Unlike rural communities, urban sprawl completely transforms the landscape and the soil and alters the surrounding ecosystem and the climate.

"Earthrise" over the lunar horizon was taken by the Apollo 8 crew in December 1968, showing Earth for the first time as it appears from deep space. Astronauts Frank Borman, Jim Lovell and William Anders had become the first humans to leave Earth orbit, entering lunar orbit on Christmas Eve.

Welcome to Planet Earth, the third planet from a star named the Sun. The Earth is shaped like a sphere and composed mostly of rock. Over 70 percent of the Earth's surface is water. The planet has a relatively thin atmosphere composed mostly of nitrogen and oxygen.

Taking advantage of remarkably fair weather over north central Europe for the time of year, the crew of the International Space Station took this panoramic view that extends from the North Sea coast of the Netherlands on the left to the Baltic Sea shores of Sweden on the right. The late-winter landscape has little snow cover except over northeastern Germany, Sweden, and the rugged mountains of Norway.

Behind Santa Ana is a large caldera lake inside the Coatepeque Caldera, created when a series of volcanoes collapsed in explosive eruptions between 57,000 and 72,000 years ago. In the foreground is El Salvador’s newest volcano, Izalco, which sprang up in 1770 and erupted frequently until 1966. The young volcano isn’t covered in vegetation (red in this image), but remains black with recent lava flows.

Astronauts on board the International Space Station recently took advantage of their unique vantage point to photograph the Himalayas, looking south from over the Tibetan Plateau. The perspective is illustrated by the summits of Makalu [left (8,462 meters; 27,765 feet)] and Everest [right (8,850 meters; 29,035 feet)] -- at the heights typically flown by commercial aircraft.

A fortuitous orbit of the International Space Station allowed the astronauts this striking view of Sarychev volcano (Russia’s Kuril Islands, northeast of Japan) in an early stage of eruption on June 12, 2009. The smooth white cloud on top may be water condensation that resulted from rapid rising and cooling of the air mass above the ash column, and is probably a transient feature (the eruption plume is starting to punch through).

Warm ocean waters fuel hurricanes, and there was plenty of warm water for Katrina to build up strength once she crossed over Florida and moved into the Gulf of Mexico. Every area in yellow, orange or red represents 82 degrees Fahrenheit or above. A hurricane needs SSTs at 82 degrees or warmer to strengthen.

Snow highlights the peaks of the Banks Peninsula to the southeast of the city. Other interesting features in the image include the braided Waimakariri River to the north-northwest of the city, and the greenish brown waters of Lake Ellesmere at image left. The coloration of the water is due both to its shallow depth (1.4 meters on average, or about 4.5 feet) and its high concentrations of nitrogen and phosphorus, which fertilizes the growth of large amounts of green algae.

At 86 meters (282 feet) below sea level, Death Valley is one of the hottest, driest places on the planet. The dots of brilliant green near the right edge of the image fall outside park boundaries, and probably result from irrigation. The varying shades of brown, beige and rust indicate bare ground; the different colors result from varying mineral compositions in the rocks and dirt. Although they appear to be pools of water, the bright blue-green patches in the scene are actually salt pans that hold only a little moisture.

Over 120 million years ago, a single mass of granite punched through the Earth’s crust and intruded into the heart of the Namib Desert in what is now northern Namibia. To the southwest of Brandberg Massif, an older and more-eroded granite intrusion blends in subtly with the desert landscape, while along the Ugab River at upper left, cracks line the brown face of an ancient plain of rock transformed into gneiss by heat, pressure, and time.

The tongue of the Malaspina Glacier, the largest glacier in Alaska, fills most of this image. The Malaspina lies west of Yakutat Bay and covers 1,500 square miles (3,880 square kilometers).

On the southwest coast of Africa, the soft orange sands of Namibia's coastal desert rise to a rugged interior plateau, with outcroppings of colorful rocks and pale green vegetation. The dunes, pushed up by strong onshore winds, are the highest sand dunes in the world --as high as 1,000 to 1,167 feet in places. The dune shapes become more chaotic surrounding the mud plain where a river runs down out of the plateau (left of center), but doesn’t make it to the ocean.

Mount Saint Helens exemplifies how Earth's topographic form can change greatly even within our lifetimes. Prior to 1980, Mount Saint Helens had a shape roughly similar to other Cascade peaks, a tall, bold, irregular conic form that rose to 9,677 feet (2,950 meters). However, the explosive eruption of May 18, 1980, caused the upper 1,300 feet (400 meters) of the mountain to collapse, slide and spread northward, covering much of the adjacent terrain.