Photograph of Sólheimajökull outlet glacier in Iceland. More information can be found on page 118 of this new publication. This includes a more detailed graphic of fluctuations in temperature and how that corresponded to glacier advance/retreat.

Water, the key to life, is also a key to understanding the way the natural world works. Water in the form of ice is especially instructive.

Water moves through the hydrologic cycle, one of the most basic and vital processes of Earth’s systems, in three forms — as a liquid in seas and streams; as a vapor in clouds and fog; and as a solid in ice. Found predominately in glaciers, the world’s ice is, by nature, temperature dependent. Thus the presence or absence of glaciers and their geographic distribution around the globe are closely linked to Earth’s historical and current climate conditions and to changes in global sea level.

The recently published State of the Earth’s Cryosphere at the Beginning of the 21st Century summarizes past and present-day changes in the Earth’s cryosphere (the whole of its frozen water) and describes the ongoing and potential effects of those changes. Extensively illustrated in print and connected to a companion online image gallery, this volume supplies a synthesis for 10 other geographically-based volumes in the 11-volume Satellite Image Atlas of Glaciers of the World.

“Evidence from a wide range of satellite and field observations over the last 30 years shows that nearly all glaciers, snowpack, sea ice, and permafrost are in retreat around the globe,” said USGS Director Marcia McNutt. “That this worldwide phenomenon can be readily observed by a non-specialist without any sophisticated data processing or image enhancement is strong evidence that our rapidly warming planet is causing major changes in one of the key Earth systems.”

Glaciers as Climate Indicators

Glaciers cover about 15.9 million square kilometers of Earth’s land surface (2009 figures), slightly less than the size of Russia. Ice sheets in Antarctica and in Greenland store most of the glacier ice on Earth, occupying 95.5 percent of glacier area and containing 99.4 percent of glacier volume. Other glaciers are located on all of Earth’s continents except Australia. (The term glacier in the Satellite Image Atlas includes ice sheets, a long-held definition also used by the Scott Polar Research Institute and the American Geosciences Institute.)

Glaciers have waxed and waned throughout the history of Earth in response to several factors: the global climate, the latitudinal position of the continents, the geographic position and elevation of mountain ranges, and slight changes in the Earth’s orbit. Presently, glaciers around the world are responding to natural warming after the end of the Little Ice Age in the late 1800s, as well as to the warming that human activity has caused through increased concentrations of carbon dioxide and other greenhouse gases in the atmosphere.

For example, since the late 19th century, all of Iceland’s glaciers have decreased in area and thickness. Although Iceland’s glaciers retreated from 1930 through 1970, they advanced during 1970 to 1995. Since 1995, however, the decrease has been quite dramatic. If the climate continues to warm, glaciers in Iceland will probably decrease by 40 percent during the 21st century and will virtually disappear by 2200.

The overwhelming scientific consensus is that burning of fossil fuels and deforestation, both of which are human activities, are critical factors in the Earth’s observed warming.

Landsat image of the largest ice cap in Europe, the Vatnajökull ice cap. More information and this image can be found on page 91 of the new publication.

Melting Glaciers ­— Rising Seas

Water covers 70 percent of the Earth’s surface. Of all the world’s water, water in the oceans makes up 97 percent while frozen water in glaciers accounts for just 2 percent.

Although 2 percent seems like a small ratio, it is the long-term exchange between glacier ice and the oceans that principally determines global sea level. Warming of the Earth alters the relationship between global sea level and the volume of glacier ice on land, as frozen water is converted to meltwater and transferred from land to the oceans. The warming of the Earth’s oceans also serves to increase the volume of the water and add to global sea rise.

In response to variations in the volume of glacier ice on the continents, sea level has repeatedly fallen and risen between glacial and interglacial periods of Earth’s geologic history. Approximately 20,000 years ago, for example, sea level was about 125 meters (410 feet) lower than at present (2009 figures). If all of the present glacier ice on land were to melt, sea level would rise an additional 75 meters (246 feet).

The present rate of the global rise in sea level is now about 3-4 mm each year, equivalent to a stack of three to four U.S. pennies.

The Cryosphere: Beyond Glaciers

The cryosphere (from Greek, cryos, “cold”) is the term that describes the portions of the Earth’s surface where water is in solid form. It includes glaciers, snow cover, floating ice, and permafrost, although glaciers are the dominant component.

Global snow cover is measured on a daily basis, and snow-cover trends can be measured over decades. These advances have important applications to hydrological forecasting, enabling us to predict flooding and water supply.

