Pine Valley Laccolith near St. George, Utah (view from the south)
A laccolith is a underground intrusion of molten lava, frequently, as here, emplaced in a weak zone between the horizontal layers of sedimentary deposits. The laccolith in the center is one of the largest structures of this type, covering an area of 1500 square kilometers (590 square miles), up to 1000m (3000 feet) thick. The overlying sedimentary rock has long disappeared, but the underlying red Claron Formation layers visible in some spots (right Center). The red rocks of Zion National Park are visible in the distance
Pine Valley Laccolith near St. George, Utah (view from the south)
A laccolith is a underground intrusion of molten lava, frequently, as here, emplaced in a weak zone between the horizontal layers of sedimentary deposits. The laccolith in the center is one of the largest structures of this type, covering an area of 1500 square kilometers (590 square miles), up to 1000m (3000 feet) thick. The overlying sedimentary rock has long disappeared, but the underlying red Claron Formation layers visible in some spots (right Center). The red rocks of Zion National Park are visible in the distance