Description: Aerial view, looking east, of Aniakchak caldera, one of the most spectacular volcanoes on the Alaska Peninsula. Formed during a catastrophic ash-flow producing eruption about 3,400 years ago, Aniakchak caldera is about 10 km (6 mi) across and averages 500 m (1,640 ft) in depth. Voluminous postcaldera eruptive activity has produced a wide variety of volcanic landforms and deposits within the caldera. The volcano is located in Aniakchak National Monument and Preserve, Alaska, which is administered by the National Park Service.

Image by M. Williams, National Park Service – Public domain – Wikimedia

Description: Aerial view over a valley containing a river and lake with mountains in the distance December 1, 1978 and December 2, 1980: The Aniakchak Caldera, covering some 30 square miles, is one of the great dry calderas in the world. Located in the volcanically active Aleutian Mountains, the Aniakchak last erupted in 1931. The crater, lava flows, cinder cones, explosive pits, and Surprise Lake are vibrant reminders of Alaska's location in the volcanically active "Ring of Fire”.

Image by NPS – Public domain – Wikimedia

Description: View of the caldera and Surprise Lake The Aniakchak Caldera, is the result of a series of eruptions, the latest in 1931. Nearly six miles in diameter and covering some ten square miles, it is one of the finest examples of dry caldera in the world. Located in the volcanically active Aleutian Mountains, the crater contains many outstanding examples of volcanic features, including lava flows, cinder cones, and explosion pits. Surprise Lake, located within the caldera, is the source of the Aniakchak River, which cascades through a 1,500-foot gash in the caldera wall. The site also contains the Aniakchak Wild River. Keywords: ania; caldera; National monuments; Conservation of natural resources; Volcanos; Natural preserves

Image by NPS staff – Public domain – Wikimedia

Description: Another view of caldera and lake. The Aniakchak Caldera, is the result of a series of eruptions, the latest in 1931. Nearly six miles in diameter and covering some ten square miles, it is one of the finest examples of dry caldera in the world. Located in the volcanically active Aleutian Mountains, the crater contains many outstanding examples of volcanic features, including lava flows, cinder cones, and explosion pits. Surprise Lake, located within the caldera, is the source of the Aniakchak River, which cascades through a 1,500-foot gash in the caldera wall. The site also contains the Aniakchak Wild River. Keywords: ania; caldera; National monuments; Conservation of natural resources; Volcanos; Natural preserves

Image by NPS staff – Public domain – Wikimedia

Description: Natural-colour image of Aniakchak National Monument and Preserve. A caldera dominates the view, and the southern rim casts a blue-gray shadow on nearby snow and ice on the slopes. (Because of the angle of sunlight, this image may cause the optical illusion known as relief inversion.) A lake lies near the caldera’s northeastern margin. Vegetation is scarce immediately around the caldera, but slopes are green farther away.Image captured by the Enhanced Thematic Mapper Plus on the Landsat 7 satellite. Landsat data provided by the United States Geological Survey.

Image by Jesse Allen and Robert Simmon – Public domain – Wikimedia

Description: Location Aniakchak National Monument and Preserve Description Given its remote location and notoriously bad weather, Aniakchak is one of the least visited units of the National Park System. A vibrant reminder of Alaska's location in the volcanically active "Ring of Fire," the monument is home to an impressive six-mile wide, 2,500 ft. deep caldera formed during a massive eruption 3,500 years ago

Image by National Park Service Digital Image Archives – Public domain – Wikimedia

Description: Location Aniakchak National Monument and Preserve Description Given its remote location and notoriously bad weather, Aniakchak is one of the least visited units of the National Park System. A vibrant reminder of Alaska's location in the volcanically active "Ring of Fire," the monument is home to an impressive six-mile wide, 2,500 ft. deep caldera formed during a massive eruption 3,500 years ago

Image by National Park Service Digital Image Archives – Public domain – Wikimedia

Description: Caldera of Aniakchak Volcano, Aniakchak National Monument and Preserve, Alaska, USA. View from NE rim across Surprise Lake to Half Cone.

Image by Game McGimsey, Alaska Volcano Observatory / U.S. Geological Survey – Public domain – Wikimedia

Description: Least Sandpiper in Kujulik Bay, Aniakchak national Monument and Preserve, Alaska Photo credit: Bill Thompson/NPS

Image by National Park Service, Alaska Region – Public domain – Wikimedia

Description: NASA image acquired September 15, 2000 To download the full high res go to: earthobservatory.nasa.gov/IOTD/view.php?id=73854&src=... Aniakchak National Monument and Preserve derives its name from a 6-mile (10-kilometer) wide caldera that sits midway down the Alaskan Peninsula. Geographers first noticed the circular feature on the landscape, and a 1922 geologic expedition confirmed the origin of the depression. Several decades later, paleontologists made another find at Aniakchak: Dinosaurs once lived in the area, and they left behind some of their fossilized tracks. Aniakchak is one of 232 American parks with a stash of fossils. The National Park Service provides information on these natural relics as part of its celebration of National Fossil Day (October 12) and of Earth Science Week. The Enhanced Thematic Mapper Plus on the Landsat 7 satellite captured this natural-color image of Aniakchak National Monument and Preserve on September 15, 2000. The caldera dominates the view, and the southern rim casts a blue-gray shadow on nearby snow and ice. (Because of the angle of sunlight, this image may cause the optical illusion known as relief inversion.) A lake lies near the caldera’s northeastern margin. Vegetation is scarce immediately around the caldera, but farther away the slopes are green. The caldera formed about 3,500 years ago when an explosive eruption blew out roughly 3,000 feet (1,000 meters) of overlying mountain. More recent volcanic activity has pockmarked the caldera with cinder cones and lava flows. The dinosaur tracks in Aniakchak are far older than the crater. They were left by plant-eating dinosaurs about 70 million years ago. Anthony Fiorillo, based at the Museum of Nature and Science in Dallas, discovered the tracks and wrote about them in 2004. Left by hadrosaurs, the tracks consist of smaller handprints and larger footprints. Most people think dinosaurs lived in tropical, or at least temperate, environments—not at high latitudes such as Alaska. So how could dinosaurs thrive so far north? Plate tectonic theory indicates that some lands that are now situated at high latitudes once rested nearer to the equator. So one explanation could be that the landform wasn’t in the same place when the tracks were formed. However, studies of rock layers from the area indicate that the Aniakchak area was already in place at about the same latitude 70 million years ago. Though Aniakchak was in roughly the same place (almost 57 degrees north), it doesn’t mean that it had the same climate. In fact, global climate about 70 million years ago was significantly warmer than today. So dinosaurs did not have to endure the temperatures common in modern Alaska, although they did experience some cold conditions and possibly snow. NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using Landsat data provided by the United States Geological Survey. Caption by Michon Scott. The Earth Observatory’s mission is to share with the public the images, stories, and discoveries about climate and the environment that emerge from NASA research, including its satellite missions, in-the-field research, and climate models.

Image by NASA's Earth Observatory – CC BY 2.0 – Wikimedia