Sea ice covers vast areas of the polar oceans, affecting the atmosphere, the oceans, and terrestrial and marine ecosystems of the polar regions. Changes in the ice, if sufficiently large, can initiate regional and global climatological and ecological consequences. This publication notes that 2007 was a record low year for Arctic sea ice extent, but an even lower minimum was recorded more recently in September 2012.

Permafrost or perennially frozen ground includes northern peatlands and frozen, organic-rich sediments that contain large amounts of carbon. Deep, perennially frozen sediments, both onshore and beneath the Arctic shelves, contain methane hydrates. These carbon-rich deposits are potential sources of greenhouse gases, especially methane, if climate warming continues.

The Cryosphere in Education

A substantial section of the new volume is designed for use by teachers and students in the classroom to improve the understanding of major aspects of global environmental change. The print version of this section contains a wall-size plate, “Earth’s Dynamic Cryosphere,” and eight Supplemental Cryosphere Notes (two-page summaries of topics included in the report). These materials support a major national effort to increase higher-education student enrollment in the Earth sciences.

Global Collaboration and Space-Based Views

Image of the Greenland ice sheet. More information and this image can be found on page 89 of the new publication.

The State of the Earth’s Cryosphere represents an extensive collaboration among 20 glaciologists from the United States and three other nations (Canada, Denmark, and Norway) who represent 14 scientific institutions. Since 1988, more than 110 scientists from 24 countries have contributed to the 11-volume series, Satellite Image Atlas of Glaciers of the World (USGS Professional Paper 1386A-K).

The goal of Satellite Image Atlas of Glaciers is to establish a comprehensive baseline of glacier conditions on all continents so that subsequent change can be readily seen and investigated. The advent of spaced-based Earth observation satellites — beginning with the first Landsat satellite in 1972 and continuing with the forthcoming launch of Landsat 8 — made that sweeping objective feasible.

Full Citation

Williams, R.S., Jr., and Ferrigno, J.G., 2012, State of the Earth’s Cryosphere at the Beginning of the 21st Century: Glaciers, Global Snow Cover, Floating Ice, and Permafrost and Periglacial Environments: U.S. Geological Survey Professional Paper 1386-A, 496 p. (with a Plate of the “Earth’s Dynamic Cryosphere,” and a set of eight “Supplemental Cryosphere Notes” about the “Earth’s Dynamic Cryosphere and the Earth System”).

Learn More

Image gallery for State of the Cryosphere

Other volumes of Satellite Image Atlas of Glaciers of the World

Landsat Image Mosaic of Antarctica (LIMA)

Coastal-Change and Glaciological Maps of Antarctica (I-Map 2600 series)

Tucked inside the rocket payload fairing, the next Landsat satellite is ready to ride into space at Vandenberg AFB, CA. Courtesy of NASA.

Currently known as NASA’s Landsat Data Continuity Mission (LDCM), the satellite will be renamed Landsat 8 after three months of extensive testing.  Operational control will then be transferred to USGS.

Landsat 8 will extend the longest continuous and comprehensive record of the Earth’s land as viewed from space. As the world’s population surpasses seven billion people, the impact of human society on the planet is increasing. The continuation of Landsat’s four-decade look at Earth will help monitor those impacts and more accurately forecast future environmental change.

Seeing beyond human sight

Landsat data can assist a broad range of specialists in managing the world’s food, water, forests, and other natural resources for a growing world population.

Landsat images from space are not just pictures. They contain many layers of data collected at different points along the visible and invisible light spectrum. Consequently, Landsat images can show where vegetation is thriving and where it is stressed, where droughts are occurring, where wildland fire is a danger, and where erosion has altered coastlines or river courses.

Landsat satellites give us a view as broad as 12,000 square miles per scene while describing land cover in units the size of a baseball diamond. From a distance of more than 400 miles above the earth surface, a single Landsat scene can record the condition of hundreds of thousands of acres of grassland, agricultural crops, or forests.

Landsat images reveal subtle, gradual changes, such as Wyoming rangelands greening up after a drought, as well as massive landscape changes that occur in rapidly growing urban areas. Landsat can also provide broad assessments of sudden natural or human-induced disasters, such as the number of acres charred by a forest fire or the extent of tsunami inundation. Landsat data have been used to monitor water quality, glacier recession, sea ice movement, invasive species encroachment, coral reef health, land use change, deforestation rates, and population growth.

