the window to see the
area measurement. The area will be in square
meters.
Answer:
In this example, 1,152,000 square meters of the coast are shown to have eroded from
1985 to 2005. Results will differ based on
the shape of the polygon that is drawn.
Cryospheric Connection ©2010 - 2012 Geophysical Institute, UAF
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Extensions Activity 1
Measure the Area and Volume of Erosion (page 2 of 3)
Making Sense of the Number
The surface area lost measures about half a square mile, an area 1 mile x .5 mile. This would be 210 football fields.
1,152,000 square meters / 5,390 square meters (the area of a football field) = 210.
The surface area of other parts of the coast can also be measured. A scientist would take careful measurements of
the whole area to get the best measurement.
Step 4 describes how to calculate the volume of this area. Volume
describes a three dimensional measurement, quantifying how much
soil a hand or a container could hold, for example.
STEP 4.
To calculate the volume, the height of the coastal plain
must first be determined by someone measuring it on
location.
In this area the height is approximately 2.2 meters.
Now, calculate the volume. See Hint 1 for a reminder of
the formula for volume.
Researcher Benjamin Jones measures the height of
a bluff on the north coast of Alaska. Photo courtesy
Benjamin Jones and Christopher Arp, U.S. Geological
Survey, Alaska Science Center.
Hint 1: The formula for finding volume requires the measurement of all three sides of an object: length, width, and height.
A good trick to remember how to find volume is to remember that volume has three dimensions. Area has two
dimensions. In this case, the area (length and width) of the polygon was calculated by the ImageJ application in
the previous activity.
Answer: To find the volume of coastline lost, multiply the area in square meters by the height of the bluff,
2.2 meters. Volume = length x width x height.
In this example, the answer would be 1,130,400 m2 x 2.2 m = 2,534,400 m3.
Cryospheric Connection ©2010 - 2012 Geophysical Institute, UAF
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Extensions Activity 1
Measure the Area and Volume of Erosion (page 3 of 3)
Making Sense of the Number
Measured by volume, the fourth-largest building in the world is the NASA Kennedy
Space Center Vehicle Assembly Building (VAB), in Florida. The volume of the VAB
is 3.6 million cubic meters (m3).
The total volume of soil eroded from this part of Cape Halkett between 1985 and 2005
was about 2.5 million m3. If the soil were put into the VAB, how much would it fill?
To find the answer, divide the volume of the soil by the volume of the building,
2,534,400 / 3,660,000.
NASA Kennedy Space Center photo.
What eroded off of the cape is equal to .69 or 69% of what the VAB could hold. If all
the material that eroded were put into the VAB, it would be about two-thirds full.
The Big Picture: Why is the Coast of the North Slope of Alaska Receding?
Less sea ice and earlier melting of sea ice in the spring have increased the wave action against the shore. The thawing
of permafrost makes it easier to erode the coast. Along this area, for example, the permafrost warmed by 4 degrees
between 1977 and 2003, from -10.1 degrees Celsius to -6.4 degrees Celsius. The temperature is measured as far
down as seasonal flux no longer affects the permafrost, about 15m in this case.
Interestingly, the original land feature named “Cape Halkett” no longer exists, though the name still refers to the
area in general. Cape Halkett was named during the Dease and Simpson expedition of 1837. Dease described it in
his journal as an island where they landed to have breakfast. He noted, “Here again are vestiges of Esquimaux having
worked wood & Killed Rein Deer. Some pieces of the Antler found about appear to have been sawed off with a regular
Saw.” Dease marked the location as “Lat. 70° 48’ N, Long. 151° 55’W.” Find the location in Google Earth.
The location of Cape Halkett, AK in 1837. Image courtesy Google Earth.
Cryospheric Connection ©2010 - 2012 Geophysical Institute, UAF
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Extension Activity 2
Calculate the Amount of Carbon Released from Coastal Erosion (page 1 of 2)
Activity Description
In four steps, calculate how much carbon was released from the coastline.
*Note: To complete this extension activity, work with the same images from the previous activities: Activity 1,
HALKETT_1985_432.tif and HALKETT_2005_432.tif. Zoom in as shown in Activity 1. Find the difference between
the two images as shown in Activity 2. Then begin the extension activity.
How much carbon was released from this area due to erosion?
STEP 1.
From the ImageJ tools select the Segmented
Lines tool. Right click (on a PC) or
Command click (on a Mac) to select the
Segmented Lines option.
STEP 2.
Zoom into an area that has been heavily
eroded. Use the segmented line tool to click
along the coastline that was still there in 1985.
Without moving the mouse, double click to
end the line. To delete a line, click on the image
to make it disappear. The nodes, or vertexes,
can be moved by clicking and dragging.
STEP 3.
From the ImageJ menu select Analyze → Measure.
STEP 4.
In the Results window, the length of the segmented line will be in meters.
In this example, the length of the section along the coast that has been lost to erosion is
about 4100 meters. Convert the meters to kilometers.
Hint: Divide the results by 1000 to convert meters to kilometers.
Answer: 4.1 kilometers
STEP 5.
From fieldwork conducted in this area, scientists have determined that the amount of carbon input from the
North Cape Halkett coastline is 605 Mg/km/yr, as mentioned above. A Mg, or megagram, is a metric ton.
Multiply the length (in km) x 605 to find the amount of carbon released in one year (in Mg/yr).
In this example, 4.1km x 605 Mg/km/yr = 2,480.5 Mg/yr.
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Extension Activity 2
Calculating the Amount of Carbon Released from Coastal Erosion (page 2 of 2)
Making Sense of the Number
How much carbon has been released, a little or a lot? How many railroad cars would it take to hold that amount of
carbon?
One railroad train car carries approximately 105 tons of coal. There is more than one way to figure out how many
railroad cars it would take to haul the carbon released from this area of Cape Halkett.
One way is to use Google to convert tons to metric tons: 105 tons is equal to 95.25 metric tons. So, one train car carries
about 95.25 metric tons of coal. To figure out how many total cars are needed, divide 2541Mg / 95.25 Mg per railroad
car = 26.6 railroad cars. Twenty six railroad cars full of coal weigh as much as the carbon released.
The Big Picture: Carbon in The Soil
In these photos the organic material in the soil that has eroded from the side of the bluffs can be seen. Researcher Ben Jones is pictured assessing the
site. The peat that erodes is often so thick that the researcher has to wade through it boot-deep. Photos courtesy Benjamin Jones and Christopher
Arp, U.S. Geological Survey, Alaska Science Center.
Carbon is frozen and trapped within permafrost where it has been stored for thousands of years along the north
coast of Alaska. While frozen, it is not an active part of the natural cycle. As permafrost thaws or slumps into
the ocean, carbon is released into the environment. Microbes can start to digest this carbon, thereby producing
carbon dioxide or methane.
What are the effects of carbon being released from its frozen state?
When carbon is released from frozen soil, organic matter breaks down into simpler forms more quickly. When
organic matter decays or is consumed by microbes, more carbon dioxide and methane are released. As more
carbon dioxide and methane are released, global temperatures rise. Both carbon dioxide and methane are
greenhouse gases. These gases trap heat, which results in global warming.
How do scientists determine how much carbon the soil contains?
To determine carbon and mineral content being released by thawing permafrost, scientists do fieldwork to
measure the amount of carbon in the soil. This can be done a number of different ways. Often, a scientist will
gather a sample of exposed permafrost and take it back to the lab to analyze. A LECO analyzer is often used
for this task. In the analyzer, which looks like a small refrigerator, a sample of material is combusted at a high
temperature. As gases pass through a tube, sensors measure the amount of each element in the sample.
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