Chalk is good for drawing with. But did you know that it's also good for drawing in?

Formed from the shells of tiny marine creatures, natural chalk--as opposed to the manufactured kind you find in classrooms--is a soft, porous variety of limestone. About 144 million years ago, large chalk deposits began forming in parts of the United States and Europe.

Because of their white color, these deposits have created some striking geological formations, such as the chalk cliffs that form the coast off the town of Dover in England. (Fun historical fact: Those cliffs were the inspiration for the World War II-era song "There’ll Be Bluebirds Over the White Cliffs of Dover." Annoyingly pragmatic follow-up fact: There are no bluebirds in England.)

England's giant chalk formations have led to some giant artwork--especially in the county of Wiltshire, two-thirds of which lies on chalk. For reasons that aren't entirely clear, in the 18th and 19th centuries people in Wiltshire began carving enormous white horse figures into hills. They usually accomplished this by cutting away the soil to expose the white chalk beneath, then putting loose chalk back into the areas they had cut out. The results were huge, dramatic forms that could be seen from miles away.

Eight of Wiltshire's white horses still exist, and the people who live nearby are proud of them and work hard to keep them in good shape. Because the chalk horses are part of the countryside, they quickly become overgrown with vegetation and disappear unless they're maintained regularly.

The most famous white horse of all, however, lies just over the county line in Oxfordshire. Whereas the chalk horses of Wiltshire are only a couple of hundred years old, the horse in Oxfordshire--known as the Uffington Horse--has been dated to 1400 BCE. That means people have been keeping it in good shape for more than 3,000 years.

TRUSTED WEBSITES For more information on Wiltshire’s white horses, including photos and a timeline showing when each was created, click here. For serious Anglophiles only: a British geography quiz from the BBC. Click here.

		1. Lapis lazuli: The pigment made from this semi-precious stone was so expensive that painters who used it in commissioned pieces of artwork sometimes charged their clients extra.			A. Black
		2. Cochineal insects: It takes about 70,000 of these tiny creatures to make just one pound of dye!			B. White
		3. Charcoal: You might be more used to burning this in a grill than drawing with it--it’s both a fuel and an art material.			C. Orange-brown
		4. Lead: This metal was once used both in painting and as a cosmetic. Unfortunately, it’s poisonous either way.			D. Blue.
		5. Madder plant: Cloth colored with the dye from this plant has been found on the mummies of ancient Egyptians.			E. Red
		6. Sienna clay: The name of this clay (and the pigment it produces) comes from the town of Sienna, Italy.			F. Pink

. . . About the Struggle to Save This Cave?
We have four French teenagers to thank for the discovery of some of the most ancient artwork in the world. In 1940, the group of boys stumbled upon an opening to a complex of caves near Montignac, France. Painted on the walls of the caves were prehistoric drawings of animals that would prove to date back some 17,000 years. In comparison, the Uffington Horse (see above) is just a newcomer!

Soon people were flocking to the caves, now called Lascaux. And soon the warmth of so many bodies, plus the carbon dioxide they exhaled, began damaging the caves and their ancient artwork. In 1963, Lascaux was closed to the public. The caves’ climate stabilized again, and it seemed as if all was well. For the next several decades, only a very small number of people were allowed into Lascaux, and those only by special permission.

Then, in 2001, a little fungus called Fusarium solani came along. Possibly introduced to Lascaux via a new air conditioning system, the white fungus grew quickly on the cave walls. Caves are fragile and complex ecosystems, and changing just one factor--such as air flow--can result in widespread damage.

The caves' caretakers managed to get Fusarium solani under control with fungicides and antibiotics, but then another, black fungus popped up. In the summer of 2008, the situation remained so dire that the United Nations Educational, Scientific and Cultural Organization threatened to place Lascaux on its list of endangered world heritage sites.

Earlier this year, however, a cave official announced that while Lascaux's invasion by fungus hasn't gotten any better, it also hasn’t gotten any worse. "The cave is sick and is currently resting," he said. "We want the patient to recover and restore its natural balance by itself." Will this "patient" someday return to full health? Or will we lose one of our most precious artistic and archaeological treasures?

TRUSTED WEBSITES How do caves form, anyway? Find out with this animation from NOVA. Click here. What prehistoric cultures created art, and when? This interactive, illustrated timeline from the Metropolitan Museum of Art will show you. Click here.

October 2, 1950
Whether your favorite is Snoopy, Lucy, Charlie Brown, or the little red-headed girl, you--along with 355 million other readers--know Peanuts. The long-running, super-popular strip makes its very first newspaper appearance today.

October 4, 1861
American artist Frederic Remington is born on this day in New York. Despite his Eastern roots, he becomes one of the most famous artists specializing in subjects related to the Old West. Yippee ki-yay!

October 25, 1881
Today is the birthday of Pablo Diego Jose Francisco de Paula Juan Nepomuceno María de los Remedios Cipriano de la Santísima Trinidad Ruiz y Picasso--but you can just call him Picasso (or Pablo, if you and he go waaaay back). Born on this day in Malaga, Spain, he becomes one of the 20th century's most famous artists.

October 28, 1886
She may be full-figured, but she's fabulous: The 305-foot-tall Statue of Liberty, a gift from the people of France, is unveiled today in New York Harbor.

October 31, 1941
It's hard to say what's more impressive: that sculptor Gutzon Borglum and 400 workers used dynamite and other tools to carve four 60-foot faces of American presidents into the side of a mountain, or that nobody died doing it. That famous American icon, Mount Rushmore, is completed on this day in South Dakota.

October 31, 1632
If you've read Girl with a Pearl Earring (or seen the movie), you know who we're talking about: Artist Johannes Vermeer is baptized today in the Netherlands.