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Mount Cleveland Volcano and Islands of the Four Mountains, Alaska, USA – October 31st, 2011

52.8N 169.9W

October 31st, 2011 Category: Image of the day, Volcanoes

USA - October 29th, 2011

This orthorectified image shows the Islands of Four Mountains, an island grouping of the Aleutian Islands in Alaska, United States. The chain includes, from west to east, Amukta, Chagulak, Yunaska, Herbert, Carlisle, Chuginadak, Uliaga, and Kagamil Islands.

This island chain is located between Amukta Pass and the Andreanof Islands to the west, and Samalga Pass and the Fox Islands to the east. These islands have a total land area of 210.656 sq mi (545.596 km²) and have no permanent population.

The two largest islands are Yunaska and Chuginadak. Chuginadak is mainly made up of the active volcano Mount Cleveland, a nearly symmetrical stratovolcano on the western end the island. Mount Cleveland is 1730 m high, and one of the most active of the 75 or more volcanoes in the larger Aleutian Arc. Mount Cleveland erupted three times in 2009, twice in 2010, and once in 2011.

Volcanoes of Unimak Island, Alaska, USA

November 1st, 2010 Category: Mountains, Volcanoes

USA - September 12th, 2010

This orthorectified image focuses on Unimak Island, one of the Aleutian Islands in Alaska. Numerous volcanic features can be observed on the island.

Situated at the left edge are the Pogromni Volcano and the Mount Westdahl stratovolcano. Pogromni is old and eroded, and historic eruptions attributed to it may have come from nearby Westdahl volcano.

Moving eastward across a low crater, one comes to the peak of Mount Shishaldin, a moderately active volcano. It is the tallest volcano in the Aleutian Islands. The most symmetrical cone-shaped glacier-clad large mountain on earth, the volcano’s topographic contour lines are nearly perfect circles above 6,500 feet.

Continuing eastward, one finds the Isanotski Peaks or Isanotski Volcano, a multipeaked mountain. It is an old, highly dissected stratovolcano, lying about 10 miles (16 km) east of Shishaldin Volcano, the highest peak in the Aleutian Islands. Its height is also often given as 8,025 feet (2446 m). In contrast to many of the younger, symmetrical volcanoes of the region, Isanotski is topped by multiple rugged pinnacles.

Vegetation Index of Alaska, USA

62.1N 158.6W

October 4th, 2010 Category: Vegetation Index

USA - August 23rd, 2010

This FAPAR image shows the vegetation index of much of Alaska, the largest state of the United States by area. Marshlands and wetland permafrost cover 188,320 square miles (487,747 km2) (mostly in northern, western and southwest flatlands).

Here, the state’s vegetation index appears generally good (green), with some areas of lower photosynthetic activity (yellow) mostly in the upper right quadrant. Upon opening the full image, smaller patches of high activity (rusty red) can be observed on the islands of the Aleutian Chain, to the south.

Mount Okmok and Okmok Caldera, in Alaska, USA

53.4N 168.1W

February 14th, 2010 Category: Mountains, Volcanoes

USA - February 4th, 2010

USA - February 4th, 2010

This orthorectified image shows the wide, circular Okmok Caldera, which truncates the top of a large shield volcano. The highest point on the caldera rim is  called Mount Okmok. Both are located in the northeastern part of Umnak Island in the eastern Aleutian Islands of Alaska, USA.

Although the last major eruptions of Okmok—with an estimated VEI strength of 6—occurred 8,300 and 2,400 years ago, on Saturday, July 12, 2008, Okmok Caldera exploded without warning, sending a plume of ash over 33,000 feet (10,000 m) into the air. No lava flow was reported, though the volcano has issued flows in the past.

Before then, the volcano had last erupteded in 1997 and produced a lava flow, once again erupting with no initial warnings. Residents of Fort Glenn, a nearby ranch, fled from falling ash and volcanic rock.

Shield and Strato-Volcanoes of Umnak Island, USA

53.1N 168.5W

December 9th, 2009 Category: Volcanoes

Alaska, USA - November 10th, 2009

Alaska, USA - November 10th, 2009

Volcanoes with distinctive shapes can be observed on Umnak Island, one of the Aleutian Islands that are part of the state of Alaska, USA, in this orthorectified image. The northern end of the island is mostly occupied by the circular volcanic caldera of Mount Okmok.

The southern end of the island is home to the steep symmetrical cone of Mount Vsevidof  and the heavily eroded Mount Recheshnoi (right of the former).

Both Mount Vsevidof and Mount Recheshnoi are stratovolcanoes, while Mount Okmok is a shield volcano. The summit of Mount Vsevidof is the highest point on Umnak Island at 7051 ft (2149 m), while its neighbor Mount Recheshnoi is lower, due in part to erosion, with a maximum elevation of 6,509 feet (1984 m). Returning to the north end of the island, Mount Okmok itself, near the caldera rim, is much lower than its southern-end counterparts, with a height of 3,520 feet (1073 m).

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