ke with an image from a previous date allows scientists to map the exact locations and extent of local changes caused by the landslides. Here, the post-event (May 8) WorldView-2 image shows one major landslide, as well as many smaller-scale slides that also occurred along the Buri Gandaki river valley after the earthquake. The image also shows a new lake that formed behind the largest landslide, as a result of damming of the Tom Khola River.
This inset image pair shows just one location, and these changes have occurred across the landscape, especially in the mountainous regions.
Scientists will continue to monitor the region with various satellite data. As post-event images become available, earthquake damage and landslide maps are being created and updated. For more information (including earthquake damage assessments and a landslide inventory map) see the International Charter ‘Space and Major Disasters’ home page: https://www.disasterscharter.org.
35th Anniversary of Mount St. Helens Eruption May 20, 2015
The violent eruption of Mount St. Helens 35 years ago permanently changed the mountain and surrounding forest. The volcanic blast on May 18, 1980, devastated more than 150 square miles of forest within a few minutes. In these Landsat false-color images, forest appears as bright red interspersed with patches of logging. Snow appears white, and ash is gray.
Before the eruption, Mount St. Helens towered about a mile above its base, but when the volcano erupted, its top slid away in an avalanche of rock and debris. When measured on July 1, 1980, the mountain’s height had been reduced from 9,677 feet to 8,364 feet—a difference of about 1,300 feet.
The 2014 Landsat image shows vegetation regrowth, as light red and pink, in the devastated area. However, the gray around the mountain is still evident, and the volcanic crater is still prominent as an “amphitheater,” where the peak of the mountain slid away.
Scientists are using this opportunity to witness the recovery process, both with satellites and on the ground. With its 40-plus years of consistent imagery, the Landsat archive is perfect for studying the landscape changes caused by natural disasters and the gradual recovery process.
Haruj is the large volcanic field that dominates this Landsat image mosaic acquired over central Libya. The plateau was built from basaltic lava flows that erupted over time from approximately 150 separate volcanoes. The volcanic craters and lava flows are all evidence of a previous active period, well preserved in the dry Sahara Desert.
The geologic evolution of this landscape is not fully understood, but some scientists have used the texture and color differences revealed in satellite images to try to interpret the relative ages and sequence of different volcanic events. The numerous spectral bands and band combinations available from Landsat mean that the color variation of individual lava flows can be especially helpful for interpreting different phases of volcanic activity.
Many of the bright spots within the darker colored basalt flows are sand-filled craters associated with individual volcanoes. Other light-colored areas are depressions covered with silt and fine sand.
This image mosaic consists of numerous Landsat 8 scenes acquired in early 2015. Landsat images can be useful to support geologic mapping and studies of large and remote features such as this.
Lake Urmia, located in northwestern Iran, was once one of the largest saltwater lakes in the Middle East. It supports an important seasonal habitat for many species of migrating birds.
In recent years, the lake has diminished dramatically. Water enters Lake Urmia primarily from rainfall and inflowing rivers. The diversion of water from local rivers for agricultural use is one likely cause of Lake Urmia’s decline. Since 1996, drought has further contributed to the lower lake levels. The lake now covers about 10 percent of the area it covered in the 1970s.
These Landsat images show the changes to Lake Urmia’s surface area over the past fourteen years. Each image was created by mosaickin