Updated 9/10/13

In Podcast #62 the Trekkers take you two two of Virginia’s natural wonders, the Natural Bridge and the Natural Tunnel. They were both produced by water weathering and eroding the limestone rock, but they are very different from each other.  We’ve already been to the Natural Bridge in Podcast #13 but this time we wanted to film it with our HD camera. Find out which natural wonder is the biggest; visit a replica of a Monacan Indian village and see how they lived; discover a man-made wonder near the Natural Bridge called Foamhenge (a replica of Britain’s Stonehenge); learn why a rock formation near the Natural Tunnel is called Lovers’ Leap; and see whether David really called Alfonso a baboon. Come on, let’s go trekking!

The Natural Tunnel and Natural Bridge were mined for saltpeter, an essential ingredient of gunpowder, during the Civil War.  Limestone caves in the Appalachian mountains were important sources of saltpeter for the Confederacy, especially since the Union blockade prevented them from importing gunpowder.  Saltpeter was mined by mixing soil from the caves with water in large wooden vats called hoopers.  The minerals in the soil were absorbed into the water, making a solution.  This solution was then boiled in huge cast-iron kettles and mixed with potash or lye (a substance made from ashes). The white powder that remained after all the water evaporated was called saltpeter (from Latin sal petrae or “salt of rock”).  The chemical formula for saltpeter is KNO3, potassium nitrate.  Finally, the saltpeter was sent to gunpowder manufacturers where it was mixed with sulphur and charcoal to make gunpowder.

(Source1, Source 2, Source3)

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SOL Correlation:


K.2 The student will describe everyday life in the present and in the past and begin to recognize that things change over time.


2.3 The student will identify and compare changes in community life over time in terms of buildings, jobs, transportation, and population.


2.7 The student will investigate and understand that weather and seasonal changes affect plants, animals, and their surroundings. Key concepts include

  1. b)weathering and erosion of land surfaces.


4.9 The student will investigate and understand important Virginia natural resources. Key concepts include

a) watersheds and water resources;

  1. b)animals and plants;

  2. c)minerals, rocks, ores, and energy sources; and

  3. d)forests, soil, and land.


VS.2b The student will demonstrate knowledge of the physical geography and native peoples, past and present, of Virginia by locating and describing Virginia’s Coastal Plain (Tidewater), Piedmont, Blue Ridge Mountains, Valley and Ridge, and Appalachian Plateau.


VS.2d The student will demonstrate knowledge of the physical geography and native peoples, past and present, of Virginia by locating three American Indian language groups (the Algonquian, the Siouan, and the Iroquoian) on a map of Virginia.


VS.10b The student will demonstrate knowledge of government, geography, and economics by describing the major products and industries of Virginia’s five geographic regions.


Valley & Ridge

Saltpeter looks like salt

A wooden saltpeter hooper

Kettle for boiling saltpeter

Ingredients of gunpowder