NASA's Earth Observatory

For those who haven't yet discovered it, may I recommend spending some time browsing through the Web site of NASA's Earth Observatory?

It offers a fascinating look from space at this earth of ours, including an Image Of The Day that can sometimes be quirky, sometimes, scientific, and sometimes spectacularly beautiful. They've got archives running back for years, and I've spent many a break flipping through a few screensful to see if anything takes my fancy.

As an example, here are three images from their archives. I've included the descriptions beneath each picture. Click the images for a larger view.

When Mount St. Helens erupted on May 18, 1980, the north face of the mountain collapsed, and a massive avalanche of rock, mud, and volcanic debris thundered down the mountain. The description of the event on the Mount St. Helens National Monument Website reads, “Nearly 230 square miles of forest [were] blown down or buried beneath volcanic deposits. At the same time, a mushroom-shaped column of ash rose thousands of feet skyward and drifted downwind, turning day into night.”

The creation of a national monument at the site has given scientists the chance to document and study how forests generate from such a major disturbance. Astronaut photographs, such as this one taken on October 28, 2008, collected over nearly three decades have helped to tell the story of the eruption and its long-term effects. Taken from an oblique (side angle) perspective, this photo has a striking three-dimensional quality. The astronaut was photographing the mountain from a vantage point in the east (i.e., looking west.) Mount St. Helens is at image left, and the blast/debris zone is to the right.

Nearly three decades after the eruption, the impact on the forest in the blast zone is still obvious. South of the mountain, lush green forests cover the landscape, while north of the mountain, vegetation remains sparse, particularly on higher elevations. (Some sparsely vegetated areas may be above treeline.) Different areas of the blown down or buried forests are recovering at different speeds. Recovery is slower in forests that had been clear cut before the eruption, and faster in places where vegetation was protected from erosion, wind, drying, and temperature extremes by fallen giants—old growth Douglas fir trees blown down in the eruption—or by snow pack.

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 large coastal desert is one of the oldest in the world, and is caused by a cool ocean current, called the Benguela Current, snaking its way up from the south along southern Africa’s Atlantic Coast. The cold current suppresses rainfall, but contributes to a morning fog that becomes trapped on the surface of some dunes and provides enough moisture for sparse vegetation to grow in some places.

The dunes, pushed up by strong onshore winds, are the highest sand dunes in the world—as high as 300 to 350 meters (1000 to 1167 feet) in places. Rows of linear sand dunes can be seen as alternating ripples of darker and lighter orange in the center of the image. 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.

Cape Town and the Cape of Good Hope, South Africa, appear in the foreground of this perspective view generated from a Landsat satellite image and elevation data from the Shuttle Radar Topography Mission (SRTM). The city center is located at Table Bay (at the lower left), adjacent to Table Mountain, a 1,086-meter (3,563-foot) tall sandstone and granite natural landmark.

Cape Town enjoys a Mediterranean climate but must deal with the limited water supply characteristic of that climate. Until the 1890s, the city relied upon streams and springs along the base of Table Mountain, then built a small reservoir atop Table Mountain to capture and store rainfall there. Now the needs of a much larger population are met in part by much larger reservoirs such as seen here far inland (mid-distance left) at the Theewaterskloof Dam.

False Bay is the large bay to the south (right) of Cape Town, just around the Cape of Good Hope. It is one of the largest bays along the entire South African coast, but nearby Cape Town has its harbor at Table Bay. False Bay got its name because mariners approaching Cape Town from the east would see the prominent bay and falsely assume it to be the entrance to Cape Town harbor. Similarly, people often mistake the Cape of Good Hope as the southernmost point of Africa. But the southernmost point is actually Cape Agulhas, located just to the southeast (upper right) of this scene.

That last picture is particularly meaningful to me, because I was born and raised in Cape Town. I can still vividly remember walking in the mountains with my family, climbing to old reservoirs filled with deep brown, icy-cold water, and drinking from one of the many streams whenever I got too hot or thirsty. The mountain water had a taste all its own. The picture of the Namibian coast, too, brings back many memories. I've written before about the Skeleton Coast. It's a beautiful, haunting, mysterious place.

Anyway, enough of my memories. I encourage you to visit the Earth Observatory and spend time looking at their pictures. There's a Search function, too, so if you want to find pictures of places that are important to you, give it a go. You never know what you may find there!

Peter