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Friday, May 12, 2017

Rumney Marsh Academy, Revere -- May 12

42º 24' 47" N
71º 00' 12" W

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Rumney Marsh Academy is a school that the EarthView team enjoys visiting each year, because students there study geography throughout the year. It is especially fun to arrive late in the school year, when the geography learning among sixth graders has been going on for months!

Visit our 2016 Rumney-Marsh post and earlier posts for information about our previous visits and about the marsh (wetland) for which the school is named. You can also read about its nearest neighbor -- a famous candy company. How many middle school students are lucky enough to be across the street from a candy factory? It is like Willy Wonka, but in real life.

Water Volumes

Our visits inside of EarthView always begin with a discussion of the Earth's water, and the fact that the vast majority of it is in forms (saltwater or ice) that humans cannot use for drinking, bathing, irrigation, or industry. We have this discussion in terms of percentages, but today a student asked what the total volume of the water would be. "Millions of cubic miles," we said, promising to look up the actual figures.

According to the United States Geological Survey (USGS), the volume of water on the earth is 332,500,000 cubic miles (mi3), or 1,386,000,000 cubic kilometers (km3). The image below shows what the earth would look like if all of the water were removed from oceans, ground water, streams, and lakes.
The largest blue sphere represents all of the water on earth. The smaller sphere -- situated over Kentucky in the United States -- represents only the liquid, fresh water. The tiniest sphere of all -- a dot that appears to rest on Georgia -- represents all of the surface water. Of that, about 20 percent is in the Amazon River Basin, and another 20 percent is in Lake Baikal in Russia. Learn more at the USGS How Much Water? page.

NEW (May 30, 2017): Speaking about this with the geography teachers at our EarthView Institute, we realized that we can update our presentation about water to include not only percentages, but also the absolute volumes of the various ways water is stored. Using the USGS site mentioned above and refreshing our memory of sphere-related formulae with the sphere calculator page, we created a new spreadsheet detailing earth's water at an EarthView scale. For example, we learned that all of the fresh liquid water at or above the earth's surface could fit inside a ping-pong ball at the scale of EarthView!

South-Up Map

We also spent a lot of time at our Hobo-Dyer-Mead map learning about the importance of relative size. An interesting way to learn more is to use the TrueSize web site, which allows viewers to select a country or U.S. state, and visually drag it to other parts of the world for comparison.
The "Lower 48" portion of the United States, for example, is about the size of Brazil. Often, the familiar Mercator projection gives us the wrong idea of the relative size of places.

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