Free data for innovation

The Wallow Fire, named for the Bear Wallow Wilderness area where the fire originated, was the biggest fire recorded in Arizona. Nearly 6,000 people were evacuated. Landsat 7, June 7, 2011.

The Department of the Interior (DOI) policy of unrestricted access and free distribution of Landsat data encourages researchers everywhere to develop practical applications of the data.  Specific, purpose-driven applications of Landsat data can serve commercial endeavors in agriculture and forestry; they can enable land managers in and out of government to work more efficiently; they can assist scientists in defining and assessing critical environmental issues.

With its long-term historical record of the entire globe and widely recognized high quality of data, Landsat is valued all over the world as the gold standard of land observation. Ready access to authoritative Landsat images provides a reliable common record of Earth conditions that advances the mutual understanding of environmental challenges by citizens, researchers, and decision makers around the globe.

Interior and Landsat from the start

In 1966, at the start of the Landsat era, Interior Secretary Stewart Udall announced Interior’s new Project EROS, the acronym for Earth Resources Observation Satellites. In a statement that echoes to this day, Udall said, “…the time is now right and urgent to apply space technology towards the solution of many pressing natural resources problems being compounded by population and industrial growth.”   2007 video

Udall’s announcement was a catalyst for what eventually became the world’s first civilian land-imaging satellite, developed by NASA and launched on July 23, 1972.

USGS role in observing Earth

Mississippi River flooding near Memphis, Tenn., 2011. The 2006 image (left) shows the river in a more normal state, while the 2011 image (right) shows massive flooding. Landsat 5.

USGS and NASA have distinct roles in the Landsat program. NASA develops remote-sensing instruments and spacecraft, launches satellites, and validates their performance. The USGS then assumes ownership and operation of the satellites, in addition to managing ground-data reception, archiving, product generation, and distribution.

USGS has managed the operations of two Earth observing satellites — Landsat 5 and 7 — for over a decade.  Recently, USGS announced that, after nearly three decades of service, Landsat 5 would be decommissioned over the coming months, bringing to a close the longest-operating Earth observing satellite mission in history.

Launched in 1984, Landsat 5 orbited the planet over 150,000 times while transmitting over 2.5 million images of land surface conditions around the world, long outliving its original three-year design life.

Vital observations by Landsat 5 of the Mount Saint Helens eruption, Antarctica, the Kuwaiti oil fires, the Chernobyl disaster, rainforest depletion, major wildfires and floods, urban growth, global crop production, and ice shelf expansion and retreat have helped increase our understanding and awareness of the impact of humans on the land.

Landsat 7, launched in 1999, continues to provide daily information about our planet from space, although an instrument problem reduces the amount of data it collects.

Observing tomorrow

The LDCM/Landsat 8 satellite carries two instruments, the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS). Advanced technology increases the reliability and sensitivity of these instruments, while the improved measurements are still compatible with the past Landsat data record.

The technical capabilities of LDCM/Landsat 8 move forward in three areas in comparison to Landsat 7:  increased spectral coverage; higher data precision  (the ultimate resolution is not changed); and increased quantity of data collection (60% more scenes per day).  Landsat 8 will orbit Earth once every 99 minutes at an average altitude of 438 miles (705 kilometers),  repeating the same ground track every 16 days.

Landsat 8 data is expected to be available within 100 days of launch from the USGS data archive.

Watching the launch

Further information

USGS Landsat Missions (latest satellite status and related information)

Landsat Data Continuity Mission (NASA)

Landsat: A Global Imaging Program (USGS Fact Sheet)

NASA-USGS 40^th Anniversary of Landsat (July 2012)

Earth as Art (a collection of Landsat scenes created for aesthetic purposes)

BBC interview on Landsat with Matt Larsen, USGS Associate Director

Landsat history (NASA)

What is the Economic Value of Satellite Imagery? (USGS Professional Paper)

The next Landsat satellite: The Landsat Data Continuity Mission (scholarly article)

The world’s longest-running Earth-observing satellite program — Landsat — turns 40.

The world’s longest-running Earth-observing satellite program — Landsat — is 40 years old.

NASA — working in cooperation with the U.S. Department of the Interior (DOI) and its science agency, the USGS — launched the first Landsat satellite on July 23, 1972. The resulting 40-year archive of Earth observations from the Landsat fleet forms an impartial, comprehensive, and easily accessed register of human and natural changes on the land.

