Miscellaneous Data for the United States: Highest point:Mount McKinley, Alaska20,320 ft. (6,198 m) Lowest point:Death Valley, Calif.282 ft. (86 m) below sea level Approximate mean elevation2,500 ft. (763 m) Points farthest apart(50 states): Log Point, Elliot Key, Fla., and Kure Island, Hawaii5,859 mi. (9,429 km) Geographic center(50 states): in Butte County, S.D. (west of Castle Rock)44°58'N lat.103°46'W long. Geographic center(48 conterminous states): in Smith County, Kan. (near Lebanon)39°50'N lat. 98°35'W long. Boundaries: Between Alaska and Canada1,538 mi. (2,475 km) Between the 48 conterminous states and Canada (incl. the Great Lakes)3,987 mi. (6,416 km) Between the United States and Mexico1,933 mi. (3,111 km) Source:U.S. Geological Survey.

Extreme Points of the United States (50 States): Distance1 Extreme pointLatitudeLongitudemi.km Northernmost point: Point Barrow, Alaska71°23' N156°29' W2,5074,034 Easternmost point: West Quoddy Head, Maine44°49' N66°57' W1,7882,997 Southernmost point: Ka Lae (South Cape), Hawaii18°55' N155°41' W3,4635,573 Westernmost point: Cape Wrangell, Alaska (Attu Island)52°55' N172°27' E3,6255,833 1. From geographic center of United States (incl. Alaska and Hawaii), west of Castle Rock, S.D., 44°58' lat., 103°46' W long. If measured from the prime meridian in Greenwich, England, Cape Wrangell, Attu Island, Alaska, would be the easternmost point.

How Old Is the Grand Canyon?: The Grand Canyon may be 10 million years older than we thought. National parks and monuments Until recently, the Grand Canyon, one of the most spectacular and mysterious natural wonders of the world, was thought to be about six million years old. With improved dating techniques, geologists now believe that it actually started to form some 17 million years ago. Geologists estimated the Grand Canyon's age at six million years by using a technique called uranium-lead dating. The Grand Canyon walls are lined with a sedimentary rockcalled Redwall Limestone. Redwall Limestone can be seen where water levels have dropped, leaving behind deposits of calcium carbonate. Their results showed that six million years ago, a river started from the west and another from the east, carving a mile-deep canyon until they met in the middle and formed what is now the Grand Canyon and the Colorado River. Dating the Grand Canyon Uranium-lead dating allows researchers to determine the age of mineraldeposits hundreds of millions of years old. Over time uranium, which can be found in many mineral deposits, decays into lead. Uranium has a half life of 4.5 million years, which means that only half the original amount of uranium in a rock is left after 4.5 million years. Geologists can collect mineral deposits and find their age by measuring the amount of lead found in the rocks. The amount of lead tells how long the uranium has been decaying. The mineral deposits collected from the Grand Canyon walls reveal when and how fast water levels dropped. New Research In 2008, Victor Polyak led a team of geologists from the University of Mexicoto conduct new research on the Grand Canyon. They also tested minerals that line the canyon walls at different heights in order to track water levels, which allowed them to find the rate at which the canyon deepened. Polyak and his team, however, rafted, hiked, and climbed to access caves that dot the canyon's walls. Many of the caves were difficult to reach—some were hundreds of feet high. In the caves they found mineral deposits that contain larger amounts of uranium. What are mammillaries? The uranium-rich mineral deposits are called mammillaries. Mammillaries are mineral deposits that form at the top of the water table and provide a timeline of the river and canyon’s history. Mammillaries, often called "cave clouds," form just under the surface of water that has a high calcium-carbonate concentration. They leave behind formations, often ring-shaped as seen in trees and stalagmite, on existing rocks. New birth date for the Grand Canyon Polyak and his team collected mammillaries from nine sites in the Grand Canyon that were at a much higher elevation than the current water level and then used uranium-lead dating to find the age of the Grand Canyon. They found that the Grand Canyon eroded much slower on the western end than was previously thought, suggesting it is much older than six million years. Findings also showed that instead of one large river, small streams caused the erosion and they joined to make one large river, the Colorado Riverwhich runs through the Grand Canyon today, stretching 277 river miles long, up to 18 miles wide, and a mile deep. Source: Journal Science 7 March 2008. Web: www.sciencemag.org

Santa Ana Winds: Mysterious autumn winds that warm southern California: In autumn, we often hear about Santa Anawinds exacerbating wild fires in the western states. The fires and their path of destruction are appropriately the focus of the news stories, leaving many to ask, "What are Santa Ana winds?" A meteorological and geographic phenomenon, the Santa Ana winds blow warm air from east to west across southern Californiaeach autumn. They are named after the Santa Ana Canyon in southern California, but are often referred to as "red winds" or "devil winds." Where do they come from? The Santa Ana Winds form in Utah, Nevada, and Arizonabetween the Sierra Nevadaand Rocky Mountains. During the fall, air pressure builds in cold temperatures at high altitudes in this region and forms a drainage wind, which eventually blows down the mountains and out the Great Basintoward the southern California coastline. The winds tend to blow at 35 to 45 mph, but can gust at hurricanespeeds. Why are the winds warm? Although the winds form in cold weather at high altitudes in the mountains, they blow warm, dry air across southern California. As the winds drain out of the mountains, they descend and heat up as the air is compressed in a process called adiabaticheating. The wind also dries on its descent, often leaving its humidity below 10% by the time it reaches the coastline. During the autumn when the Santa Ana winds blow, southern California is at its warmest, often hotter than the deserts. Wildfires When wildfires burn in southern California during the Santa Ana winds, the fires are fueled by the hot, dry winds, causing even greater destruction. In October 2003, 721,791 acres burned in two weeks of wildfires in southern California, fanned by the Santa Ana winds. During wildfires in October 2007, the Santa Ana winds also contributed to the burning of 426,000 acres. Some areas saw wind gusts of 40 to 60 mph, which is equivalent to tropical storm speeds. Other areas had winds traveling at category two hurricane speeds of over 100 mph. In October 2007, wind gusts were recorded at record speeds of 111 mph and temperatures reached 90 degrees with relative humidity below 10%, increasing the intensity of the fires. Although the Santa Ana winds can cause damage, they benefit the environment in other ways. The winds cause cold water to rise to the surface of the ocean, which brings nutrients to the surface. The Santa Anas also make the air in southern California more pleasant by blowing air pollution out to sea. Santa Ana Fog When the Santa Ana winds begin to recede, a fog settles over southern California in its wake. Where dry air prevailed in the lower atmosphere during the Santa Ana winds, a cool moist layer forms quickly after the winds stop, creating a dense fog.

The World's Top Tourism Destinations (international tourist arrivals): The following table shows the top ten tourism destinations according to the number and percent of tourist arrivals in each country during 2010. 2010 rankCountryArrivals (millions)Percent change 2009/2008Percent change 2010/2009 20092010 1.France76.876.8-3.0%0.0 2.United States55.059.7-5.18.7 3.China50.955.7-4.19.4 4.Spain52.252.7-8.81.0 5.Italy43.243.61.20.9 6.United Kingdom28.228.1-6.4-0.2 7.Turkey25.527.02.05.9 8.Germany24.226.9-2.710.9 9.Malaysia23.624.67.23.9 10.Mexico21.522.4-5.24.4 Source:World Tourism Organization (WTO). Web: www.world- tourism.org.