How the Grand Canyon (大峡谷) was created remains one of the geology's greatest mysteries. Some evidence suggests that the process was a gradual one in which the Colorado River (which runs through the canyon) slowly cut deeper and deeper into the ground over millions of years. But volcanic rock samples taken from the canyon now suggest that the canyon was down-cut instead.

    Down-cutting is when a flood of water rushes over a landscape (地形) with enough force to cut deeply into the ground and leaves behind a canyon. Such a flood is usually released when a natural or man-made dam (堤坝) bursts.

    Robert Webb, a research geologist, says natural dams seem to have formed and broken across the Colorado River several times during the last million years. The dams were built when lava(熔岩) from the eruptions of nearby volcanoes flowed into the river. The lava hardened into hard rocks and blocked the river, causing it to back up and form a lake. Each time the lake grew so huge that it broke the rock dam, releasing a flash flood that furthered the down-cutting process and deepened the canyon.

    Down-cutting is not just an earthly event. Satellite photos sent back from Mars suggest that the process has happened there, too, say many other researchers.

    The photos, taken by the Mars Global Surveyor, indicate that an enormous lake existed on Mars 3.5 billion years ago. The lake spilled into a large nearby hole. One edge of the hole broke, releasing a flash flood that quickly carved out a grand canyon.

    The existence of down-cutting on Mars is just one more piece of evidence that the cold, dry planet was once warm and wet.

    For 80 years, Macy's Thanksgiving Day Parade has kicked off the holiday season with glorious bands, balloons and floats (花车)，and for one day, it has transformed New York City into a living comic book.

    The Macy's Thanksgiving Day Parade is an annual parade presented by Macy's Department Store. It was first held in 1924. It was organized by Macy's employees, most of whom were first­ generation immigrants(移民)，who wanted to celebrate holidays like they did in Europe. The employees dressed in costumes(盛装)and marched on the streets with floats, bands and live animals borrowed from a zoo.

    With an audience of over a quarter of a million people, the parade was such a success that Macy's declared it would become an annual event.

    In 1927 Felix, the Cat became the first parade balloon to float over the city. Large animal­ shaped balloons replaced the live animals from then on. These giant signature(特有的)balloons are by far the biggest attraction of the parade. Each year sees parade balloons adding new characters from comic strip characters to timeless toys.

    One tradition long gone is the releasing of the balloons after the parade. They would float for days and the lucky finder or finders could claim a cash reward if he or she returned the balloon or its remains to Macy's.

    The parade has gone on every year except during World War Ⅱ when, aside from not having much to cheer about, the helium(氦气)air and rubber used for the balloons were needed for the war effort.

    When the parade returned in 1945，it was televised in New York for the first time and also traveled its current route for the first time.

    Nowadays, more than 10,000 people participate in the parade and the National Broadcasting Company(NBC) will nationwide broadcast it live from 9 a.m. to noon. The NBC has even earned several Emmy Awards for this program.

    As always, the parade will end with a visit from Santa Claus. The joyful old man will get settled in Macy's Department Store after the parade to start a­month­long search for who's been naughty and who's been nice.

    To above prices, please add $3 for first book and $1 for each additional book for postage & handling. Foreign countries add $5 per book. Send orders to Quackwatch, P. O. Box 1747, Allen Avenue, NY 18105. The checks must be in US dollars. We cannot process credit card orders. Please use our order form from Amazon.com and include your email address.

    To help the environment, many Americans have made the change from paper and plastic(塑料的) bags to reusable shopping bags. But a report by a Florida newspaper says that reusable shopping bags sold by some supermarkets have high levels of lead (铅), which can be dangerous to humans, especially young children. Now, there's a call for a rethink about the use of reusable shopping bags.

    “When our families go to the store looking for safe and healthy foods, the last thing they should be worrying about is a bag,” Charles Schumer, a government official said.“ Quick and complete research will allow everyone to make right decisions.”

    The newspaper bought more than a dozen bags sold at Publix supermarkets from Florida supermarkets to test them for lead. The results showed that certain bags had lead levels that worried health officials. Some bags had enough lead in them to be considered dangerous waste if people were to throw the bags out with other rubbish. Lead in the bags may not move onto food. But over time, paint on the bags can break off and the bags can wear out. When this happens, lead can be freed.

    The bags with the highest levels of lead had beautiful designs and many pictures. Plain （朴实无华的） reusable bags without them are found to have little lead. People worried about lead levels in reusable bags can turn to cloth. Paper bags are also a good choice, since paper can be reused.

    Christmas is a great time with family and friends. One of the best ways to bond with (团结)one another is through games. So why not play some great Christmas party games?

    Present pickup is a great game for both young and young at heart. It can be played inside or outside. To prepare for the game, you will need to have some small boxes and some small gift bags. This is a great way to use the paper from last year. There should be as many presents as players. You'll also need four or more candy canes(甘蔗). Two large boxes can be used to drop the presents in.

    Two ropes will be needed. Take one rope and make a starting line. The other rope will mark the finish line. Place the large boxes at the finish line. Equally divide the presents into two groups. It's best to have an equal number of boxes and bags on each side to make it fair.

    The first player on each team will take two candy canes. When it's time to start, they'll pick up the presents only using the candy canes. Each player must run his present to the box or finish line and drop it in. If it's dropped on the way, the player starts over. After they drop their presents, the players will run the candy canes to the next players. This continues until all the presents have been picked up. The first team to finish wins.

    To play kids against adults, you may want to put easier presents in a group for the kids and more difficult ones for the adults. There are many variations to the game, so have some fun and come up with your own.

    The world is a greener place than it was 20 years ago. A study published in the journal “Nature Sustainability” said that recent satellite data reveals a greening pattern that is strikingly prominent in China and India. The study shows that human activity in China and India dominates this greening of the planet, thanks to tree planting and agriculture. The effect comes mostly from ambitious tree-planting programs in China and intensive agriculture in both countries.

    “China and India account for one-third of the greening,” said lead author Chi Chen of Boston University. “ That is a surprising finding, considering the vague idea of land degradation (毁坏) in populous countries from overexploitation,” added Chen.

    China alone accounts for 25 percent of the global net increase in leaf area with only 6.6 percent of global vegetated area. The greening in China is from forests (42 percent) and croplands (32 percent), but in India, it is mostly from croplands (82 percent) with minor contribution from forests (4.4 percent).

    China's outsized contribution to the global greening trend comes in large part from its programs to conserve and expand forests with the goal of preventing land degradation, air pollution, and climate change.

    “Once people realize there is a problem, they tend to fix it,” said Rama Nemani, research scientist and co-author of the study. “In the 1970s and 80s in India and China, the situation around vegetation loss was not good. In the 1990s, people realized it, and today things have improved. Now we see that humans are contributing.”

    Land area used to grow crops is comparable in China and India—more than 770, 000 square miles—and has not changed much since the early 2000s. Yet these regions have greatly increased both their annual total green leaf area and their food production.

    This was achieved through multiple cropping practices, where a field is replanted to produce another harvest several times a year. Production of grains, vegetables, fruits and more have increased by about 35%～40% since 2000 to feed their large populations.