City geography Island Park is located at an
elevation of
above sea level, making it the highest city in Idaho. According to the
United States Census Bureau, the city has a total area of , of which, is land and is water.
Regional geography The area was known as Island Park long before the -long town was incorporated. The area known as Island Park is mostly a large crater or
caldera named the
Henry's Fork Caldera that was created by the same
hotspot that created the earlier
Island Park Caldera and the later
Yellowstone Caldera. drainage In addition to the portion which lies on the Henry's Fork Caldera, about a third of what is known as Island Park is north of the caldera, extending across Henry's Lake Flat and Henry's Lake towards the Idaho/Montana border. Henry's Lake Flat is a flat bottomed valley between high mountain ranges, with
Henrys Lake at the northwest end of the flats.
Mount Jefferson, south of Henry's Lake, is high and Targhee Peak, north of Henrys Lake is high. The most famous of Island Park's peaks, however, is the
Sawtell Peak, south of Henrys Lake near Mount Jefferson. The peak is known for its beauty and is named for a perceived resemblance to a
Native American chief's profile while napping. The peak has also been called Chief Rains in the Face. Sawtell Peak is topped by a
FAA radar dome and is visible from nearly anywhere in Island Park. Although much smaller than either the Island Park Caldera or the Yellowstone Caldera, the Henry's Fork Caldera is still one of the largest calderas in the world and is the only large caldera in the Yellowstone region that is plainly visible. It has a nearly level wide circular floor that slopes slightly towards the southeast. The caldera floor is at about of
elevation with the rim generally being several hundred feet higher. The Henry's Lake Flat area, north of the caldera, is a little higher. Henry's Lake sits at about , with the flats sloping slightly southward towards the caldera. The Island Park area is mostly forested with many meadows and grasslands. It is mostly level, but is surrounded by forested hills and high mountains in the north. The
Henrys Fork of the Snake River meanders through Island Park with its headwaters at Henry's Lake and at
Big Springs (Idaho). The Henry's Fork is impounded by
Island Park Dam to form Island Park Reservoir outside the north rim of the caldera. In fact, the entire south bank of Island Park Reservoir is formed by the northern slope of the caldera. The Henry's Fork crosses through the caldera and then cascades off from it at
Upper and Lower Mesa Falls. and
Indian Paintbrush in background The geography of Island Park is actually unique and distinctive. It is largely flat and it has unusually high precipitation. Island Park is at the same elevation as Teton Valley, Idaho, Jackson Hole, Wyoming, or the Centennial Valley, Montana; yet while these nearby areas are semi-arid prairie or even desert areas receiving less than of precipitation annually, Island Park is forested and green with many streams, ponds, lakes, and meadows. Island Park receives well over of precipitation annually, with parts receiving over . That is, Island Park has three times the rainfall and snowfall as nearby areas of the same elevation. The
Snake River Plain that was also formed by the Yellowstone
hotspot aligns with the gap between the
Sierra Nevada and
Cascade mountain ranges along the
West Coast of the United States so that there is a
moisture channel that extends from the distant
Pacific Ocean, between the Cascades and Sierra Nevada, through the
Rocky Mountains to Island Park. This abundant precipitation in Island Park falls on the relatively level floor of the caldera, where it forms numerous meandering streams, ponds, marshes, and meadows. It also falls on the higher areas to the east along the Yellowstone Park border, where it percolates though the granular volcanic deposits to emerge as some of the largest springs in the world.
Big Springs, Buffalo River Springs, and Warm River Springs all are
1st Magnitude springs, and they form some of the crystal-clear meandering streams that the area is famous for.
Climate Island Park has a
humid continental climate (Dsb), bordering on a
subarctic climate (Dsc). Summer days are usually warm, with nights dropping to temperatures around 40, while winters are very cold, with massive yearly snowfall averaging . It is the site of Idaho's lowest recorded temperature, , on January 18, 1943. ==Demographics==