Letters from the March 5, 2005, issue of Science News

Way-up wander?

It seems interesting that undersea flows have at least one characteristic different from rivers: “While river floods on land can create natural levees a few meters tall, the levees formed by [undersea] turbidity currents can grow up to 100 m[eters] high” (“Hidden Canyons,” SN: 1/1/05, p. 9). There are several sites on Mars where channels with loops can be seen. Although the processes may be much different, it would be interesting to compare the height and relative size of the depositions within Mars’ channels—rivers versus undersea canyons.

John Gilbert
Pasadena, Calif.

What’s up?

“Tsunami Disaster: Scientists model the big quake and its consequences” (SN: 1/8/05, p. 19) has a graphic that appears to show an area that lifted by up to 5 meters and a vaguely equal area that was depressed by up to 2 m. This suggests an average increase in the distance of mass from the center of Earth. Yet a researcher claims that Earth’s rotation time has decreased. What am I missing?

Bob Williams
Los Alamos, N.M.

The graph shows the vertical displacement of the seafloor, most of which occurred on the Burma tectonic plate. In some places, several kilometers beneath the seafloor, the India tectonic plate slid downward as much as 20 meters—a phenomenon detectable only by the immense quantities of energy it released.—S. Perkins

Spuds spectacle

I envision a beautifully colorful potato salad utilizing multiple colors of potatoes (“Food Colorings: Pigments make fruits and veggies extra healthful,” SN: 1/8/05, p. 27). But would a cooked mixture be like carrots with potatoes (minimal bleed) or like beets with anything else (maximum bleed)?

Lorraine Bauder
Sudbury, Mass.

The red and blue pigments in the new potato lines are “water soluble and will leach,” notes USDA’s Charles R. Brown. However, unpeeled potatoes bleed minimally. Potatoes tinted yellow to orange shouldn’t bleed at all because their carotenoid pigments aren’t water soluble.—J. Raloff