Coincidence in the Ring of Fire?

EarthView students know that the island nation of Indonesia -- the world's fourth-most populous country -- is located on the Pacific Ring of Fire. 

The eruption and the earthquake that triggered the tsunami this week occurred 800 miles apart, affecting two separate islands -- Java and Sumatra. They may be related, as have similarly distant events in the past, such as an Alaska earthquake and geyser activity in Yellowstone, Wyoming. Indonesia is the most tectonically active place on Earth, however, so it will be some time before a connection can be proven or discounted.

Learn more about this week's tragedies and the possible connections from National Geographic magazine.

National Geographic photo of damage from 2004 tsunami

Gordon Mitchell School, East Bridgewater -- October 22

42° 01' 50" N
70° 56' 43" W
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The EarthView team is delighted to be returning to the Gordon W. Mitchell School in neighboring East Bridgewater, Massachusetts, which the team last visited in 2009. In fact, two Mitchell students are close family friends of team member Dr. Hayes-Bohanan.

The school is located very close to a site known as Sachem Rock, where the original conveyance of land from the Wampanoag Indians to Miles Standish in 1651. This land became the town of Bridgewater in 1656, and that town was eventually divided into what we now know as seven different cities and towns. In some ways, this was the beginning of the westward expansion of what would become the United States.

During the visit, the team was accompanied by Kiado Cruz, a farmer and activist from Chiapas, Mexico, and his team from Witness for Peace. They gave a presentation on the importance of local agriculture at Bridgewater State University on October 21 as part of a New England tour of schools, churches, and civic organizations. Although Kiado, Nikky, and Susan did not have a chance to visit with Mitchell students, they did have an opportunity to see the world from the inside, and to contemplate their own important work in a global context.

Drying Lakes

Lake Chad images (1972 and 1987)
 as posted Waterless on the Town Square blog

EarthView is a terrific learning tool, whether viewed from inside or out. During today's program at the Ahern Middle School, a student looking at north-central Africa from outside asked about the body of water surrounded by dry land. What she was noticing was Lake Chad, which was once the sixth-largest lake in the world but had already lost a considerable amount of its surface area by the time EarthView was painted in the 1990s. In that sense it is much like the Aral Sea, which long ago surrendered its status as the world's fourth-largest lake, and which the EarthView artist represented with a similar, broad fringe of dry land.

Both lakes are found in arid or semi-arid lands, and are shared by multiple countries -- Nigeria, Niger, Chad, and Cameroon in the first case and Kazakhstan and Uzbekistan in the latter. Moreover, in the case of the Aral Sea, lands in four additional countries contributed directly to the drainage area of the sea.

Image from the Fire Earth blog

Growing or shrinking lakes represent shifts in the water balance for the watersheds (also known as drainage basins) in which they are found. Lakes can shrink as a result of water use that exceeds rainfall in the basin as a whole. This in turn can affect habitat in and near the lake, the availability of irrigation or drinking water, and even the regional climate.

Both of these shrinking lakes are excellent examples of the use of satellite images to monitor lakes. The  United State Geological Survey  (USGS) includes both Lake Chad and the Aral Sea in its EarthShot series, which documents many other examples of the uses of remote sensing. The Visualizing Earth project at UC-San Diego has a similar Aral Sea page that -- like the EarthShots pages -- allows users to move between satellite and ground-level images.

For decades to come, Lake Chad and the Aral Sea will remain reminders of how seriously humans can damage the natural environments on which we depend. Despite the bad news, some positive steps are being taken: international bodies are working together to protect the wetlands of Lake Chad and a new dam is helping to increase the flow of water to the Aral Sea. People in many countries have much more to do, however, if these lakes are to be fully restored!

Ahern Middle School - Foxborough - October 15

42° 4' 27" N
71° 14' 18" W
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The John J. Ahern Middle School in Foxborough is hosting the EarthView team for the third time in the program's three years. A lot has happened with EarthView and with the Geography Department that runs the program  since the first visit in 2008.
For example, the department is no longer part of Bridgewater State College -- it is now part of Bridgewater State UNIVERSITY, a teaching university that will continue to serve the region. Second, the department -- formerly in the School of Arts & Sciences -- is now part of the university's new School of Science & Mathematics.  Geography is both a social and a physical science, connected to the other so-called STEM disciplines.
The EarthView team is particularly interested to learn that Ahern will soon have a family math night. We will be sharing ideas with Ahern teachers about ways to include geographic fun in that event!
To learn more about what EarthView has achieved over the past three years and what still lies ahead, the team invites you to scroll through the blog -- which now has close to 100 articles about school visits, geographic education, and some fascinating stories of our planet!

Circle of Illumination

WORLD SUNLIGHT MAP

In the hallway outside the Geography Department office at Bridgewater State University is a fascinating device known as Geochron. Manufactured decades ago, it is a combination map and clock that is configured so that it always represents the areas of the earth in sunlight and darkness. At all times, exactly one half of the earth is illuminated by the sun, though cloud cover can affect how much reaches the surface and latitude can influence its intensity. The 50 percent in sunlight is known as the circle of illumination, because the boundary between sunlight and darkness forms a circle.

On the equinoxes, the circle of illumination intersects both the north and south poles, but during the rest of the year, the circle appears tilted first one way and then another, as the earth orbits the sun at a constant 23.5-degree angle. During this orbit, the apparent position of the sun changes steadily, and it appears directly overhead at only one place at a time on the planet. That location is known as the sub-solar point, and it oscillates from the Tropic of Cancer on the summer solstice to the Tropic of Capricorn on the winter solstice (as defined in the northern hemisphere -- people in the south use the opposite terminology).

On the original, mechanical Geochron, a small dot represents the single place on earth -- always in the tropics -- where the sun appears to be directly overhead. Of course, there is only one such point at any time, known as the sub-solar point because it appears to be under the sun.It moves from the Tropic of Cancer on our summer solstice to the Tropic of Cancer on our winter solstice, crossing the equator on the equinoxes.

Two digital versions of the GeoChron are readily available online. The World Sunlight Map shown above also represents current cloud cover and is available in several different projections. The NIST version from the National Institute of Standards is accompanied by the current, official time as used for U.S. Government purposes. (Be sure to adjust the time zone or display options if necessary.)

With parental permission, it is also now possible to install a miniature version of the GeoChron as a desktop gadget on your computer, allowing you to track the sun at all times.

We invite EarthView participants to view the mechanical GeoChron in our geography department, in order to see the circle of illumination in more detail and to marvel at the clever, compact design. On the mechanical version, it is also possible to see how the sun's noon position advances and retreats through the year not only by latitude but also by longitude, tracing the figure-eight shape of the analemma.

World Daylight Clock on Your Desktop

The circle of illumination always lights half of the earth's surface, with the other half left in darkness and a thin band of twilight in between. You can check the digital version of GeoChron on the EarthView blog throughout the year to learn how the illuminated area changes through the seasons. You can also -- with parental permission -- install the World Daylight Clock (a Google Gadget) on your desktop to watch the progress of the sun minute-by-minute.

I captured the image above just a couple minutes ago, while writing this article. It shows that my home in Bridgewater is about to rotate into the circle of illumination, and indeed it is twighlight outside my window.