Haystack Rock the U.S. The tallest and probably best known Haystack Rock due to its proximity to Portland is in Tillamook County located off Pacific City and near Cape Kiwanda. It stands above the sea and is the fourth tallest sea stack or off-shore monolith in the world. Haystack Rock in Cannon Beach is accompanied by several smaller rocks known as The Needles. The other Oregon coastal Haystack Rock stands above sea level in Coos County near Bandon. Composed of basalt, Haystack Rock was formed by lava flows emanating from the Blue Mountains and Columbia basin about 15-16 million years ago. The
Lava buried by the advancing flow. This produces a layer of lava fragments both at the bottom and top of an aā flow. Accretionary lava balls as large as are common on aā flows. Aā is usually of higher viscosity than pāhoehoe. Pāhoehoe can turn into aā if it becomes turbulent from meeting impediments or steep slopes. The sharp, angled texture makes aā a strong radar reflector, and can easily be seen from an orbiting satellite (bright on Magellan pictures). Aā lavas typically erupt at temperatures of . The word is also spelled "aa", "aa", "aa", and "a-aa", and pronounced .