Remote-sensing satellites, such as the Landsat series, help scientists to observe the world beyond the power of human sight, to monitor changes, and to detect critical trends in the conditions of natural resources. Data supplied by Landsat supports the improvement of human and environmental health, energy and water management, urban planning, disaster recovery, and crop monitoring.

Through 40 years of continuous coverage, the Landsat series of Earth observation satellites has become a fundamental global reference for scientific issues related to land use and natural resources. Landsat is valued all over the world as the gold standard of land observation. No other satellite program, in our nation or in any other country, comes close to having the historical length and breadth, the continuity and the coverage, of the Landsat archive.

A Versatile Perspective

Landsat satellites can give us a view as broad as 12,000 square miles per scene while characterizing land cover in units the size of a baseball diamond. In one instant look from over 400 miles in space, a single Landsat scene can record the condition of hundreds of thousands of acres of grassland, agricultural crops, or forests.

A comparison of the images illustrates the significant growth in the greater D.C. area. Major urban development can be seen the surrounding communities of Rockville, Greenbelt, and Suitland, Maryland. The expanded Woodrow Wilson Bridge, connecting Springfield, Virginia, with Oxon Hill, Maryland, is evident. The record of surface change is used by urban planners and local officials to evaluate the rate and direction of growth in the area.

Landsat images from space are not just pictures. They contain many layers of data collected at different points along the visible and invisible light spectrum. Consequently, Landsat images can show where vegetation is thriving and where it is stressed, where droughts are occurring, where wildland fire is a danger, and where erosion has altered coastlines or river courses.

Landsat images reveal subtle, gradual changes, such as Wyoming rangelands greening up after a drought, as well as massive landscape changes that occur in rapidly growing urban areas. Landsat can also provide inexpensive assessments of sudden natural or human-induced disasters, such as the number of acres charred by a forest fire or the extent of tsunami inundation.

Impartial information freely available

The Department of the Interior’s policy of releasing the full Landsat archive at no cost allows everyone to have access to this important resource, allowing researchers in the private sector and at universities to generate even more data applications — applications that serve commercial endeavors in agriculture and forestry, that enable land managers in and out of government to work more efficiently, and that define and tackle critical environmental issues.

Landsat and innovation

Landsat has sparked innovation in Earth systems research and in commercial applications of the data from its inception in the mid-1960s.  Since 2008, when Landsat images were made available free of charge, there has been a remarkable burst of innovative science applications of the data.

For example, Landsat data played a central role in an award-winning type of mapping that tracks water use. Using Landsat imagery supplied by USGS in combination with ground-based water data, the Idaho Department of Water Resources and the University of Idaho developed a novel method to create water-use maps that are accurate to the scale of individual fields. Water-use maps help save taxpayer money by increasing the accuracy and effectiveness of public decisions involving water — for instance, in monitoring compliance with legal water rights. In 2009, the Kennedy School of Government at Harvard University cited Idaho’s original design for these maps as an outstanding innovation in American government.

The National Land Cover Database (NLCD 2006) produced by USGS and the federal interagency Multi‑Resolution Land Characteristics Consortium (MRLC) from Landsat imagery is a massive database that describes the surface condition of each 30-meter cell of land in the conterminous U.S. One such cell is approximately the area of a baseball diamond. The range and accuracy of the database enables land managers, urban planners, agricultural experts, and scientists with many different interests (for instance, climate change or invasive species) to identify critical characteristics of the land for a wide variety of investigations.

In the beginning

By the mid-1960s, some civilian geologists, geographers, and agronomists were familiar with imaging potential of classified Earth-observing satellites and had also studied the surprisingly detailed land-surface photos taken by early astronauts using hand-held cameras.

In 1966, with NASA still heavily committed to the Apollo Program in preparation for what would be a 1969 moon landing, the USGS convinced Interior Secretary Stewart Udall to hold a press conference announcing Interior’s new Project EROS, the acronym for Earth Resources Observation Satellites, and, furthermore, that Interior’s first satellite would launch in 1969!

In a statement that echoes true to this day, Udall said, “…the time is now right and urgent to apply space technology towards the solution of many pressing natural resources problems being compounded by population and industrial growth.” This bold announcement succeeded as a catalyst for what eventually became the world’s first civilian land-imaging satellite, developed by NASA and launched on July 23, 1972.

Six years earlier, Udall had said the satellite would be “…just the beginning of a great decade in land and resource analysis for a burgeoning population.”  Today we celebrate not one but four great decades in Earth science from space.

