Scientists are using this radar image of the area surrounding Sunbury,

Pennsylvania to study the geologic structure and land use patterns in the

Appalachian Valley and Ridge province. This image was collected on October

6, 1994 by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar

(SIR-C/X-SAR) on orbit 102 of the space shuttle Endeavour. The image is

centered on latitude 40.85 degrees North latitude and 76.79 degrees West

longitude. The area shown is approximately 30.5 km by 38 km.(19 miles by 24

miles). North is towards the upper right of the image. The Valley and Ridge

province occurs in the north-central Appalachians, primarily in

Pennsylvania, Maryland, and Virginia. It is an area of adjacent valleys and

ridges that formed when the Appalachian mountain were created some 370 to

390 million years ago. During the continental collision that formed the

Appalachians, the rocks in this area were pushed from the side and buckled

much like a rug when pushed from one end. Subsequent erosion has produced

the landscape we see in this image. The more resistant rocks, such as

sandstone, form the tops of the ridges which appear as forested greenish

areas on this image. The less resistant rocks, such as limestone, form the

lower valleys which are cleared land and farm fields and are purple in this

image. Smaller rivers and streams in the area flow along the valleys and in

places cut across the ridges in "WATER GAPS". In addition to defining the

geography of this region, the Valley and Ridge province also provides this

area with natural resources. The valleys provide fertile farmland and the

folded mountains form natural traps for oil and gas accumulation; coal

deposits are also found in the mountains. The colors in the image are

assigned to different frequencies and polarizations of the SIR-C radar as

follows: red is L-band horizontally transmitted, horizontally received;

green is L-band horizontally transmitted, vertically received; blue is

C-band horizontally transmitted, horizontally received. The river junction

near the top of the image is where the West Branch River flows into the

Susquehanna River, which then flows to the south-southwest past the state

capitol of Harrisburg, 70 km (43 miles) to the south and not visible in this

image. The town of Sunbury is shown along the Susquehanna on the east just

to the southeast of the junction with West Branch. Three structures that

cross the Susquehanna; the northern and southern of these structures are

bridges and middle structure is the Shamokin Dam which confines the

Susquehanna just south of the junction with West Branch. The prominent

S-shaped mountain ridge in the center of the image is, from north to south,

Little Mountain (the top of the S), Line Mountain (the middle of the S), and

Mahantango Mountain (the bottom of the S).

P-45541 April 27, 1995

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Updated 04/28/95

bruce.chapman@jpl.nasa.gov