Welcome to Earthshots! 

Landsat 8 normally images all Earth landmasses every 16 days. However, at high latitudes, there is considerable overlap because Landsat 8’s orbital tracks converge at the Poles. As a result, this increases the temporal frequency of Landsat 8 coverage over northern Greenland.

Building on this imaging overlap, Landsat 8 takes advantage of long hours of daylight in the Arctic to acquire “nighttime” sunlit images, increasing temporal coverage even more. The two Landsat 8 images were acquired a little over 3 hours apart, one on its descending orbit and one ascending. Having multiple images increases the chances of acquiring more cloud-free images and helps scientists monitor iceberg calving events.

Scientists observed rifts in Petermann Glacier throughout the first decade of the 2000s. The rift that caused the 2010 break was first spotted in satellite imagery in 2001. See below for the location of this rift in a 2001 Landsat image.

The massive calving event in 2010 removed 28 kilometers of the ice shelf. The result was an ice island four times the size of Manhattan, about 270 square kilometers. It was the largest iceberg to form in the Arctic since 1962.

The last image displayed in this section shows a size comparison of Manhattan Island (yellow outline) to the iceberg.

(Black stripes run through the images because of the Scan Line Corrector failure on Landsat 7 in May 2003.)

Just two years later, another large iceberg broke off Petermann Glacier. This one was estimated at 130 square kilometers—about half the size of the 2010 iceberg. But this calving broke off the glacier tongue farther upstream and moved the front end of the glacier farther inland than has been observed since 1876, the first reported measurements of the glacier.

The floating ends of glaciers like Petermann are known as ice shelves. They act as doorstops. When these ice shelves suddenly splinter and weaken, the glaciers that feed them speed up. The result is more ice flowing into the ocean, which could raise global sea levels.

The development of these icebergs is a natural process; however, when there are two major breaks in two years, scientists must take notice. Even large breaks do not amount to a collapse of the floating extension; nevertheless, they are important events.

(Black stripes run through the images because of the Scan Line Corrector failure on Landsat 7 in May 2003.)

A new rift formed on Petermann Glacier in 2017. An older crack to the right of the new rift also extends toward the glacier’s center. By 2020, this new rift had met up with the older crack. If an iceberg breaks off, it would be Petermann’s third massive iceberg calving since 2010. It also could place the new calving face much farther upstream than the 2010 break.

Close-up images from Sentinel-2 take advantage of its 10-meter spatial resolution to show the new rift in greater detail. Landsat 8 and Sentinel-2 complement each other by imaging glacial movement and possible calving events.

The prominent vertical line could be from deformation of the ice as it flows over the bedrock farther upstream. The irregular topographic surface of the underlying bedrock could have caused the ice to develop this longitudinal crevasse as it moved over bedrock, resulting in a line being drawn the length of the glacier as it flows. Besides the new rift, other bumps and lines extend from this longitudinal line, which are stress fractures from the glacial movement.

Along with becoming longer, notice that the rifts are also moving downstream between 2017 and 2022 as the glacier flows.

On April 30, 2018, rapid changes in the East Rift Zone were detected. The Pu‘u ‘Ō‘ō crater floor collapsed. Ground deformation toward the east indicated magma intrusion approaching the Leilani Estates neighborhood, 20 km from Pu‘u ‘Ō‘ō.

Based on numerous geological, geochemical, and geophysical instruments, the USGS Hawaiian Volcano Observatory and other scientists determined that magma had drained from below Pu‘u ‘Ō‘ō crater. It then intruded through underground tunnels and emerged at eruptive vents, or fissures, in the lower East Rift Zone.

On May 3, the first of 24 fissures along a 6-km line opened within Leilani Estates. Fissure 8 became the dominant vent on May 28. It shot lava tens of meters into the air and sent a vigorous flow toward the coast, ultimately entering the ocean near the eastern tip of the island.

This series of images shows the progression of the lava flows throughout the summer of 2018. Clouds often obscure views of the island, but numerous observations from Landsat, Sentinel-2, and Resourcesat offered peeks through the clouds to the location of fresh lava. Some of the images also show “laze.” When lava mixes with seawater, it creates a noxious gas plume that looks like clouds or smoke. The word is a blend of the words lava and haze. Laze can cause skin and eye irritation and breathing difficulties.

This flow ended abruptly on August 4, 2018. By this time, lava had destroyed more than 700 structures, covered 13.7 square miles (35.5 km²) of land, and added about 741 acres (300 hectares) of land to the island. Lava was a couple hundred meters thick in some places.

A wet 2018–2019 winter caused extra plant growth on Maui, and thus extra fuel, and was followed by drought and record-breaking heat in summer 2019. That set up conditions for an intense fire season. Firefighters reported the unusual weather conditions that made the fires worse: above normal temperatures and below normal humidity.

In summer 2019, at least 19,300 acres burned across Maui, nearly all of it in the former cane fields. The dry grasses that largely replaced the cane fields are especially vulnerable to fire. Notice that the fire scar visible in the July 27, 2019, image didn’t last long, evidence that, unlike a forest fire burn scar, nonnative grass recovers rapidly and outcompetes native grasses after a fire.

Taking a closer look at Garden City shows the expansion in area the city experienced since 1972. They also show the proximity of the city to those center-pivot irrigation circles. Four of these circles take up almost 1 square mile, or one section, of land.

Southwest of Garden City is an area absent of irrigated crops. This marks the location of the Sandsage Bison Range Wildlife Area, a reserve for many Plains natives, including an American bison herd.

Another gap in irrigated cropland is a bit to the west of the game refuge. Marked by light spots is Holcomb Station, a coal-fired power plant operated by the Sunflower Electric Power Corporation. The plant opened in 1983, so it does not appear in the 1972 Landsat image. The 362-megawatt station uses coal mined in Wyoming's Powder River Basin.

The coastal wetlands of Senegal are centered on the Saloum River and a myriad of estuaries and tidal flats that make up this complex ecosystem. The estuaries are generally bordered by dense, vigorous stands of mangroves (dark red tones in the Landsat images). Part of this ecosystem is protected in Saloum Delta National Park. The wetlands are critical habitats for wintering Palearctic birds, as well as many species of fish and mollusks.

The mangrove vegetation is made up of several species. Some mangrove species form low canopies, but others of the Rhizophora genus are among the tallest in the world, attaining heights of up to 40 meters. Mangroves grow in habitats that are periodically flooded by seawater (tidal influence) and river water. They are halophytes, plants that grow in salty environments.

Since the late 1960s, it has become apparent that many of the mangrove forests are dying. One theory is that there is a serious mangrove disease that is systematically wiping