USGS created the “Earth as Art” series to provide a unique avenue of insight about the geography of selected Landsat scenes that have an artistic resonance. This image is titled “Malaspina Glacier.” The tongue of the Malaspina Glacier, the largest glacier in Alaska, fills most of this image. The Malaspina lies west of Yakutat Bay and covers 1,500 sq mi (3,880 sq km).

On the horizon

NASA is preparing to launch the next Landsat satellite, the Landsat Data Continuity Mission (LDCM), on February 11, 2013, from Vandenberg Air Force Base in California. LDCM will be the most technologically advanced satellite in the Landsat series. LDCM sensors take advantage of evolutionary advances in detector and sensor technologies to improve performance and increase reliability. Once it successfully achieves orbit, LDCM will join the Landsat 5 and Landsat 7 satellites as Landsat 8 to continue the Landsat data record.

Join the celebration

NASA and USGS held a news conference,  July 23, to highlight the accomplishments of the Landsat program at the Newseum in Washington, DC.

NASA Television and the NASA website provided live briefing coverage and will maintain archived video of the event. Visit NASA TV or NASA Goddard Multimedia.

For information about “Landsat at 40” anniversary features:

• 10 most significant images from the Landsat record;
• U.S. regions selected for the “My American Landscape” contest;
• announcement of the top five Landsat “Earth As Art” images,visit NASA Landsat.

For details about the Landsat program, including current operations and situational updates, visit USGS Landsat.

Ice Waves. Along the southeastern coast of Greenland, an intricate network of fjords funnels glacial ice to the Atlantic Ocean. Landsat 7 Image.

During a span of 40 years, since 1972, the Landsat series of Earth observation satellites has become a vital reference worldwide for understanding scientific issues related to changes on the Earth’s surface.

To celebrate the 40th Anniversary of Landsat, the U.S. Geological Survey (USGS) and the National Aeronautics and Space Administration (NASA) would like your help in selecting the top five “Earth as Art” images from the more than 120 images in the collection.

The poll is now open and will close on July 6.

Learn more and get details on how to cast your vote.

The top five “Earth as Art” images will be announced on July 23 in Washington, D.C. at a special event commemorating the launch of the first Landsat satellite.

Information as Art

Built by NASA and operated by the USGS, Landsat satellites supply Earth scientists, land-resource managers, and policy makers with objective data about changes across the global landscape. Some changes, like major floods or volcanic eruptions, come quickly; others, like urban sprawl or regrowth from forest fires, appear gradually. Landsat impartially records these and many other changes to the land that are induced by people or nature.

Beyond the scientific information they confer, some Landsat images are simply striking to look at — presenting spectacular views of mountains, valleys, and islands; forests, grasslands, and agricultural patterns. By selecting certain features and coloring them from a digital palate, the USGS has created a series of “Earth as Art” perspectives that demonstrate an artistic resonance in land imagery and provide a special avenue of insight about the geography of each scene.

NASA is preparing to launch the next Landsat satellite in 2013, which will be turned over to USGS for operations and data distribution.

The Lena River, some 2,800 miles (4,500km) long, is one of the largest rivers in the world. The Lena Delta Reserve is the most extensive protected wilderness area in Russia. It is an important refuge and breeding grounds for many species of Siberian wildlife. Landsat 7 Image.

More Information

Earth as Art Image Gallery

Earth as Art at the Library of Congress (exhibit extended through August 31, 2012)

USGS Landsat

NASA Landsat

Contest URL:  http://eros.usgs.gov/eaa_voting/

This stretch of Iceland's northern coast resembles a tiger's head complete with stripes of orange, black, and white. The tiger's mouth is the great Eyjafjorour, a deep fjord that juts into the mainland between steep mountains. The name means "island fjord," derived from the tiny, tear-shaped Hrisey Island near its mouth. The ice-free port city of Akureyri lies near the fjord's narrow tip, and is Iceland's second largest population center after the capital, Reykjavik. Landsat 7 Image.

The U.S. Geological Survey and the United Nations Educational, Scientific and Cultural Organization (UNESCO) have produced a book that gives us a new way to look at our shared global heritage. From Space to Place: An Image Atlas of World Heritage Sites on the ‘In Danger’ List demonstrates an important scientific tool — remote sensing by Earth observing satellites — that helps us understand and manage the physical world we live in.

It is also a visually stunning book that depicts some of the most world’s most notable places.

Mario Hernandez of UNESCO, one of the book’s authors, says the atlas is the result of a fruitful collaboration between the two organizations. “UNESCO and USGS have been working closely to advance the idea of Space for Heritage – the use of space technologies and satellite imagery for the assessment and management of World Heritage sites.  The From Space to Place atlas is a beautiful and useful product from that collaboration.”

