Observing Earth

Observing Earth

Geologists have always sought the high groung to assess the lay of the land, and aerial photography gave scientists a welcome vantage point. Artificial satellites took that concept to new heights, providing reconnaissance to the military(The U.S Corona series was the first, about 1960), and then giving science a global perspective with Landsat and others. On California's northwest coast lies San Francisco Bay, bisected By the San Andreas Fault, a tectonic fault where the pacific and the North American crustal plates grind past each other. Modern San Francisco stands astride the fault, which in 1906 lurched more than 20 feet, destroying more than 28,000 buildings and killing more than 3,000 people. This large image pictures the financial district, Embarcadero, and Oakland Bay Bridge, seen from IKONOS satellite. To observe this geologically important region, scientists have used not just orbital photography but portions of the electromagnetic spectrum ou eyes can't see. Visible light can show us details of street plans, vegetation patterns, and surface geology. But other wavelengths can reveal the type and health of vegetation, delineate land-use patterns, and trace unstable tectonic underpinnings of this vulnerable region. In the same way, planetary scientists examine a planet's surface using a range of wavelengths, looking for different rock types(lave, crustal bedrock, water-bearing sediments, ice buried under dust) or revealing landforms shrouded by haze or clouds.