Owens Valley, shown in this space shuttle view, is a large extensional fault-bounded trough on the eastern side of the Sierra Nevada Mountains. This 3000-meter-deep valley is the westernmost part of the Basin and Range structural province, which covers large parts of Nevada and Utah. The Basin and Range formed when the crust in the western United States was stretched in an east-west direction, producing a series of north-south-trending extensional faults. This faulting produced a classic horst and graben topography consisting of a series of alternating valleys and mountain ranges.
The snow-capped Sierra Nevada Mountains at bottom consist of numerous overlapping granitic batholiths. They represent the deeply eroded core of a continental volcanic arc that was active in the late Mesozoic era, and probably resembled the Indonesian or Andean continental volcanic arcs of today. Most of the surface volcanic materials have since been eroded away. Glaciation in recent times has produced a variety of glacial valleys and landforms throughout the Sierras. A major eruption about 730,000 years ago formed the Long Valley caldera, the 17 × 32-kilometer-wide circular depression at center left centered near the dark hook-shaped lake. Volcanic activity in this area began around 3.2 million years ago, with the most recent eruption occurring in the past 500 years.
STS 41G Large
Format Camera images 41G-2059, 41G-2060.