In 1972, UNESCO adopted a treaty that calls on the international community to recognize and protect specific places designated as “World Heritage Sites.”  These sites, chosen for their outstanding universal value, may be masterpieces of human creative genius; testimony to cultural tradition or civilizations both living and disappeared; they may contain superlative natural phenomena or exceptional natural beauty and aesthetic importance; or they may house important natural habitats for conservation of biological diversity.

Roger Sayre, the book’s lead author and a senior scientist in the USGS Climate and Land-Use Change Program, says World Heritage sites “are some of the most globally important natural and cultural treasures on Earth,” and adds that “satellite imagery is a valuable data resource that researchers and managers can use to understand threats to these areas, and improve their management.”

Using Satellites to Aid World Heritage

From Space to Place uses satellite imagery to create an atlas depicting the 31 sites on the List of World Heritage in Danger, which are threatened by both human and natural factors. Because not all threats can be seen with satellite images, the editors offer more detailed photos showing a specific feature or species.

“This book shows the many ways satellite imagery helps us assess our environment,” says Anne Castle, Assistant Secretary for Water and Science at the Department of the Interior.  “There is considerable scientific value in the Landsat imagery we have amassed for this project, which we are hopeful will be of great value to the managers and governmental owners of these critical and unbelievably beautiful places.”

Place and History

Much of human history is made up of intangible elements like human actions and activities, philosophical and academic theories, and events both big and small that cannot be recaptured. But many of these ephemeral pieces of our collective memory are embodied by tangible structures and physical features that endure after a moment has passed. These sites may be political monuments like Independence Hall in the United States, or great architectural or artistic achievements like Spain’s Works of Antoni Gaudi or France’s Chartres Cathedral. They may be places that witnessed history both tragic and triumphant like Auschwitz Birkenau or Athens’ Acropolis. They may simply stun us with their natural beauty and scale, like Sumatra’s tropical rainforest or Australia’s Great Barrier Reef. These places – all on UNESCO’s list of World Heritage Sites — are touchstones that we inherit and leave behind; they help us map our universal history.

But not just one type of satellite could tell the full visual story of these places. In the atlas, Landsat imagery combines with other higher resolution images from the Quickbird, Ikonos, Corona and Worldview satellites to show a bird’s eye view of the sites in context with their surrounding environment, giving us a broader perspective on how to understand, protect and manage these treasures.  Other imagery from the Terra and Aqua satellites show coarser pictures, but have a higher temporal frequency, providing imagery of the same location every other day, as opposed to every 16 days for Landsat.

Here are some key examples of those places in From Space to Place.

Garamba National Park

A Landsat image of Garamba National Park in the Democratic Republic of the Congo shows a diverse mosaic of colors representing the many types of habitat that give charismatic animals like the African elephant, giraffe, and hippopotamus a home in the park. Shades of green show different types of forest, while red and brown areas depict savannah grasslands. UNESCO put the park, one of Africa’s oldest protected areas, on the “In Danger” list” in 1996. Threats include limited management, poaching, civil unrest and species decline.

Two moderate resolution (30 m) Landsat 7 ETM+ satellite images taken in 2002 show the extent of Garamba National Park in the Democratic Republic of the Congo and indicate the variety of multicolor habitats it contains.

Abu Mena Archaeological Area

Egypt’s Abu Mena Archaeological Area, which contains remains of an early Christian holy settlement. Built over Menas of Alexandria’s tomb, a martyr who died in AD 296, the site was added to the list in 2001. The view from the Landsat satellite shows the former pilgrimage center in context of its modern surroundings marked by human settlement and agricultural production. Irrigation has transformed the landscape and changed the region’s long-term hydrology, making soil soft and unstable and dissolving the clay that supports the site’s buildings, which now are in risk of collapse.

A pair of moderate resolution (30 m) natural color Landsat images of the area around Abu Mena, in Egypt, from 1984 and 2001 show how the landscape around the site changed in that 17-year period. The site has become completely surrounded by irrigated agricultural development.

In the United States

The United States is home to 21 World Heritage sites, none of which are on the “In Danger” list. Still, this atlas provides an example of how satellite imagery improves our way of looking at the places that define our country. From the Statue of Liberty to the Grand Canyon, and from the Everglades to the Hawaii Volcanoes National Park, we can use space technology and scientific understanding to manage our shared national treasures.